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Search: WFRF:(Mani Katrin)

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1.
  • Mani, Katrin, et al. (author)
  • HIV-Tat protein transduction domain specifically attenuates growth of polyamine deprived tumor cells.
  • 2007
  • In: Molecular Cancer Therapeutics. - 1538-8514. ; 6:2, s. 782-788
  • Journal article (peer-reviewed)abstract
    • Polyamines are essential for tumor cell growth, and the polyamine pathway represents an attractive target for cancer treatment. Several polyamine transport proteins have been cloned and characterized in bacteria and yeast cells; however, the mechanism of polyamine entry into mammalian cells remains poorly defined, although a role for proteoglycans has been suggested. Here, we show that the HIV-Tat transduction peptide, which is known to enter cells via a proteoglycan-dependent pathway, efficiently inhibits polyamine uptake. Polyamine uptake–deficient mutant cells with intact proteoglycan biosynthesis (CHO MGBG) displayed unperturbed HIV-Tat uptake activity compared with wild-type cells, supporting the notion that HIV-Tat peptide interferes with polyamine uptake via competition for proteoglycan binding sites rather than a putative downstream transporter. HIV-Tat specifically inhibited growth of human carcinoma cells made dependent on extracellular polyamines by treatment with the polyamine biosynthesis inhibitor {alpha}-difluoromethylornithine; accordingly, the Tat peptide prevented intracellular accumulation of exogenous polyamines. Moreover, combined treatment with {alpha}-difluoromethylornithine and HIV-Tat efficiently blocked tumor growth in an experimental mouse model. We conclude that HIV-Tat transduction domain and polyamines enter cells through a common pathway, which can be used to target polyamine-dependent tumor growth in the treatment of cancer.
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2.
  • Abdelhady, Wael Awad, et al. (author)
  • GPC1 (glypican 1)
  • 2014
  • In: Atlas of Genetics and Cytogenetics in Oncology and Haematology. - : INIST-CNRS. - 1768-3262. ; 18:7, s. 461-464
  • Journal article (peer-reviewed)abstract
    • Review on GPC1, with data on DNA/RNA, on the protein encoded and where the gene is implicated.
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3.
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4.
  • Abrahamsson, Carl-Olof, et al. (author)
  • Xylosylated naphthoic acid-amino acid conjugates for investigation of glycosaminoglycan priming.
  • 2008
  • In: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 343:9, s. 1473-1477
  • Journal article (peer-reviewed)abstract
    • Three different series of xylosylated naphthoic acid-amino acid conjugates containing one or two amino acid residues were synthesized for the investigation of glycosaminoglycan priming and potential use as anti-tumor drugs. All xylosylated naphthoic acid-conjugates inhibited the growth of normal lung fibroblasts to some extent, whereas the growth of tumor derived T24 carcinoma cells was not affected. There was no correlation between amino acid conjugation, retention time and the antiproliferative activity. Only one compound initiated the priming of glycosaminoglycans. Modification of the naphthalene ring with one or two amino acid residues did not have any effect on proteoglycan biosynthesis or glycosaminoglycan priming in T24 carcinoma cells.
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5.
  • Aili, Ulrika, et al. (author)
  • Antiproliferative effects of peracetylated naphthoxylosides.
  • 2009
  • In: Bioorganic & Medicinal Chemistry Letters. - : Elsevier BV. - 0960-894X. ; 19, s. 1763-1766
  • Journal article (peer-reviewed)abstract
    • The antiproliferative activity, and the capability of priming of glycosaminoglycan chains, of two series of peracetylated mono- and bis-xylosylated dihydroxynaphthalenes have been investigated for normal HFL-1 cells, as well as transformed T24 cells, and compared to the unprotected analogs. Our data show increased antiproliferative activity upon peracetylation, but a loss of selectivity towards T24 cells.
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6.
  • Aili, Ulrika, et al. (author)
  • Attenuation of tumor growth by formation of antiproliferative glycosaminoglycans correlates with low acetylation of histone H3.
  • 2010
  • In: Cancer Research. - 1538-7445. ; 70:9, s. 3771-3779
  • Journal article (peer-reviewed)abstract
    • Glycosaminoglycan (GAG) chains anchored to core proteins form proteoglycans, widely distributed cell-surface macromolecules with multiple functions, such as regulation of growth factor and cytokine signaling, cell-cell interactions, and uptake of biomolecules. The biosynthesis of GAG can be manipulated by xylosides attached to various hydrophobic groups, and we have earlier reported that a naphthoxyloside, 2-(6-hydroxynaphthyl) beta-D-xylopyranoside (XylNapOH), which serves as a primer for GAG synthesis, reduces tumor load up to 97% in vivo, despite lower efficiency in vitro. Here we show, using radiolabeled xylosides and coculture experiments, that XylNapOH-treated bladder and breast carcinoma cells secrete antiproliferative GAG chains that are taken up by both normal and cancer cells and transported to the cell nuclei where they induce an antiproliferative effect, accompanied by apoptosis. We also show that XylNapOH treatment lowers the level of histone H3 acetylation selectively in bladder and breast carcinoma cells without affecting expression of histone H3. However, XylNapOH-primed GAG chains from normal cells are not internalized and do not cause growth retardation. Using in vitro and in vivo C6 glioma cell and tumor models, we show that XylNapOH is much more effective in vivo than in vitro. We propose that, in vivo, the antiproliferative XylNapOH-primed GAG chains produced by tumor cells inhibit tumor growth in an autocrine fashion by formation of antiproliferative GAG chains on the xyloside prodrug, whereas no antiproliferative GAG chains are produced by surrounding normal cells. This is a novel mechanism for targeting tumor cells, making these xylosides promising drug candidates for antitumor therapy.
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7.
  • Awad, Wael, et al. (author)
  • Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration.
  • 2013
  • In: Acta Crystallographica. Section D: Biological Crystallography. - 1399-0047. ; 69:Pt 12, s. 2524-2533
  • Journal article (peer-reviewed)abstract
    • The use of controlled dehydration for improvement of protein crystal diffraction quality is increasing in popularity, although there are still relatively few documented examples of success. A study has been carried out to establish whether controlled dehydration could be used to improve the anisotropy of crystals of the core protein of the human proteoglycan glypican-1. Crystals were subjected to controlled dehydration using the HC1 device. The optimal protocol for dehydration was developed by careful investigation of the following parameters: dehydration rate, final relative humidity and total incubation time Tinc. Of these, the most important was shown to be Tinc. After dehydration using the optimal protocol the crystals showed significantly reduced anisotropy and improved electron density, allowing the building of previously disordered parts of the structure.
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8.
  • Awad, Wael, et al. (author)
  • Structural and Biophysical Characterization of Human EXTL3 : Domain Organization, Glycosylation, and Solution Structure
  • 2018
  • In: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 57:7, s. 1166-1177
  • Journal article (peer-reviewed)abstract
    • Heparan sulfate proteoglycans are proteins substituted with one or more heparan sulfate (HS) polysaccharides, found in abundance at cell surfaces. HS chains influence the activity of many biologically important molecules involved in cellular communication and signaling. The exostosin (EXT) proteins are glycosyltransferases in the Golgi apparatus that assemble HS chains on HSPGs. The EXTL3 enzyme mainly works as an initiator in HS biosynthesis. In this work, human lumenal N-glycosylated EXTL3 (EXTL3ΔN) was cloned, expressed in human embryonic kidney cells, and purified. Various biophysical and biochemical approaches were then employed to elucidate the N-glycosylation sites and the function of their attached N-glycans. Furthermore, the stability and conformation of the purified EXTL3ΔN protein in solution have been analyzed. Our data show that EXTL3ΔN has N-glycans at least at two positions, Asn290 and Asn592, which seem to be critical for proper protein folding and/or release. EXTL3ΔN is quite stable, as high temperature (∼59 °C) was required for denaturation. Deconvolution of the EXTL3ΔN far-UV CD spectrum revealed a substantial fraction of β sheets (25%) with a minor proportion of α-helices (14%) in the secondary structure. Solution small-angle X-ray scattering and dynamic light scattering revealed an extended structure suggestive of a dimeric arrangement and consisting of two distinct regions, narrow and broad, respectively. This is consistent with bioinformatics analyses suggesting a 3-domain structure with two glycosyltransferase domains and a coiled-coil domain.
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9.
  • Awad, W., et al. (author)
  • Structural Aspects of N-Glycosylations and the C-terminal Region in Human Glypican-1
  • 2015
  • In: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 290:38, s. 22991-23008
  • Journal article (peer-reviewed)abstract
    • Glypicans are multifunctional cell surface proteoglycans involved in several important cellular signaling pathways. Glypican-1 (Gpc1) is the predominant heparan sulfate proteoglycan in the developing and adult human brain. The two N-linked glycans and the C-terminal domain that attach the core protein to the cell membrane are not resolved in the Gpc1 crystal structure. Therefore, we have studied Gpc1 using crystallography, small angle x-ray scattering, and chromatographic approaches to elucidate the composition, structure, and function of the N-glycans and the Cterminus and also the topology of Gpc1 with respect to the membrane. The Cterminus is shown to be highly flexible in solution, but it orients the core protein transverse to the membrane, directing a surface evolutionarily conserved in Gpc1 orthologs toward the membrane, where it may interact with signaling molecules and/or membrane receptors on the cell surface, or even the enzymes involved in heparan sulfate substitution in the Golgi apparatus. Furthermore, the N-glycans are shown to extend the protein stability and lifetime by protection against proteolysis and aggregation.
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10.
  • Belting, Mattias, et al. (author)
  • Glypican-1 is a vehicle for polyamine uptake in mammalian cells. A pivotal role for nitrosothiol-derived nitric oxide.
  • 2003
  • In: Journal of Biological Chemistry. - 1083-351X. ; 278:47, s. 47181-47189
  • Journal article (peer-reviewed)abstract
    • Polyamines (putrescine, spermidine, and spermine) are essential for growth and survival of all cells. When polyamine biosynthesis is inhibited, there is up-regulation of import. The mammalian polyamine transport system is unknown. We have previously shown that the heparan sulfate (HS) side chains of recycling glypican-1 (Gpc-1) can sequester spermine, that intracellular polyamine depletion increases the number of NO-sensitive N-unsubstituted glucosamines in HS, and that NO-dependent cleavage of HS at these sites is required for spermine uptake. The NO is derived from S-nitroso groups in the Gpc-1 protein. Using RNA interference technology as well as biochemical and microscopic techniques applied to both normal and uptake-deficient cells, we demonstrate that inhibition of Gpc-1 expression abrogates spermine uptake and intracellular delivery. In unperturbed cells, spermine and recycling Gpc-1 carrying HS chains rich in N-unsubstituted glucosamines were co-localized. By exposing cells to ascorbate, we induced release of NO from the S-nitroso groups, resulting in HS degradation and unloading of the sequestered polyamines as well as nuclear targeting of the deglycanated Gpc-1 protein. Polyamine uptake-deficient cells appear to have a defect in the NO release mechanism. We have managed to restore spermine uptake partially in these cells by providing spermine NONOate and ascorbate. The former bound to the HS chains of recycling Gpc-1 and S-nitrosylated the core protein. Ascorbate released NO, which degraded HS and liberated the bound spermine. Recycling HS proteoglycans of the glypican-type may be plasma membrane carriers for cargo taken up by caveolar endocytosis.
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11.
  • Cappai, Roberto, et al. (author)
  • The amyloid precursor protein(APP)of Alzheimer's disease and its paralog APLP2 modulate the Cu/Zn-NO-catalyzed degradation of glypican-1 heparan sulfate In vivo.
  • 2005
  • In: Journal of Biological Chemistry. - 1083-351X. ; 280:14, s. 13913-13920
  • Journal article (peer-reviewed)abstract
    • Processing of the recycling proteoglycan glypican-1 involves the release of its heparan sulfate chains by copper ion- and nitric oxide-catalyzed ascorbate-triggered autodegradation. The Alzheimer disease amyloid precursor protein (APP) and its paralogue, the amyloid precursor-like protein 2 (APLP2), contain copper ion-, zinc ion-, and heparan sulfate-binding domains. We have investigated the possibility that APP and APLP2 regulate glypican-1 processing during endocytosis and recycling. By using cell-free biochemical experiments, confocal laser immunofluorescence microscopy, and flow cytometry of tissues and cells from wild-type and knock-out mice, we find that (a) APP and glypican-1 colocalize in perinuclear compartments of neuroblastoma cells, (b) ascorbate-triggered nitric oxidecatalyzed glypican-1 autodegradation is zinc ion-dependent in the same cells, (c) in cell-free experiments, APP but not APLP2 stimulates glypican-1 autodegradation in the presence of both Cu(II) and Zn(II) ions, whereas the Cu(I) form of APP and the Cu(II) and Cu(I) forms of APLP2 inhibit autodegradation, (d) in primary cortical neurons from APP or APLP2 knock-out mice, there is an increased nitric oxide-catalyzed degradation of heparan sulfate compared with brain tissue and neurons from wild-type mice, and (e) in growth-quiescent fibroblasts from APLP2 knock-out mice, but not from APP knock-out mice, there is also an increased heparan sulfate degradation. We propose that the rate of autoprocessing of glypican-1 is modulated by APP and APLP2 in neurons and by APLP2 in fibroblasts. These observation identify a functional relationship between the heparan sulfate and copper ion binding activities of APP/APLP2 in their modulation of the nitroxyl anion-catalyzed heparan sulfate degradation in glypican-1.
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12.
  • Cheng, Fang, et al. (author)
  • APP/APLP2 expression is required to initiate endosome-nucleus-autophagosome trafficking of glypican-1-derived heparan sulfate.
  • 2014
  • In: Journal of Biological Chemistry. - 1083-351X. ; 289:30, s. 20871-20878
  • Journal article (peer-reviewed)abstract
    • Anhydromannose (anMan)-containing heparan sulfate (HS) derived from the proteoglycan glypican-1 (Gpc-1) is generated in endosomes by an endogenously or ascorbate induced SNO-catalyzed reaction. Processing of the amyloid precursor protein (APP) and APP-like protein 2 (APLP2) by β- and γ-secretases into amyloid beta (Aβ) and Aβ-like peptides also takes place in these compartments. Moreover, anMan-containing HS suppresses the formation of toxic Aβ assemblies in vitro. We show by using deconvolution immunofluorescence microscopy with an anMan-specific monoclonal antibody as well as 35S-labeling experiment that expression of APP/APLP2 is required for ascorbate-induced transport of HS from endosomes to the nucleus. Nuclear translocation was observed in wild-type mouse embryonic fibroblasts (Wt-MEF), Tg2576 MEF and N2a neuroblastoma cells but not in APP-/- and APLP2-/- MEF. Transfection of APP-/- cells with a vector encoding APP restored nuclear import of anMan-containing HS. In Wt-MEF and N2a neuroblastoma cells exposed to β- or γ-secretase inhibitors, nuclear translocation was greatly impeded, suggesting involvement of APP/APLP2 degradation products. In Tg2576 MEF, the β-inhibitor blocked transport but the γ- inhibitor did not. During chase in ascorbate-free medium, anMan-containing HS disappeared from the nuclei of Wt-MEF. Confocal immunofluorescence microscopy showed that they appeared in acidic, LC3-positive vesicles in keeping with an autophagosomal location. There was increased accumulation of anMan-containing HS in nuclei and cytosolic vesicles upon treatment with chloroquine indicating that HS was degraded in lysosomes. Manipulations of APP expression and processing may have deleterious effects upon HS function in the nucleus.
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13.
  • Cheng, Fang, et al. (author)
  • Attenuation of cancer proliferation by suppression of glypican-1 and its pleiotropic effects in neoplastic behavior
  • 2023
  • In: Oncotarget. - : Impact Journals, LLC. - 1949-2553. ; 14:1, s. 219-235
  • Journal article (peer-reviewed)abstract
    • Glypicans (GPC1-6) are associated with tumorigenic processes and their involvement in neoplastic behavior has been discussed in different cancer types. Here, a cancer-wide GPC expression study, using clinical cancer patient data in The Cancer Genome Atlas, reveals net upregulation of GPC1 and GPC2 in primary solid tumors, whereas GPC3, GPC5 and GPC6 display lowered expression pattern compared to normal tissues. Focusing on GPC1, survival analyses of the clinical cancer patient data reveal statistically significant correlation between high expression of GPC1 and poor prognosis in 10 particular cancer types i.e., bladder urothelial carcinoma, brain lower grade glioma, liver hepatocellular carcinoma, colon adenocarcinoma, kidney renal clear cell carcinoma, lung adenocarcinoma, mesothelioma, ovarian serous cystadenocarcinoma, uterine corpus endometrial carcinoma and uveal melanoma. In vitro studies targeting GPC1 expression by CRISPR/Cas9 or siRNA or treatment with an anti-GPC1 antibody resulted in attenuation of proliferation of cancer cells from bladder carcinoma, glioma and hepatocellular carcinoma patients (T24, U87 and HepG2 cells). Further, overexpression of GPC1 exhibited a significant and negative correlation between GPC1 expression and proliferation of T24 cells. Attempt to reveal the mechanism through which downregulation of GPC1 leads to attenuation of tumor growth using systematic Ingenuity Pathway Analysis indicate that suppression of GPC1 results in ECM-mediated inhibition of specific pro-cancer signaling pathways involving TGF-β and p38 MAPK. Identified differential expression and pleiotropic effects of GPCs in specific cancer types emphasize their potential of as novel diagnostic tools and prognostic factors and open doors for future GPC targeted therapy.
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14.
  • Cheng, Fang, et al. (author)
  • Common traffic routes for imported spermine and endosomal glypican-1-derived heparan sulfate in fibroblasts
  • 2018
  • In: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 364:2, s. 133-142
  • Journal article (peer-reviewed)abstract
    • Import of the polyamine spermine from the extracellular environment depends on the presence of cell surface heparan sulfate proteoglycans, such as glypican-1. This proteoglycan is internalized by endocytosis, releases its heparan sulfate chains in endosomes by a nitric oxide-, copper- and amyloid precursor protein-dependent mechanism, then penetrates the membrane and is transported to the nucleus and then to autophagosomes. This process is spontaneous or induced by ascorbate depending on the growth-state of the cell. Here, we have explored possible connections between the heparan sulfate traffic route and spermine uptake and delivery in wild-type and Tg2576 mouse fibroblasts. Cells were examined by deconvolution immunofluorescence microscopy. The antibodies used were specific for spermine, glypican-1-derived heparan sulfate, Rab7, nucleolin and a marker for autophagosomes. Endogenous immunostainable spermine was primarily associated with autophagosomes. When spermine synthesis was inhibited, imported spermine appeared in Rab7-positive endosomes. When ascorbate was added, heparan sulfate and spermine were transported to the nucleus where they colocalized with nucleolin. Spermine also appeared in autophagosomes. In a pulse-chase experiment, heparan sulfate and spermine were first arrested in late endosomes by actinomycin D treatment. During the chase, when arrest was abolished, heparan sulfate and spermine were both transported to the nucleus and targeted nucleolin. In amyloid precursor protein-/--fibroblasts, ascorbate failed to induce release of heparan sulfate and spermine remained in the endosomes. We propose that cell surface glypican-1 carries spermine to the endosomes and that the released heparan sulfate carries spermine across the membrane into the cytosol and then to the nucleus.
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15.
  • Cheng, Fang, et al. (author)
  • Complex modulation of cytokine-induced α-synuclein aggregation by glypican-1-derived heparan sulfate in neural cells
  • 2022
  • In: Glycobiology. - : Oxford University Press (OUP). - 0959-6658 .- 1460-2423. ; 32:4, s. 333-342
  • Journal article (peer-reviewed)abstract
    • In Parkinson's disease (PD), there is accumulation of α-synuclein (SYN) aggregates in neurons, which is promoted by neuroinflammation. The cytokines TNF-α, IL-1β and IL-6 induce accumulation of degradation products of the amyloid precursor protein (APP) combined with heparan sulfate (HS) chains released from glypican-1 (Gpc-1) by NO-dependent cleavage. We have investigated the effects of the cytokines and HS on SYN aggregation and secretion in dividing human neuroblastoma (SH-SY5Y) and inducible neural progenitor cells (NPC) by using immunofluorescence microscopy, vesicle isolation and slot blotting with antibodies recognizing SYN monomers and aggregates, Gpc-1, the released HS, endosomes, and autophagosomes. In SH-SY5Y cells, the capacity to release HS was fully utilized, while NPC displayed dormant capacity. TNF-α induced increased formation of SYN aggregates and clustering of HS in SH-SY5Y cells. When the supply of NO was simultaneously increased, SYN and HS accumulation disappeared. When NO formation was inhibited, SYN and HS aggregation also disappeared, but there was now a 4-fold increase in SYN secretion. In NPC, IL-6 induced increased aggregation of SYN and stimulated HS release from Gpc-1. Both SYN and HS co-localized with autophagosome marker. When HS-deficient Gpc-1 was simultaneously generated, by using a cyanobacterial neurotoxin, accumulation diminished and there was massive secretion of SYN. We suggest that the cytokines increase APP processing, which initiates NO-dependent release of HS from Gpc-1. The APP degradation products also trigger SYN aggregation. As HS can inhibit APP processing, HS-or NO-deficiency may result in autophagosomal dysfunction and both APP degradation products and SYN are secreted.
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16.
  • Cheng, Fang, et al. (author)
  • Copper-dependent co-internalization of the prion protein and glypican-1.
  • 2006
  • In: Journal of Neurochemistry. - : Wiley. - 1471-4159 .- 0022-3042. ; 98:5, s. 1445-1457
  • Journal article (peer-reviewed)abstract
    • Heparan sulfate chains have been found to be associated with amyloid deposits in a number of diseases including transmissible spongiform encephalopathies. Diverse lines of evidence have linked proteoglycans and their glycosaminoglycan chains, and especially heparan sulfate, to the metabolism of the prion protein isoforms. Glypicans are a family of glycosylphosphatidylinositol-anchored, heparan sulfate-containing, cell-associated proteoglycans. Cysteines in glypican-1 can become nitrosylated by endogenously produced nitric oxide. When glypican-1 is exposed to a reducing agent, such as ascorbate, nitric oxide is released and autocatalyses deaminative cleavage of heparan sulfate chains. These processes take place while glypican-1 recycles via a non-classical, caveolin-associated pathway. We have previously demonstrated that prion protein provides the Cu2+ ions required to nitrosylate thiol groups in the core protein of glypican-1. By using confocal immunofluorescence microscopy and immunomagnetic techniques, we now show that copper induces co-internalization of prion protein and glypican-1 from the cell surface to perinuclear compartments. We find that prion protein is controlling both the internalization of glypican-1 and its nitric oxide-dependent autoprocessing. Silencing glypican-1 expression has no effect on copper-stimulated prion protein endocytosis, but in cells expressing a prion protein construct lacking the copper binding domain internalization of glypican-1 is much reduced and autoprocessing is abrogated. We also demonstrate that heparan sulfate chains of glypican-1 are poorly degraded in prion null fibroblasts. The addition of either Cu2+ ions, nitric oxide donors, ascorbate or ectopic expression of prion protein restores heparan sulfate degradation. These results indicate that the interaction between glypican-1 and Cu2+-loaded prion protein is required both for co-internalization and glypican-1 self-pruning.
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17.
  • Cheng, Fang, et al. (author)
  • Cytochrome b561, copper, β-cleaved amyloid precursor protein and niemann-pick C1 protein are involved in ascorbate-induced release and membrane penetration of heparan sulfate from endosomal S-nitrosylated glypican-1
  • 2017
  • In: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 360:2, s. 171-179
  • Journal article (peer-reviewed)abstract
    • Ascorbate-induced release of heparan sulfate from S-nitrosylated heparan sulfate proteoglycan glypican-1 takes place in endosomes. Heparan sulfate penetrates the membrane and is transported to the nucleus. This process is dependent on copper and on expression and processing of the amyloid precursor protein. It remains unclear how exogenously supplied ascorbate can generate HS-anMan in endosomes and how passage through the membrane is facilitated. Here we have examined wild-type, Alzheimer Tg2576 and amyloid precursor protein (-/-) mouse fibroblasts and human fetal and Niemann-Pick C1 fibroblasts by using deconvolution immunofluorescence microscopy, siRNA technology and [S35]sulfate-labeling, vesicle isolation and gel chromatography. We found that ascorbate-induced release of heparan sulfate was dependent on expression of endosomal cytochrome b561. Formation and nuclear transport of heparan sulfate was suppressed by inhibition of β-processing of the amyloid precursor protein and formation was restored by copper (I) ions. Membrane penetration was not dependent on amyloid beta channel formation. Inhibition of endosomal exit resulted in accumulation of heparan sulfate in vesicles that exposed the C-terminal of the amyloid precursor protein externally. Endosome-to-nucleus transport was also dependent on expression of the Niemann-Pick C1 protein. We propose that ascorbate is taken up from the medium and is oxidized by cytochrome b561 which, in turn, reduces copper (II) to copper (I) present in the N-terminal, β-cleaved domain of the amyloid precursor protein. Re-oxidation of copper (I) is coupled to reductive, deaminative release of heparan sulfate from glypican-1. Passage through the membrane may be facilitated by the C-terminal, β-cleaved fragment of the amyloid precursor protein and the Niemann-Pick C1 protein.
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18.
  • Cheng, Fang, et al. (author)
  • Hypoxia induces NO-dependent release of heparan sulfate in fibroblasts from the Alzheimer mouse Tg2576 by activation of nitrite reduction.
  • 2016
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 26:6, s. 623-634
  • Journal article (peer-reviewed)abstract
    • There is a functional relationship between the heparan sulfate proteoglycan glypican-1 and the amyloid precursor protein of Alzheimer disease. In wild-type mouse embryonic fibroblasts, expression and processing of the amyloid precursor protein is required for endosome-to-nucleus translocation of anhydromannose-containing heparan sulfate released from S-nitrosylated glypican-1 by ascorbate-induced, nitrosothiol-catalyzed deaminative cleavage. In fibroblasts from the transgenic Alzheimer mouse Tg2576 there is increased processing of the amyloid precursor protein to amyloid-β peptides. Simultaneously, there is spontaneous formation of anhydromannose-containing heparan sulfate by an unknown mechanism. We have explored the effect of hypoxia on anhydromannose-containing heparan sulfate formation in wild-type and Tg2576 fibroblasts by deconvolution immunofluorescence microscopy and flow cytometry using an anhydromannose-specific monoclonal antibody and by (35)SO4-labeling experiments. Hypoxia prevented ascorbate-induced heparan sulfate release in wild-type fibroblasts, but induced an increased formation of anhydromannose-positive and (35)S-labeled heparan sulfate in Tg2576 fibroblasts. This appeared to be independent of glypican-1 S-nitrosylation as demonstrated by using a monoclonal antibody specific for S-nitrosylated glypican-1. In hypoxic wild-type fibroblasts, addition of nitrite to the medium restored anhydromannose-containing heparan sulfate formation. The increased release of anhydromannose-containing heparan sulfate in hypoxic Tg2576 fibroblasts did not require addition of nitrite. However, it was suppressed by inhibition of the nitrite reductase activity of xanthine oxidoreductase/aldehyde oxidase or by inhibition of p38 mitogen-activated protein kinase or by chelation of iron. We propose that normoxic Tg2576 fibroblasts maintain a high level of anhydromannose-containing heparan sulfate production by a stress-activated generation of nitric oxide from endogenous nitrite. This activation is enhanced by hypoxia.
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19.
  • Cheng, Fang, et al. (author)
  • Interplay between APP and glypican-1 processing and α-synuclein aggregation in undifferentiated and differentiated human neural progenitor cells
  • 2023
  • In: Glycobiology. - : Oxford University Press (OUP). - 0959-6658 .- 1460-2423. ; 33:4, s. 325-341
  • Journal article (peer-reviewed)abstract
    • In Parkinson’s disease, there is an accumulation of α-synuclein (SYN) aggregates in neurons, which is promoted by neuroinflammation. In neural cells, cytokine-induced SYN aggregation is modulated by heparan sulfate (HS) derived from glypican-1 (GPC1) by amyloid precursor protein (APP) and nitric oxide (NO)-dependent cleavage. We have explored possible interplay between APP, GPC1, and SYN in undifferentiated and differentiated neural progenitor cells (NPCs) by modulating APP and GPC1 processing. Effects were monitored by immunofluorescence microscopy and slot immunoblotting using antibodies recognizing APP degradation products, HS released from GPC1, and SYN aggregates (filamentous SYN [SYNfil]). Suppression of HS release from GPC1 by inhibition of β-secretase or by NO deprivation resulted in no or slight increase in SYNfil aggregation. Stimulation of HS release by ascorbate did not further increase SYNfil staining. Interleukin-6 (IL-6) induced increased APP and GPC1 processing and SYNfil formation, which was reduced when βsecretase was inhibited and when HS release was impeded by NO deprivation. Ascorbate restored APP and GPC1 processing but did not affect SYNfil formation. Ascorbate-dependent differentiation of NPC resulted in the expression of tyrosine hydroxylase (TH) which colocalized with SYNfil. Suppression of APP processing by inhibition of β-secretase greatly disturbed the differentiation process. IL-6 induced coclustering of APP-degradation products, TH, HS, and SYNfil, which could be reversed by stimulation of HS release from GPC1 by excess ascorbate. We suggest that continuous release of HS from GPC1 moderates SYN aggregation and supports differentiation of NPC to dopaminergic neurons.
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20.
  • Cheng, Fang, et al. (author)
  • Nitric oxide-dependent processing of heparan sulfate in recycling S-nitrosylated glypican-1 takes place in caveolin-1 containing endosomes.
  • 2002
  • In: Journal of Biological Chemistry. - 1083-351X. ; 277:46, s. 44431-44439
  • Journal article (peer-reviewed)abstract
    • We have previously demonstrated intracellular degradation of the heparan sulfate side-chains in recycling glypican-1 by heparanase and by deaminative cleavage at N-unsubstituted glucosamine with nitric oxide derived from intrinsic nitrosothiols [see Ding, K., Mani, K., Cheng, F., Belting, M. and Fransson, L.-. (2002) J. Biol. Chem., 277, xxx-xxx; prepub M203383200]. To determine where and in what order events take place, we have visualized, by using confocal laser-scanning immunofluorescence microscopy, glypican-1 variants in unperturbed cells or arrested at various stages of processing. In unperturbed proliferating cells, glypican-1 was partly S-nitrosylated. Intracellular glypican-1 was enriched in endosomes, colocalized significantly with GM-1 ganglioside, caveolin-1 and Rab9-positive endosomes, and carried side-chains rich in N-unsubstituted glucosamine residues. However, such residues were scarce in cell-surface glypican-1. Brefeldin A-arrested glypican-1, which was non-S-nitrosylated and carried side-chains rich in N-unsubstituted glucosamines, colocalized extensively with caveolin-1 but not with Rab9. Suramin, which inhibits heparanase, induced the appearance of S-nitrosylated glypican-1 in caveolin-1-rich compartments. Inhibition of deaminative cleavage did not prevent heparanase from generating heparan sulfate oligosaccharides that colocalized strongly with caveolin-1. Growth-quiescent cells displayed extensive NO-dependent deaminative cleavage of heparan sulfate generating anhydromannose-terminating fragments which were partly associated with acidic vesicles. Proliferating cells generated such fragments during polyamine uptake. We conclude that recycling glypican-1 that is associated with caveolin-1-containing endosomes undergoes sequential N-desulfation/N-deacetylation, heparanase cleavage, S-nitrosylation, NO-release and deaminative cleavage of its side-chains in conjunction with polyamine uptake.
  •  
21.
  • Cheng, Fang, et al. (author)
  • Non-conserved, S-nitrosylated cysteines in glypican-1 react with N-unsubstituted glucosamines in heparan sulfate and catalyze deaminative cleavage.
  • 2012
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 22:11, s. 1480-1485
  • Journal article (peer-reviewed)abstract
    • The membrane lipid-anchored glypicans (heparan sulfate proteoglycans) are present in both vertebrates and invertebrates and serve as important modulators of growth factors and morphogens during development. Their core proteins are similar and consist of a large N-terminal domain comprising 14 evolutionary conserved cysteines and a C-terminal stalk carrying the heparan sulfate side-chains and the lipid anchor. Cysteines in glypican-1 can be S-nitrosylated but their positions have not been identified. The recently determined crystal structure of the N-terminal domain of glypican-1 has revealed that all the evolutionary conserved cysteines form intramolecular disulfide bonds. However, glypican-1 contains two more, non-conserved cysteines in the C-terminal stalk, located near the heparan sulfate attachment sites. We show here that the non-conserved cysteines are free thiols as a glypican-1 core protein containing the C-terminal stalk could be biotinylated by biotin-BMCC. After S-nitrosylation by using an NO-donor and copper ions, the glypican-1 core protein was retained on an affinity matrix substituted with heparan sulfate oligosaccharides containing N-unsubstituted glucosamines. The protein was displaced with 0.2 M glucosamine but also by 2 mM ascorbate. In the latter case, the heparan sulfate of the affinity matrix was simultaneously cleaved into fragments containing anhydromannose. We propose that the S-nitrosocysteine residues interact with closely located N-unsubstituted glucosamines in the heparan sulfate side-chains of the glypican-1 proteoglycan. Addition of ascorbate induces a series of reactions that eventually releases heparan sulfate fragments with reducing terminal anhydromannose, presumably without the formation of free nitric oxide.
  •  
22.
  • Cheng, Fang, et al. (author)
  • Non-toxic amyloid beta formed in the presence of glypican-1 or its deaminatively generated heparan sulfate degradation products
  • 2013
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 23:12, s. 1510-1519
  • Journal article (peer-reviewed)abstract
    • The amyloid beta (A beta) peptides (mainly A beta 40 and A beta 42), which are derived from the amyloid precursor protein (APP), can oligomerize into antibody A11-positive, neurotoxic species, believed to be involved in Alzheimer's disease. Interestingly, APP binds strongly to the heparan sulfate (HS) proteoglycan (PG) glypican-1 (Gpc-1) in vitro and both proteins are colocalized inside cells. In endosomes, APP is proteolytically processed to yield A beta peptides. The HS chains of S-nitrosylated (SNO) Gpc-1 PG are cleaved into anhydromannose (anMan)-containing di- and oligosaccharides by an NO-dependent reaction in the same compartments. Here, we have studied the toxicity of oligomers/aggregates of A beta 40 and A beta 42, as well as A beta 40/42 mixtures that were formed in the presence of immobilized Gpc-1 PG or immobilized HS oligosaccharides. Afterwards, A beta was displaced from the matrices, analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and assayed for A11 immunoreactivity, for effects on growth of mouse N2a neuroblastoma cells and for membrane leakage in rat cortical neurons. HS generally promoted and accelerated A beta multimerization into oligomers as well as larger aggregates that were mostly A11 positive and showed toxic effects. However, non-toxic A beta was formed in the presence of Gpc-1 PG or when anMan-containing HS degradation products were simultaneously generated. Both toxic and non-toxic A beta peptides were taken up by the cells but toxic forms appeared to enter the nuclei to a larger extent. The protection afforded by the presence of HS degradation products may reflect a normal intracellular function for the A beta peptides.
  •  
23.
  • Cheng, Fang, et al. (author)
  • Nucleolin is a nuclear target of heparan sulfate derived from glypican-1
  • 2017
  • In: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 354:1, s. 31-39
  • Journal article (peer-reviewed)abstract
    • The recycling, S-nitrosylated heparan sulfate (HS) proteoglycan glypican-1 releases anhydromannose (anMan)-containing HS chains by a nitrosothiol-catalyzed cleavage in endosomes that can be constitutive or induced by ascorbate. The HS-anMan chains are then transported to the nucleus. A specific nuclear target for HS-anMan has not been identified. We have monitored endosome-to-nucleus trafficking of HS-anMan by deconvolution and confocal immunofluorescence microscopy using an anMan-specific monoclonal antibody in non-growing, ascorbate-treated, and growing, untreated, wild-type mouse embryonic fibroblasts and hypoxia-exposed Alzheimer mouse Tg2576 fibroblasts and human U87 glioblastoma cells. In all cells, nuclear HS-anMan targeted a limited number of sites of variable size where it colocalized with DNA and nucleolin, an established marker for nucleoli. HS-anMan also colocalized with ethynyl uridine-tagged nascent RNA and two acetylated forms of histone H3. Acute hypoxia increased the formation of HS-anMan in both Tg2576 and U87 cells. A portion of HS-anMan colocalized with nucleolin at small discrete sites, while most of the nucleolin and nascent RNA was dispersed. In U87 cells, HS-anMan, nucleolin and nascent RNA reassembled after prolonged hypoxia. Nucleolar HS may modulate synthesis and/or release of rRNA.
  •  
24.
  • Cheng, Fang, et al. (author)
  • Potentiation of naphthoxyloside cytotoxicity on human tumor cells by difluoromethylornithine and spermine-NONOate.
  • 2009
  • In: Cancer Letters. - : Elsevier BV. - 1872-7980 .- 0304-3835. ; 273, s. 148-154
  • Journal article (peer-reviewed)abstract
    • Here we demonstrate a synergistic and tumor selective cytotoxic effect by combined treatment with naphthoxylosides, polyamine synthesis inhibitor, and polyamine based nitric oxide (NO) donor, using in vitro human tumor models. We have earlier reported that heparan sulfate priming naphthoxyloside, 2-(6-hydroxynaphthyl)-O-beta-d-xylopyranoside, which inhibits growth of human tumor cells in vitro and in vivo models, undergoes NO dependent cleavage and accumulates in the nuclei of tumor cells. Polyamine depletion using alpha-difluoromethylornithine (DFMO) increases both the number of NO sensitive sites in heparan sulfate and uptake of the polyamine based NO donor, spermineNONOate, thereby enhancing formation of growth-inhibitory NO induced heparan sulfate products with specific cytotoxic effect on tumor cells. We also show that peracetylation of xylosides doubles the antiproliferative effect towards human cancer cells by making these compounds more permeable to the cells.
  •  
25.
  • Cheng, Fang, et al. (author)
  • Proinflammatory cytokines induce accumulation of glypican-1-derived heparan sulfate and the C-terminal fragment of β-cleaved APP in autophagosomes of dividing neuronal cells
  • 2020
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423. ; 30:8, s. 539-549
  • Journal article (peer-reviewed)abstract
    • Proinflammatory cytokines stimulate expression of β-secretase, which increases processing of amyloid precursor protein (APP), ultimately leading to the deposition of amyloid beta (Aβ). The N-terminal domain of β-cleaved APP supports Cu/NO-dependent release of heparan sulfate (HS) from the glypican-1 (Gpc-1) proteoglycan. HS is an inhibitor of β-secretase, thereby constituting a regulatory, negative feedback loop. Here, we have investigated the effect of the proinflammatory cytokines TNF-α, IL-1β and IL-6 on the interplay between APP processing and release of HS from Gpc-1 in neuronal cells. We have used deconvolution immunofluorescence microscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and a panel of monoclonal/polyclonal antibodies recognizing the released HS, the N-terminus of Aβ, Aβ, the C-terminus of APP and the autophagosome marker LC3 as well as the chemical lysosome marker LysoTrackerRed (LTR). We repeatedly found that N2a neuroblastoma cells and human neural stem cells grown in the presence of the cytokines developed large cytoplasmic clusters, which stained positive for HS, the N-terminus of Aβ, Aβ, the C-terminus of APP, LC3 and LTR, indicating accumulation of HS and APP/APP degradation products in enlarged autophagosomes/lysosomes. The SDS-PAGE of immunoisolates obtained from TNF-α-treated N2a cells by using anti-C-terminus of APP revealed the presence of SDS-stable complexes between HS and the C-terminal fragment of β-cleaved APP (βCTF) migrating in the range 10-18 kDa. Clustered accumulation of βCTF disappeared when HS release was prevented and slightly enhanced when HS release was increased. Hence, when proinflammatory cytokines induce increased processing of APP, inhibition of β-secretase by HS is insufficient, which may lead to the impaired autophagosomal degradation.
  •  
26.
  • Cheng, Fang, et al. (author)
  • Rapid nuclear transit and impaired degradation of amyloid beta and glypican-1-derived heparan sulfate in Tg2576 mouse fibroblasts.
  • 2015
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 25:5, s. 548-556
  • Journal article (peer-reviewed)abstract
    • Anhydromannose (anMan)-containing heparan sulfate (HS) derived from S-nitrosylated glypican-1 is generated in endosomes by an endogenously or ascorbate induced S-nitrosothiol-catalyzed reaction. Expression and processing of amyloid precursor protein (APP) is required to initiate formation and endosome-to-nucleus translocation of anMan-containing HS in wild-type mouse embryonic fibroblasts (WT MEF). HS is then transported to autophagosomes and finally degraded in lysosomes. To investigate how APP-derived amyloid beta peptide (Aβ) affects intracellular trafficking of HS we have studied nuclear transit as well as autophagosome/lysosome targeting and degradation in Tg2576 MEF which produce increased amounts of Aβ. Deconvolution immunofluorescence microscopy with an anMan-specific monoclonal antibody showed anMan-staining in the nuclei of Tg2576 MEF after 5 min of ascorbate treatment and after 15 min in WT MEF. There was also greater nuclear accumulation of HS in Tg2576 MEF as determined by (35)S-sulfate labeling experiments. Tg2576 MEF was less sensitive to inhibition of NO production and copper-chelation than WT MEF. By using APP- and Aβ-recognizing antibodies we observed nuclear translocation of Aβ peptide in Tg2576 MEF but not in WT MEF. HS remained in the nucleus of WT MEF for at least 8 h and was then transported to autophagosomes. By 8 h HS had disappeared from the nuclei of Tg2576 MEF but colocalized poorly with the autophagosome marker LC3. Aβ also disappeared rapidly from the nuclei of Tg2576 MEF. Initially it appeared in acidic vesicles and later it accumulated extracellularly. Thus, in Tg2576 MEF there is nuclear accumulation as well as secretion of Aβ and impaired degradation of HS.
  •  
27.
  • Cheng, Fang, et al. (author)
  • Reversal of apolipoprotein E4-dependent or chemical-induced accumulation of APP degradation products by vitamin C-induced release of heparan sulfate from glypican-1
  • 2021
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423. ; 31:7, s. 800-811
  • Journal article (peer-reviewed)abstract
    • The Apolipoprotein E4 (ApoE4) genotype is the most influential risk factor for sporadic Alzheimer's disease. It appears to be associated with retarded endosome-to-autophagosome trafficking. The amyloid precursor protein (APP) and the heparan sulfate (HS)-containing proteoglycan glypican-1 (Gpc-1) are both processed in endosomes, and mutually regulated by the APP degradation products and the released HS. We have investigated APP and Gpc-1 processing in ApoE3 and ApoE4 expressing human fibroblasts, in human neural stem cells (NSC) exposed to the cholesterol transport inhibitor U18666A and in induced neurons obtained by reprogramming of ApoE fibroblasts (ApoE-iN). We have used immunofluorescence microscopy, flow cytometry, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis western blotting with antibodies recognizing the released HS, APP, amyloid β(Aβ), late endosomes (Rab7), autophagosomes (LC3) and neurons (Tuj1). We found that the capacity to release HS was not fully utilized in ApoE4 expressing fibroblasts and that HS-Aβ complexes accumulated in the nuclei. In ApoE3 fibroblasts, the β-cleaved APP C-terminal fragment (β-CTF) and Aβ were primarily present in late endosomes and autophagosomes. When HS release from Gpc-1 was enhanced by ascorbate in ApoE4/4 fibroblasts, there was efficient transfer of Aβ and HS from the nuclei to autophagosomes. In U18666A-treated NSC as well as in ApoE4/4-iN we repeatedly found accumulation of APP degradation products (β-CTF/Aβ). This was reversed by subsequent exposure to ascorbate or dehydroascorbic acid.
  •  
28.
  • Cheng, Fang, et al. (author)
  • Suppression of amyloid beta a11-immunoreactivity by vitamin C: possible role of heparan sulfate oligosaccharides derived from glypican-1 by ascorbate-induced, no-catalyzed degradation.
  • 2011
  • In: Journal of Biological Chemistry. - 1083-351X. ; 286:31, s. 27559-27572
  • Journal article (peer-reviewed)abstract
    • Amyloid beta is generated from the copper- and heparan sulfate (HS)-binding amyloid precursor protein (APP) by proteolytic processing. APP supports S-nitrosylation of the HS-proteoglycan glypican-1 (Gpc-1). In the presence of ascorbate there is NO-catalyzed release of anhydromannose (anMan)-containing oligosaccharides from Gpc-1-SNO. We have investigated whether these oligosaccharides interact with amyolid beta during APP processing and plaque formation. anMan-Immunoreactivity was detected in amyloid plaques of Alzheimer (AD) and APP transgenic (Tg2576) mouse brains by immunofluorescence microscopy. APP/APP degradation products detected by antibodies to the C-terminus of APP, but not amyolid beta oligomers detected by the anti-amyloid beta A11 antibody, colocalized with anMan-immunoreactivity in Tg2576 fibroblasts. A 50-55-kDa anionic, SDS-stable, anMan- and amyloid beta-immunoreactive species was obtained from Tg2576 fibroblasts using immunoprecipitation with anti-APP (C-terminal). anMan-Containing HS oligo- and disaccharide preparations modulated or suppressed A11-immunoreactivity and oligomerization of amyloid beta 42 peptide in an in vitro assay. A11 immunoreactivity increased in Tg2576 fibroblasts when Gpc-1 autoprocessing was inhibited by U18666A, and decreased when Gpc-1 autoprocessing was stimulated by ascorbate. Neither overexpression of Gpc-1 in Tg2576 fibroblasts nor addition of copper ion and NO-donor to hippocampal slices from 3xTg-AD mice affected A11 immunoreactivity levels. However, A11 immunoreactivity was greatly suppressed by the subsequent addition of ascorbate. We speculate that temporary interaction between the amyolid beta domain and small, anMan-containing oligosaccharides may preclude formation of toxic amyloid beta oligomers. A portion of the oligosaccharides co-secrete with the amyloid beta peptides and are deposited in plaques. These results support the notion that inadequate supply of vitamin C could contribute to late onset AD in humans.
  •  
29.
  • Cheng, Fang, et al. (author)
  • Suppression of glypican-1 autodegradation by NO-deprivation correlates with nuclear accumulation of amyloid beta in normal fibroblasts.
  • 2015
  • In: Glycoconjugate Journal. - : Springer Science and Business Media LLC. - 1573-4986 .- 0282-0080. ; 32:9, s. 675-684
  • Journal article (peer-reviewed)abstract
    • Heparan sulfate (HS)-containing, S-nitrosylated (SNO) glypican-1 (Gpc-1) releases anhydromannose-containing HS (anMan-HS) by SNO-catalyzed autodegradation in endosomes. Transport of anMan-HS to the nucleus requires processing of the amyloid precursor protein (APP) to amyloid beta peptides (Aβ). To further examine the relationship between APP and Gpc-1 processing in normal fibroblasts we have suppressed Gpc-1 autodegradation by aminoguanidine inhibition of NO synthesis and prevented lysosomal degradation of anMan-HS by using chloroquine. Deconvolution immunofluorescence microscopy and SDS-PAGE using anMan- and APP/Aβ-specific antibodies and markers for nuclei and autophagosomes were used to identify subcellular localization of Aβ and its oligomeric state. Wild-type mouse embryonic fibroblasts (WT MEF) grown during NO-deprivation accumulated 95-98 % of Aβ as oligomers in the nucleus. WT MEF treated with chloroquine accumulated both anMan-HS and Aβ, first in the nucleus then in autophagosomes. Maximal nuclear anMan-HS and Aβ accumulation was obtained after 4 and 7 h of growth, respectively. Both yielded similar banding patterns on SDS-PAGE which were also similar to the Aβ oligomers obtained after NO-deprivation. Nuclear Aβ accumulation was marginally increased (from 54 to 58 %) by suppression of both release and degradation of anMan-HS. Nuclear exit of Aβ, accumulated during growth in aminoguanidine, was enhanced by ascorbate-induced reactivation of anMan-HS production. Transgenic Alzheimer disease mouse (Tg2576) MEF, which produces excess amount of Aβ was used for comparison. Overall, nuclear Aβ exit and lysosomal degradation was compromised by inhibition of the autophagosome-lysosome pathway in both WT and Tg2576 MEF, while only WT MEF was sensitive to suppression of Gpc-1 autodegradation.
  •  
30.
  • Cheng, Fang, et al. (author)
  • The cyanobacterial neurotoxin β-N-methylamino-L-alanine prevents addition of heparan sulfate to glypican-1 and increases processing of amyloid precursor protein in dividing neuronal cells
  • 2019
  • In: Experimental Cell Research. - : Elsevier BV. - 0014-4827. ; 379:2, s. 172-181
  • Journal article (peer-reviewed)abstract
    • The neurotoxin β-N-methylamino-L-alanine replaces L-serine in proteins and produces Alzheimer-like pathology. In proteoglycans, e.g. glypican-1, this should preclude substitution with heparan sulfate chains. Reduced release of heparan sulfate should increase β-secretase activity and processing of amyloid precursor protein. Cultured cells were treated with β-N-methylamino-L-alanine during the growth-phase and the effect on heparan sulfate substitution and amyloid precursor protein processing was evaluated using antibodies specific for heparan sulfate, the N- and C-termini of the C-terminal fragment of β-cleaved amyloid precursor protein, and amyloid beta followed by immunofluorescence microscopy, flow cytometry or SDS-PAGE. Mouse fibroblasts, N2a neuroblastoma cells and human neural stem cells released less heparan sulfate when grown in the presence of β-N-methylamino-L-alanine. Cells expressing a recombinant, anchor-less glypican-1 secreted heparan sulfate-deficient glypican-1. There was increased processing of amyloid precursor protein in N2a cells when grown in the presence of the neurotoxin. The degradation products accumulated in cytoplasmic clusters. Secretion of amyloid beta increased approx. 3-fold. Human neural stem cells also developed cytoplasmic clusters containing degradation products of amyloid precursor protein. When non-dividing mouse N2a cells or cortical neurons were exposed to β-N-methylamino-L-alanine there was no effect on heparan sulfate substitution in glypican-1 or on amyloid precursor protein processing.
  •  
31.
  • Chérouvrier Hansson, Victor, et al. (author)
  • Dichotomous Effects of Glypican-4 on Cancer Progression and Its Crosstalk with Oncogenes
  • 2024
  • In: International Journal of Molecular Sciences. - 1661-6596. ; 25:7
  • Journal article (peer-reviewed)abstract
    • Glypicans are linked to various aspects of neoplastic behavior, and their therapeutic value has been proposed in different cancers. Here, we have systematically assessed the impact of GPC4 on cancer progression through functional genomics and transcriptomic analyses across a broad range of cancers. Survival analysis using TCGA cancer patient data reveals divergent effects of GPC4 expression across various cancer types, revealing elevated GPC4 expression levels to be associated with both poor and favorable prognoses in a cancer-dependent manner. Detailed investigation of the role of GPC4 in glioblastoma and non-small cell lung adenocarcinoma by genetic perturbation studies displays opposing effects on these cancers, where the knockout of GPC4 with CRISPR/Cas9 attenuated proliferation of glioblastoma and augmented proliferation of lung adenocarcinoma cells and the overexpression of GPC4 exhibited a significant and opposite effect. Further, the overexpression of GPC4 in GPC4-knocked-down glioblastoma cells restored the proliferation, indicating its mitogenic effect in this cancer type. Additionally, a survival analysis of TCGA patient data substantiated these findings, revealing an association between elevated levels of GPC4 and a poor prognosis in glioblastoma, while indicating a favorable outcome in lung carcinoma patients. Finally, through transcriptomic analysis, we attempted to assign mechanisms of action to GPC4, as we find it implicated in cell cycle control and survival core pathways. The analysis revealed upregulation of oncogenes, including FGF5, TGF-β superfamily members, and ITGA-5 in glioblastoma, which were downregulated in lung adenocarcinoma patients. Our findings illuminate the pleiotropic effect of GPC4 in cancer, underscoring its potential as a putative prognostic biomarker and indicating its therapeutic implications in a cancer type dependent manner.
  •  
32.
  • Ding, Kan, et al. (author)
  • Copper-dependent autocleavage of glypican-1heparan sulfate by nitric oxide derived fromintrinsic nitrosothiols.
  • 2002
  • In: Journal of Biological Chemistry. - 1083-351X. ; 277:36, s. 33353-33360
  • Journal article (peer-reviewed)abstract
    • Cell-surface heparan sulfate proteoglycans facilitate uptake of growth-promoting polyamines [ [Belting, M., Borsig, L., Fuster, M.M., Brown, J.R., Persson, L., Fransson,L.-. and Esko, J.D. (2002) Proc. Natl. Acad. Sci. U.S.A., 99, 371-376] ]. Increased polyamine uptake correlates with an increased number of positively charged N-unsubstituted glucosamine units in the otherwise polyanionic heparan sulfate chains of glypican-1. During intracellular recycling of glypican-1 there is an NO-dependent deaminative cleavage of heparan sulfate at these glucosamine units, which would eliminate the positive charges [ [Ding, K., Sandgren, S., Mani, K., Belting, M. and Fransson, L.-. (2001) J. Biol. Chem., 276, 46779-46791] ]. Here, using both biochemical and microscopic techniques, we have identified and isolated S-nitrosylated forms of glypican-1 as well as low-charged glypican-1 glycoforms containing heparan sulfate chains rich in N-unsubstituted glucosamines. The latter were converted to high-charged species upon treatment of cells with 1 mM L-ascorbate, which releases NO from nitrosothiols, resulting in deaminative cleavage of heparan sulfate at the N-unsubstituted glucosamines. S-nitrosylation and subsequent deaminative cleavage were abrogated by inhibition of a Cu 2+ /Cu + -redox cycle. Under cell-free conditions, purified, S-nitrosylated glypican-1 was able to autocleave its heparan sulfate chains when NO-release was triggered by L-ascorbate. The heparan sulfate fragments generated in cells during this auto-catalytic process contained terminal anhydromannose residues. We conclude that the core protein of glypican-1 can slowly accumulate NO as nitrosothiols while Cu 2+ is reduced to Cu +. Subsequent release of NO results in efficient deaminative cleavage of the heparan sulfate chains attached to the same core protein while Cu + is oxidized to Cu 2+.
  •  
33.
  • Ding, Kan, et al. (author)
  • Modulations of glypican-1 heparan sulfate structure by inhibition of endogenous polyamine synthesis. Mapping of spermine-binding sites and heparanase, heparin lyase, and nitric oxide/nitrite cleavage sites
  • 2001
  • In: Journal of Biological Chemistry. - 1083-351X. ; 276:50, s. 46779-46791
  • Journal article (peer-reviewed)abstract
    • Cell surface heparan sulfate proteoglycans facilitate uptake of growth-promoting polyamines (Belting, M., Persson, S., and Fransson, L.-A. (1999) Biochem. J. 338, 317-323; Belting, M., Borsig, L., Fuster, M. M., Brown, J. R., Persson, L., Fransson, L.-A., and Esko, J. D. (2001) Proc. Natl. Acad. Sci. U. S. A., in press). Here, we have analyzed the effect of polyamine deprivation on the structure and polyamine affinity of the heparan sulfate chains in various glypican-1 glycoforms synthesized by a transformed cell line (ECV 304). Heparan sulfate chains of glypican-1 were either cleaved with heparanase at sites embracing the highly modified regions or with nitrite at N-unsubstituted glucosamine residues. The products were separated and further degraded by heparin lyase to identify sulfated iduronic acid. Polyamine affinity was assessed by chromatography on agarose substituted with the polyamine spermine. In heparan sulfate made by cells with undisturbed endogenous polyamine synthesis, free amino groups were restricted to the unmodified, unsulfated segments, especially near the core protein. Spermine high affinity binding sites were located to the modified and highly sulfated segments that were released by heparanase. In cells with up-regulated polyamine uptake, heparan sulfate contained an increased number of clustered N-unsubstituted glucosamines and sulfated iduronic acid residues. This resulted in a greater number of NO/nitrite-sensitive cleavage sites near the potential spermine-binding sites. Endogenous degradation by heparanase and NO-derived nitrite in polyamine-deprived cells generated a separate pool of heparan sulfate oligosaccharides with an exceptionally high affinity for spermine. Spermine uptake in polyamine-deprived cells was reduced when NO/nitrite-generated degradation of heparan sulfate was inhibited. The results suggest a functional interplay between glypican recycling, NO/nitrite-generated heparan sulfate degradation, and polyamine uptake.
  •  
34.
  • Ding, Kan, et al. (author)
  • N-unsubstituted glucosamine in heparan sulfate of recycling glypican-1 from suramin-treated and nitrite-deprived endothelial cells. mapping of nitric oxide/nitrite-susceptible glucosamine residues to clustered sites near the core protein
  • 2001
  • In: Journal of Biological Chemistry. - 1083-351X. ; 276:6, s. 3885-3894
  • Journal article (peer-reviewed)abstract
    • We have analyzed the content of N-unsubstituted glucosamine in heparan sulfate from glypican-1 synthesized by endothelial cells during inhibition of (a) intracellular progression by brefeldin A, (b) heparan sulfate degradation by suramin, and/or (c) endogenous nitrite formation. Glypican-1 from brefeldin A-treated cells carried heparan sulfate chains that were extensively degraded by nitrous acid at pH 3.9, indicating the presence of glucosamines with free amino groups. Chains with such residues were rare in glypican-1 isolated from unperturbed cells and from cells treated with suramin and, surprisingly, when nitrite-deprived. However, when nitrite-deprived cells were simultaneously treated with suramin, such glucosamine residues were more prevalent. To locate these residues, chains were first cleaved at linkages to sulfated l-iduronic acid by heparin lyase and released fragments were separated from core protein carrying heparan sulfate stubs. These stubs were then cleaved off at sites linking N-substituted glucosamines to d-glucuronic acid. These fragments were extensively degraded by nitrous acid at pH 3.9. When purified proteoglycan isolated from brefeldin A-treated cells was incubated with intact cells, endoheparanase-catalyzed degradation generated a core protein with heparan sulfate stubs that were similarly sensitive to nitrous acid. We conclude that there is a concentration of N-unsubstituted glucosamines to the reducing side of the endoheparanase cleavage site in the transition region between unmodified and modified chain segments near the linkage region to the protein. Both sites as well as the heparin lyase-sensitive sites seem to be in close proximity to one another.
  •  
35.
  • Fransson, Lars-Åke, et al. (author)
  • Novel aspects of glypican glycobiology.
  • 2004
  • In: Cellular and Molecular Life Sciences. - : Springer Science and Business Media LLC. - 1420-9071 .- 1420-682X. ; 61:9, s. 1016-1024
  • Research review (peer-reviewed)abstract
    • Mutations in glypican genes cause dysmorphic and overgrowth syndromes in men and mice, abnormal development in flies and worms, and defective gastrulation in zebrafish and ascidians. All glypican core proteins share a characteristic pattern of 14 conserved cysteine residues. Upstream from the C-terminal membrane anchorage are 3–4 heparan sulfate attachment sites. Cysteines in glypican-1 can become nitrosylated by nitric oxide in a copper-dependent reaction. When glypican-1 is exposed to ascorbate, nitric oxide is released and participates in deaminative cleavage of heparan sulfate at sites where the glucosamines have a free amino group. This process takes place while glypican-1 recycles via a nonclassical, caveolin-1-associated route. Glypicans are involved in growth factor signalling and transport, e.g. of polyamines. Cargo can be unloaded from heparan sulfate by nitric oxide-dependent degradation. How glypican and its degradation products and the cargo exit from the recycling route is an enigma.
  •  
36.
  • Fransson, Lars-Åke, et al. (author)
  • Novel aspects of vitamin C: how important is glypican-1 recycling?
  • 2007
  • In: Trends in Molecular Medicine. - : Elsevier BV. - 1471-4914. ; 13:4, s. 143-149
  • Research review (peer-reviewed)abstract
    • The reduced form of vitamin C, ascorbic acid, is well known for its function as an antioxidant and as a protective agent against scurvy. However, many recent studies indicate other functions for vitamin C in mammalian cells. Novel findings provide possible explanations for observed beneficial effects of a high intake of vitamin C on cell growth, gene transcription, host resistance to infection, uptake of polyamines and clearance of misfolded proteins. Vitamin C exerts its effects indirectly via hypoxia-inducible factor, nitric oxide synthase and the heparan sulfate proteoglycan glypican-1, which is deglycanated in a vitamin C- and copper-dependent reaction.
  •  
37.
  • Jacobsson, Mårten, et al. (author)
  • Effects of oxygen-sulfur substitution on glycosaminoglycan-priming naphthoxylosides.
  • 2007
  • In: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896. ; 15:15, s. 5283-5299
  • Journal article (peer-reviewed)abstract
    • Three series of sulfur-containing analogs to the selectively antiproliferative 2-(6-hydroxynaphthyl) β-d-xylopyranoside were synthesized and their biological properties investigated. A short, general route to hydroxynaphthyl disulfides from dihydroxynaphthalenes was developed to utilize the disulfide bond as a sulfur-selective protecting group to enable the orthogonal protection of hydroxyls and thiols. The results indicate that hydrophobic, uncharged oxygen–sulfur substituted naphthoxylosides are taken up by cells and initiate priming of GAG chains to a greater extent compared to the oxygen analogs. No correlation between priming ability and antiproliferative activity was observed.
  •  
38.
  • Jacobsson, Mårten, et al. (author)
  • Selective antiproliferative activity of hydroxynaphthyl-beta-D-xylosides
  • 2006
  • In: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 1520-4804 .- 0022-2623. ; 49:6, s. 1932-1938
  • Journal article (peer-reviewed)abstract
    • The antiproliferative activity of the 14 isomeric monoxylosylated dihydroxynaphthalenes has been tested in vitro toward normal HFL-1 and 3T3 A31 cells as well as transformed T24 and 3T3 SV40 cells. The antiproliferative effect toward HFL-1 cells was correlated with the polarity of the compounds. However, in the case of transformed T24 cells, some compounds showed a clearly different behavior resulting in a selective antiproliferative effect. No such correlation was found for normal 3T3 A31 or virus transformed 3T3 SV40 cells, nor for the free aglycon. These results suggest that the antiproliferative activity shown by naphthoxylosides is diverse in different cell lines and dependent on the nature of the aglycon. The anti proliferative effect of 2- (6-hydroxynaphthyl)-beta-D-xylopyranoside, in contrast to inactive 2-naphthyl-beta-D-xylopyranoside, on T24 cells was accompanied by increased apoptosis as indicated by a TUNEL assay.
  •  
39.
  • Jacobsson, Mårten, et al. (author)
  • Xylose as a carrier for boron containing compounds
  • 2008
  • In: Bioorganic & Medicinal Chemistry Letters. - : Elsevier BV. - 0960-894X .- 1464-3405. ; 18:7, s. 2451-2454
  • Journal article (peer-reviewed)abstract
    • A xylosylated carborane was synthesized by standard carbohydrate methodology and tested on normal HFL-1 cells as well as transformed T24 cells. The xylosylated carborane initiated glycosaminoglycan (GAG) synthesis in both cell lines and treatment with the carborane gave a pronounced translocation of proteoglycans to the nuclei of T24 cells. However, most of the boron-containing compounds were secreted to the medium. We conclude that xylosides carrying carboranes are not suitable for boron neutron capture therapy (BNCT) for T24 cells. However, the uptake of boron-containing xyloside, the GAG priming capacity, and the nuclear translocation of glypican-1 make this xyloside a candidate for further investigation for selectivity toward other tumor cell lines.
  •  
40.
  • Johnsson, Richard, et al. (author)
  • Evaluation of fluorescently labeled xylopyranosides as probes for proteoglycan biosynthesis
  • 2007
  • In: Bioorganic & Medicinal Chemistry Letters. - : Elsevier BV. - 0960-894X. ; 17:8, s. 2338-2341
  • Journal article (peer-reviewed)abstract
    • A new fluorescent analog to the antiproliferative 2-(6-hydroxynaphthyl)-beta-D-xylopyranoside has been synthesized and tested on a T24 cell line. The new analog was efficiently uptaken by the T24 cells but did not initiate priming of GAG chains. The results are similar to other fluorescently labeled analogs and we propose that these compounds are too large and unpolar to efficiently function as GAG-primers. (c) 2007 Elsevier Ltd. All rights reserved.
  •  
41.
  • Johnsson, Richard, et al. (author)
  • Regioselective reductive openings of acetals; Mechanistic details and synthesis of fluorescently labeled compounds
  • 2006
  • In: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 1520-6904 .- 0022-3263. ; 71:9, s. 3444-3451
  • Journal article (peer-reviewed)abstract
    • Regioselective reductive openings of mixed phenolic-benzylic acetals, using BH3 center dot NMe3 center dot AlCl3, was investigated, and a mechanism where the outcome is directed by the electrostatic potential of the two oxygen atoms is presented. The regioselective acetal opening was used in the synthesis of a fluorescently labeled analogue to antiproliferative xylosides. The fluorescently labeled xyloside was tested for uptake, anti proliferative activity, and glycosaminoglycan priming in different cell lines. The xyloside was taken up by all cell lines but did not initiate glycosaminoglycan biosynthesis.
  •  
42.
  • Johnsson, Richard, et al. (author)
  • Synthesis and biology of bis-xylosylated dihydroxynaphthalenes.
  • 2007
  • In: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896. ; 15:8, s. 2868-2877
  • Journal article (peer-reviewed)abstract
    • The 10 analogous bis-xylosylated dihydroxynaphthalenes have been synthesized and their chemical and biological properties investigated. The yield of the xylosylation reactions can be correlated to the electrostatic potential, and thus to the nucleophilicity, for the oxygen atoms of the dihydroxynaphthalenes. The bis-xylosylated compounds were more stable compared to the mono-xylosylated ones. They initiate priming of glycosaminoglycan chains to less extent but the priming proceeds in two directions. Contrary to the mono-xylosylated analogs, the tested compounds did not show any antiproliferative properties.
  •  
43.
  • Löfgren, Kajsa, et al. (author)
  • Involvement of glypican-1 autoprocessing in scrapie infection
  • 2008
  • In: European Journal of Neuroscience. - : Wiley. - 1460-9568 .- 0953-816X. ; 28:5, s. 964-972
  • Journal article (peer-reviewed)abstract
    • The copper-binding cellular prion protein (PrPC) and the heparan sulphate (HS)-containing proteoglycan glypican-1 (Gpc-1) can both be attached to lipid rafts via their glycosylphosphatidylinositol anchors, and copper ions stimulate their cointernalization from the cell surface to endosomes. The prion protein controls cointernalization and delivers copper necessary for S-nitrosylation of conserved cysteines in the Gpc-1 core protein. Later, during recycling through endosomal compartments, nitric oxide can be released from the S-nitroso groups and catalyses deaminative degradation and release of the HS substituents. Here, by using confocal immunofluorescence microscopy, we show that normal PrPC and Gpc-1 colocalize inside GT1-1 cells. However, in scrapie-infected cells (ScGT1-1), Gpc-1 protein remained at the cell surface separate from the cellular prion protein. Scrapie infection stimulated Gpc-1 autoprocessing and the generated HS degradation products colocalized with intracellular aggregates of the disease-related scrapie prion protein isoform (PrPSc). Coimmunoprecipitation experiments demonstrated an association between Gpc-1 and PrPC in uninfected cells, and between HS degradation products and PrPSc in infected cells. Silencing of Gpc-1 expression or prevention of Gpc-1 autoprocessing elevated the levels of intracellular PrPSc aggregates in infected cells. These results suggest a role for Gpc-1 autoprocessing in the clearance of PrPSc from infected cells.
  •  
44.
  • Malmberg, Jesper, et al. (author)
  • Synthesis of aromatic C-xylosides by position inversion of glucose
  • 2006
  • In: Bioorganic & Medicinal Chemistry. - : Elsevier BV. - 0968-0896. ; 14:19, s. 6659-6665
  • Journal article (peer-reviewed)abstract
    • Two formally C-xylosylated analogs to 2-naphthyl beta-D-xylopyranoside, which is known to initiate priming of glucosaminoglycan chains, were synthesized by a position inversion of glucose (i.e., position I becomes position 5). The D-C-xyloside showed priming, while the L-C-xyloside did not initiate priming. (c) 2006 Elsevier Ltd. All rights reserved.
  •  
45.
  • Mani, Katrin, et al. (author)
  • Constitutive and vitamin C-induced, NO-catalyzed release of heparan sulfate from recycling glypican-1 in late endosomes.
  • 2006
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 16:12, s. 1251-1261
  • Journal article (peer-reviewed)abstract
    • The recycling heparan sulfate (HS)-containing proteoglycan glypican-1 (Gpc-1) is processed by nitric oxide (NO)-catalyzed deaminative cleavage of its HS chains at N-unsubstituted glucosamines. This generates anhydromannose (anMan)-containing HS degradation products that can be detected by a specific antibody. Here we have attempted to identify the intracellular compartments where these products are formed. The anMan-positive degradation products generated constitutively in human bladder carcinoma cell line (T24) or fibroblasts appeared neither in caveolin-1-associated vesicles nor in lysosomes. In Niemann-Pick C-1 (NPC-1) fibroblasts, where deaminative degradation is abrogated, formation of anMan-positive products can be restored by ascorbate. These products colocalized with Rab7, a marker for late endosomes. When NO-catalyzed degradation of HS was depressed in mouse neuroblastoma cell line (N2a) by using 3-beta[2(diethylamino) ethoxy]androst-5-en-17-one (U18666A), both ascorbate and dehydroascorbic acid restored formation of anMan-positive products that colocalized with Rab7. In T24 cells, constitutively generated anMan-positive products colocalized with both Rab7 and Rab9, whereas Gpc-1 colocalized with Rab9, a marker for transporting endosomes. Inhibition of endosomal acidification, which blocks transfer from early (Rab5) to late (Rab7) endosomes, abrogated deaminative degradation of HS. This could also be overcome by the addition of ascorbate, which induced formation of anMan-positive degradation products that colocalized with Rab7. After (35)S-sulfate labeling, similar degradation products were recovered in Rab7-positive vesicles. We conclude that NO-catalyzed degradation of HS may begin in early endosomes but is mainly taking place in late endosomes.
  •  
46.
  • Mani, Katrin, et al. (author)
  • Defective NO-dependent, deaminative cleavage of glypican-1 heparan sulfate in Niemann-Pick C1 fibroblasts.
  • 2006
  • In: Glycobiology. - : Oxford University Press (OUP). - 1460-2423 .- 0959-6658. ; 16:8, s. 711-718
  • Journal article (peer-reviewed)abstract
    • Exit of recycling cholesterol from late endosomes is defective in Niemann-Pick C1 (NPC1) and Niemann-Pick C2 (NPC2) diseases. The traffic route of the recycling proteoglycan glypican-1 (Gpc-1) may also involve late endosomes and could thus be affected in these diseases. During recycling through intracellular compartments, the heparan sulfate (HS) side chains of Gpc-1 are deaminatively degraded by nitric oxide (NO) derived from preformed S-nitroso groups in the core protein. We have now investigated whether this NO-dependent Gpc-1 autoprocessing is active in fibroblasts from NPC1 disease. The results showed that Gpc-1 autoprocessing was defective in these cells and, furthermore, greatly depressed in normal fibroblasts treated with U18666A (3-beta-[2-(diethylamino)ethoxy]androst-5-en-17-one), a compound widely used to induce cholesterol accumulation. In both cases, autoprocessing was partially restored by treatment with ascorbate which induced NO release, resulting in deaminative cleavage of HS. However, when NO-dependent Gpc-1 autoprocessing is depressed and heparanase-catalyzed degradation of HS remains active, a truncated Gpc-1 with shorter HS chains would prevail, resulting in fewer NO-sensitive sites/proteoglycan. Therefore, addition of ascorbate to cells with depressed autoprocessing resulted in nitration of tyrosines. Nitration was diminished when heparanase was inhibited with suramin or when Gpc-1 expression was silenced by RNAi. Gpc-1 misprocessing in NPC1 cells could thus contribute to neurodegeneration mediated by reactive nitrogen species.
  •  
47.
  • Mani, Katrin, et al. (author)
  • Heparan sulfate degradation products can associate with oxidized proteins and proteasomes.
  • 2007
  • In: Journal of Biological Chemistry. - 1083-351X. ; 282:30, s. 21934-21944
  • Journal article (peer-reviewed)abstract
    • The S-nitrosylated proteoglycan glypican-1 recycles via endosomes where its heparan sulfate chains are degraded into anhydromannose-containing saccharides by NO-catalyzed deaminative cleavage. Because heparan sulfate chains can be associated with intracellular protein aggregates, glypican-1 autoprocessing may be involved in the clearance of misfolded recycling proteins. Here we have arrested and then reactivated NO-catalyzed cleavage in the absence or presence of proteasome inhibitors and analyzed the products present in endosomes or co-precipitating with proteasomes using metabolic radiolabeling and immunomagnet isolation as well as by confocal immunofluorescence microscopy. Upon reactivation of deaminative cleavage in T24 carcinoma cells, [S-35] sulfate-labeled degradation products appeared in Rab7-positive vesicles and co-precipitated with a 20 S proteasome subunit. Simultaneous inhibition of proteasome activity resulted in a sustained accumulation of degradation products. We also demonstrated that the anhydromannose-containing heparan sulfate degradation products are detected by a hydrazide-based method that also identifies oxidized, i.e. carbonylated, proteins that are normally degraded in proteasomes. Upon inhibition of proteasome activity, pronounced colocalization between carbonyl-staining, anhydro-mannosecontaining degradation products, and proteasomes was observed in both T24 carcinoma and N2a neuroblastoma cells. The deaminatively generated products that co-precipitated with the proteasomal subunit contained heparan sulfate but were larger than heparan sulfate oligosaccharides and resistant to both acid and alkali. However, proteolytic degradation released heparan sulfate oligosaccharides. In Niemann-Pick C-1 fibroblasts, where deaminative degradation of heparan sulfate is defective, carbonylated proteins were abundant. Moreover, when glypican-1 expression was silenced in normal fibroblasts, the level of carbonylated proteins increased raising the possibility that deaminative heparan sulfate degradation is involved in the clearance of misfolded proteins.
  •  
48.
  • Mani, Katrin, et al. (author)
  • Involvement of GPI-linked ceruloplasmin in the Cu/Zn-NO-dependent degradation of glypican-1 heparan sulfate in Rat C6 glioma cells.
  • 2004
  • In: Journal of Biological Chemistry. - 1083-351X. ; 279:13, s. 12918-12923
  • Journal article (peer-reviewed)abstract
    • The core protein of glypican-1, a glycosylphosphatidylinositol-linked heparan sulfate proteoglycan, can bind Cu(II) or Zn(II) ions and undergo S-nitrosylation in the presence of nitric oxide. Cu(II)-to-Cu(I)-reduction supports extensive and permanent nitrosothiol formation, whereas Zn(II) ions appear to support a more limited, possibly transient one. Ascorbate induces release of nitric oxide, which catalyzes deaminative degradation of the heparan sulfate chains on the same core protein. Although free Zn(II) ions support a more limited degradation, Cu(II) ions support a more extensive self-pruning process. Here, we have investigated processing of glypican-1 in rat C6 glioma cells and the possible participation of the copper-containing glycosylphosphatidylinositol-linked splice variant of ceruloplasmin in nitrosothiol formation. Confocal microscopy demonstrated colocalization of glypican-1 and ceruloplasmin in endosomal compartments. Ascorbate induced extensive, Zn(II)-supported heparan sulfate degradation, which could be demonstrated using a specific zinc probe. RNA interference silencing of ceruloplasmin expression reduced the extent of Zn(II)-supported degradation. In cell-free experiments, the presence of free Zn(II) ions prevented free Cu(II) ion from binding to glypican-1 and precluded extensive heparan sulfate autodegradation. However, in the presence of Cu(II)-loaded ceruloplasmin, heparan sulfate in Zn(II)-loaded glypican-1 underwent extensive, ascorbate-induced degradation. We propose that the Cu(II)-to-Cu(I)-reduction that is required for S-nitrosylation of glypican-1 can take place on ceruloplasmin and thereby ensure extensive glypican-1 processing in the presence of free Zn(II) ions.
  •  
49.
  • Mani, Katrin (author)
  • Involvement of Heparan Sulphate Biosynthesis and Turnover in Cell Proliferation. A Novel Role for Nitric Oxide in Recycling of Heparan Sulphate Proteoglycans.
  • 2001
  • Doctoral thesis (other academic/artistic)abstract
    • The present investigation focuses on the role of HS metabolism in cell proliferation. The effect of the HS priming ß-D-xyloside, 2-(6-hydroxynaphthyl)-O-ß-D-xylopyranoside (Xyl-2-Nap-6-OH) on the proliferation of normal and transformed cells was studied. Xyl-2-Nap-6-OH inhibited growth of transformed cells to a significantly greater extent than normal cells. The growth inhibition exerted by the xyloside was believed to be due to its ability to prime GAG synthesis since the non-priming L-isomer did not possess any antiproliferative activity. The molecular structure of the aglycone and its ability to prime HS were other features assumed to be of importance for its antiproliferative activity. Recycling of HSPG may be a vehicle for endo/exocytosis of HS-binding growth factors and polyamines and thereby regulating cell proliferation. HSPG metabolism/recycling was therefore extensively studied in transformed endothelial cells. The major focus was on the role of NO-derived nitrite in the turnover of HSPG. As N-unsubstituted GlcN in HS chains are potential sites for NO-generated cleavage, the content and location of such residues was investigated. Transformed endothelial cells expressed a HSPG with a core protein of 60-70 kDa, which was recognised by a polyclonal antiserum raised against recombinant glypican-1 protein. In unperturbed cells, most of the radiolabelled glypican-1 carried truncated HS chains accompanied by HS oligosaccharides. Treatment with brefeldin A, which inhibits transport from the ER to the Golgi and also exit from the TGN and/or endocytosis in polarised cells, resulted in accumulation of glypican PG with full-size side chains while oligosaccharides disappeared. Treatment with suramin, an inhibitor of endoheparanase, led to partial inhibition of degradation of HS. Glypican-1 glycoforms in brefeldin A-treated cells contained long HS chains with GlcNH2 residues in multiple places, whereas unperturbed cells, suramin-treated cells, and nitrite-deprived cells contained short HS chains with only a few GlcNH2 residues. The number of GlcNH2 residues increased by combined suramin treatment and nitrite deprivation. This suggested that GlcNH2 residues and endoheparanase cleavage sites were closely located in HS chains. Pulse-chase studies clearly indicated that suramin arrested chains were the precursor of large-size PGs in the absence of de novo glypican-1 core protein synthesis. Recycling of suramin-arrested chains back to brefeldin A-arrested large PGs was precluded by nitrite deprivation. Formation of brefeldin A-arrested large glypican PGs was restored when NO-donor was supplied to nitrite-deprived cells. Taken together our data suggest a recycling of glypican-1 in transformed endothelial cells. During recycling, there is endoglycosidic cleavage of HS at or near GlcNH2 residues, and removal of these short nonreducing terminal GlcNH2 containing saccharides by NO derived nitrite would provide fresh acceptor-sites for HS chain extension. In order to assess the relationship between HS priming and antiproliferative activity of naphthol-containing ß-D-xylosides, cell proliferation assays and GAG priming studies were performed in the presence of nitrite depriving drugs. Different xylosides were synthesised and tested for growth inhibition and priming of HS synthesis. The selective growth-inhibitory effect of Xyl-2-Nap-6-OH appeared to be quite specific for this compound. Xylosides without the 6-hydroxyl, with an O-methylated 6-hydroxyl, with a free hydroxyl in a different position, or with non-fused aromatic rings were not antiproliferative. All of the tested naphthol-based xylosides were capable of priming HS synthesis. Inhibition of degradation by suramin or nitrite-deprivation resulted in increased intracellular accumulation of HS chains. Interestingly, nitrite-deprivation abrogated the growth inhibitory effect of Xyl-2-Nap-6-OH. We propose that Xyl-2-Nap-6-OH initiates synthesis of HS chains with occasional N-unsubstituted GlcN residues and that these chains can be taken up by the cells and degraded to bioactive compounds in the presence of nitrite.
  •  
50.
  • Mani, Katrin (author)
  • Isolation and Characterization of Heparan Sulfate Containing Amyloid Precursor Protein Degradation Products
  • 2022
  • In: Methods in Molecular Biology. - New York, NY : Springer US. - 1064-3745 .- 1940-6029. ; 2303, s. 279-288
  • Book chapter (peer-reviewed)abstract
    • Numerous studies indicate that heparan sulfate proteoglycans (HSPGs) participate in a network of complex molecular events involving amyloid precursor protein (APP) processing and formation, oligomerization, intracellular targeting, clearance, and propagation of amyloid β in Alzheimer’s disease (AD). A mutual functional interplay between recycling glypican-1 and APP processing has been demonstrated where the HS released from glypican-1 by a Cu/NO-ascorbate-dependent reaction forms a conjugate with APP degradation products and undergoes an endosome-nucleus-autophagosome co-trafficking. HS has been shown to display contradictory and dual effects in AD involving both prevention and promotion of amyloid β formation. It is therefore important to identify the source, detailed structural features as well as factors that favor formation of the neuroprotective forms of HS. Here, a method for isolation and identification of HS-containing APP degradation products has been described. The method is based on isolation of radiolabeled HS followed by identification of accompanying APP degradation products by SDS-PAGE and Western blotting.
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