| 1. |
- Nordström, Ulrika, et al.
(författare)
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Progressive nigrostriatal terminal dysfunction and degeneration in the engrailed1 heterozygous mouse model of Parkinson's disease.
- 2015
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Ingår i: Neurobiology of Disease. - : Elsevier BV. - 0969-9961. ; 73, s. 70-82
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Tidskriftsartikel (refereegranskat)abstract
- Current research on Parkinson's disease (PD) pathogenesis requires relevant animal models that mimic the gradual and progressive development of neuronal dysfunction and degeneration that characterizes the disease. Polymorphisms in engrailed 1 (En1), a homeobox transcription factor that is crucial for both the development and survival of mesencephalic dopaminergic neurons, are associated with sporadic PD. This suggests that En1 mutant mice might be a promising candidate PD model. Indeed, a mouse that lacks one En1 allele exhibits decreased mitochondrial complex I activity and progressive midbrain dopamine neuron degeneration in adulthood, both features associated with PD. We aimed to further characterize the disease-like phenotype of these En1(+/-) mice with a focus on early neurodegenerative changes that can be utilized to score efficacy of future disease modifying studies. We observed early terminal defects in the dopaminergic nigrostriatal pathway in En1(+/-) mice. Several weeks before a significant loss of dopaminergic neurons in the substantia nigra could be detected, we found that striatal terminals expressing high levels of dopaminergic neuron markers TH, VMAT2, and DAT were dystrophic and swollen. Using transmission electron microscopy, we identified electron dense bodies consistent with abnormal autophagic vacuoles in these terminal swellings. In line with these findings, we detected an up-regulation of the mTOR pathway, concurrent with a downregulation of the autophagic marker LC3B, in ventral midbrain and nigral dopaminergic neurons of the En1(+/-) mice. This supports the notion that autophagic protein degradation is reduced in the absence of one En1 allele. We imaged the nigrostriatal pathway using the CLARITY technique and observed many fragmented axons in the medial forebrain bundle of the En1(+/-) mice, consistent with axonal maintenance failure. Using in vivo electrochemistry, we found that nigrostriatal terminals in the dorsal striatum were severely deficient in dopamine release and reuptake. Our findings support a progressive retrograde degeneration of En1(+/-) nigrostriatal neurons, akin to what is suggested to occur in PD. We suggest that using the En1(+/-) mice as a model will provide further key insights into PD pathogenesis, and propose that axon terminal integrity and function can be utilized to estimate dopaminergic neuron health and efficacy of experimental PD therapies.
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| 2. |
- Escobar Galvis, Martha L., et al.
(författare)
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Heat stress response in pea involves interaction of mitochondrial nucleoside diphosphate kinase with a novel 86-kilodalton protein
- 2001
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Ingår i: Plant Physiology. - 1532-2548. ; 126:1, s. 69-77
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Tidskriftsartikel (refereegranskat)abstract
- In this work we have further characterized the first mitochondrial nucleoside diphosphate kinase (mtNDPK) isolated from plants. The mitochondrial isoform was found to be especially abundant in reproductive and young tissues. Expression of the pea (Pisum sativum L. cv Oregon sugarpod) mtNDPK was not affected by different stress conditions. However, the pea mtNDPK was found to interact with a novel 86-kD protein, which is de novo synthesized in pea leaves upon exposure to heat. Thus, we have evidence for the involvement of mtNDPK in mitochondrial heat response in pea in vivo. Studies on oligomerization revealed that mtNDPK was found in complexes of various sizes, corresponding to the sizes of e.g. hexamers, tetramers, and dimers, indicating flexibility in oligomerization. This flexibility, also found for other NDPK isoforms, has been correlated with the ability of this enzyme to interact with other proteins. We believe that the mtNDPK is involved in heat stress response in pea, possibly as a modulator of the 86-kD protein.
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| 3. |
- Escobar Galvis, Martha L
(författare)
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Signalling in plant mitochondria. Redox regulation of gene expression & characterisation of a pea nucleoside diphosphate kinase
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work contributes to our understanding of mitochondrial responses to changing environmental conditions in plants. The first part of this thesis is focused in the study of redox regulation of mitochondrial gene expression. By using inhibitors, the redox state of the components of the mitochondrial respiratory chain was selectively affected. Effects of the altered redox state of these components on mitochondrial translation were studied. This approach allowed the identification of the respiratory complex II as a key component of regulation of mitochondrial translation. Furthermore, results indicating that protein phosphorylation might be part of this regulatory system are also presented. The other aspect investigated in this work is the characterisation of a recently isolated mitochondrial protein, the pea mitochondrial nucleoside diphosphate kinase (pea mtNDPK). Cloning, expression studies, organellar targeting and phylogenetic analysis of this protein are described. Functional characterisation of the pea mtNDPK revealed a role in stress response. It was found, that the pea mtNDPK interacts with a novel 86 kDa protein, of which synthesis is up-regulated upon heat stress in vivo. The pea mtNDPK seems to have various oligomeric states, suggesting its interaction with different types of substrates. The data presented here indicate that the pea mtNDPK most likely is part of the plant mitochondrial response to heat stress, possibly acting as a modulator of the heat up-regulated 86 kDa protein.
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| 4. |
- Escobar Galvis, Martha L., et al.
(författare)
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Transgenic or tumor-induced expression of heparanase upregulates sulfation of heparan sulfate
- 2007
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Ingår i: Nature Chemical Biology. - : Springer Science and Business Media LLC. - 1552-4450 .- 1552-4469. ; 3:12, s. 773-778
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Tidskriftsartikel (refereegranskat)abstract
- Heparan sulfate proteoglycans (HSPGs) interact with numerous proteins of importance in animal development and homeostasis. Heparanase, which is expressed in normal tissues and upregulated in angiogenesis, cancer and inflammation, selectively cleaves β-glucuronidic linkages in HS chains. In a previous study, we transgenically overexpressed heparanase in mice to assess the overall effects of heparanase on HS metabolism. Metabolic labeling confirmed extensive fragmentation of HS in vivo. In the current study we found that in liver showing excessive heparanase overexpression, HSPG turnover is accelerated along with upregulation of HS N- and O-sulfation, thus yielding heparin-like chains without the domain structure typical of HS. Heparanase overexpression in other mouse organs and in human tumors correlated with increased 6-O-sulfation of HS, whereas the domain structure was conserved. The heavily sulfated HS fragments strongly promoted formation of ternary complexes with fibroblast growth factor 1 (FGF1) or FGF2 and FGF receptor 1. Heparanase thus contributes to regulation of HS biosynthesis in a way that may promote growth factor action in tumor angiogenesis and metastasis.
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| 5. |
- Gong, Feng, et al.
(författare)
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Processing of macromolecular heparin by heparanase
- 2003
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 278:37, s. 35152-35158
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Tidskriftsartikel (refereegranskat)abstract
- Heparanase is an endo-glucuronidase expressed in a variety of tissues and cells that selectively cleaves extracellular and cell-surface heparan sulfate. Here we propose that this enzyme is involved also in the processing of serglycin heparin proteoglycan in mouse mast cells. In this process, newly synthesized heparin chains (60-100 kDa) are degraded to fragments (10-20 kDa) similar in size to commercially available heparin (Jacobsson, K. G., and Lindahl, U. (1987) Biochem. J. 246, 409-415). A fraction of these fragments contains the specific pentasaccharide sequence required for high affinity binding to antithrombin implicated with anticoagulant activity. Rat skin heparin, which escapes processing in vivo, was used as a substrate in reaction with recombinant human heparanase. An incubation product of commercial heparin size retained the specific pentasaccharide sequence, although oligosaccharides (3-4 kDa) containing this sequence could be degraded by the same enzyme. Commercial heparin was found to be a powerful inhibitor (I50 approximately 20 nM expressed as disaccharide unit, approximately 0.7 nM polysaccharide) of heparanase action toward antithrombin-binding oligosaccharides. Cells derived from a serglycin-processing mouse mastocytoma expressed a protein highly similar to other mammalian heparanases. These findings strongly suggest that the intracellular processing of the heparin proteoglycan polysaccharide chains is catalyzed by heparanase, which primarily cleaves target structures distinct from the antithrombin-binding sequence.
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| 6. |
- Li, Jin-Ping, et al.
(författare)
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In vivo fragmentation of heparan sulfate by heparanase overexpression renders mice resistant to amyloid protein A amyloidosis
- 2005
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 102:18, s. 6473-7
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid diseases encompass >20 medical disorders that include amyloid protein A (AA) amyloidosis, Alzheimer's disease, and type 2 diabetes. A common feature of these conditions is the selective organ deposition of disease-specific fibrillar proteins, along with the sulfated glycosaminoglycan, heparan sulfate. We have generated transgenic mice that overexpress human heparanase and have tested their susceptibility to amyloid induction. Drastic shortening of heparan sulfate chains was observed in heparanase-overproducing organs, such as liver and kidney. These sites selectively escaped amyloid deposition on experimental induction of inflammation-associated AA amyloidosis, as verified by lack of material staining with Congo Red, as well as lack of associated polysaccharide, whereas the same tissues from control animals were heavily infiltrated with amyloid. By contrast, the spleens of transgenic mice that failed to significantly overexpress heparanase contained heparan sulfate chains similar in size to those of control spleen and remained susceptible to amyloid deposition. Our findings provide direct in vivo evidence that heparan sulfate is essential for the development of amyloid disease.
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