| 1. |
- Philipson, Ola, et al.
(författare)
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The Arctic amyloid-β precursor protein (AβPP) mutation results in distinct plaques and accumulation of N- and C-truncated Aβ
- 2012
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Ingår i: Neurobiology of Aging. - : Elsevier BV. - 0197-4580 .- 1558-1497. ; 33:5, s. 1010.e1-1010.e13
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic (p. E693G) mutation in the amyloid-β precursor protein (AβPP) facilitates amyloid-β (Aβ) protofibril formation and generates clinical symptoms of Alzheimer's disease (AD). Here, molecular details of Aβ in post mortem brain were investigated with biochemical and morphological techniques. The basic structure of Arctic plaques resembled cotton wool plaques. However, they appeared ring-formed with Aβ42-specific antibodies, but were actually targetoid, since the periphery and center of many parenchymal Aβ deposits stained differently with mid-domain, N- and C-terminal Aβ antibodies. Aβ fibrils were similar in shape, albeit shorter than in sporadic AD brain, when examined by electron microscopy. Aβwild-type and Aβarctic codeposited and parenchymal deposits were highly enriched in both N- and C-terminally truncated Aβ. In contrast, cerebral amyloid angiopathy (CAA) contained a substantial amount of Aβ1-40. The absence of plaques with cores of fibrillary Aβ might be due to the scarcity of full-length Aβ, although other mechanisms could be involved. Our findings are discussed in relation to mechanisms and relevance of amyloid formation and to the clinical features of AD.
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| 2. |
- Ekman, Sirkka-Liisa, et al.
(författare)
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Alzheimer
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Frykman, Susanne, et al.
(författare)
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Synaptic and Endosomal Localization of Active gamma-Secretase in Rat Brain
- 2010
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 5:1, s. e8948-
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundA key player in the development of Alzheimer's disease (AD) is the gamma-secretase complex consisting of at least four components: presenilin, nicastrin, Aph-1 and Pen-2. gamma-Secretase is crucial for the generation of the neurotoxic amyloid beta-peptide (A beta) but also takes part in the processing of many other substrates. In cell lines, active gamma-secretase has been found to localize primarily to the Golgi apparatus, endosomes and plasma membranes. However, no thorough studies have been performed to show the subcellular localization of the active gamma-secretase in the affected organ of AD, namely the brain.Principal FindingsWe show by subcellular fractionation of rat brain that high gamma-secretase activity, as assessed by production of A beta 40, is present in an endosome-and plasma membrane-enriched fraction of an iodixanol gradient. We also prepared crude synaptic vesicles as well as synaptic membranes and both fractions showed high A beta 40 production and contained high amounts of the gamma-secretase components. Further purification of the synaptic vesicles verified the presence of the gamma-secretase components in these compartments. The localization of an active gamma-secretase in synapses and endosomes was confirmed in rat brain sections and neuronal cultures by using a biotinylated gamma-secretase inhibitor together with confocal microscopy.SignificanceThe information about the subcellular localization of gamma-secretase in brain is important for the understanding of the molecular mechanisms of AD. Furthermore, the identified fractions can be used as sources for highly active gamma-secretase.
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| 4. |
- Keller, Lina, et al.
(författare)
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The PSEN1 I143T mutation in a Swedish family with Alzheimer's disease: clinical report and quantification of A beta in different brain regions
- 2010
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Ingår i: European Journal of Human Genetics. - London : Springer Science and Business Media LLC. - 1476-5438 .- 1018-4813. ; 18:11, s. 1202-1208
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Tidskriftsartikel (refereegranskat)abstract
- Early-onset dominantly inherited forms of Alzheimer's disease (AD) are rare, but studies of such cases have revealed important information about the disease mechanisms. Importantly, mutations in amyloid precursor protein (APP), presenilin 1 (PSEN1) and PSEN2, alter the APP processing and lead to an increased amyloid beta-peptide (A beta) 42/40 ratio. This, together with other studies on pathogenic mechanisms, show that A beta 42 is a major player in the etiology of AD. Here, we present a clinical and neuropathological description of a Swedish family with an I143T mutation in the PSEN1 gene, which gives rise to a severe form of AD. We also performed an extensive investigation on the concentration and distribution of A beta species of different lengths in six brain regions from two mutation carriers. Our study showed that A beta 42 and a longer peptide, A beta 43, were present both in plaque cores and in total amyloid preparations, and were each clearly more frequent than A beta 40 in all examined regions, as shown by both mass spectrometry and immunohistochemistry. European Journal of Human Genetics (2010) 18, 1202-1208; doi: 10.1038/ejhg.2010.107; published online 14 July 2010
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| 5. |
- Lindhagen Persson, Malin, 1982-
(författare)
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Targeting cytotoxic species in amyloid diseases
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Amyloid diseases are a world-wide problem causing great human suffer and large economical costs. Although amyloid deposits, a common denominator in all amyloid disorders, are detrimental to the surrounding tissue, there is a poor correlation between total amyloid burden and clinical symptoms. Soluble oligomers are much more potent to exert a tissue damaging effect. Alzheimer’s disease (AD) is strongly linked to self-assembly of the amyloid-β (Aβ) peptide. Antibodies selectively targeting cytotoxic Aβ-species are useful both for understanding oligomer formation and for their therapeutic abilities. We hypothesized that the effect of avidity would compensate for a low single site affinity and be enough to selectively target oligomers. To evaluate this hypothesis, we focused on the IgM isotype having ten antigen-binding sites. In accordance with the hypothesis, the IgM isotype effectively bound oligomeric Aβ also in presence of a vast excess of its monomeric counterpart, clearly illustrating the potentiating effect of avidity. As a continuation of this work, we have shown that the avidity effect from a bivalent binding is enough to induce oligomer specificity. This finding facilitates a direct application on the clinically more useful IgG isotype, where the binding properties now can be controlled in detail. The method is general and we have, using this technique, also designed oligomer specific antibodies targeting α-synuclein. Transthyretin (TTR) is an amyloidogenic protein involved in both hereditary and sporadic amyloidosis. The cytotoxicity of TTR is intriguing since studies have shown cytotoxic potential from oligomers, tetramers and even monomers. Elucidation of the molecular properties associated with TTR cytotoxicity is hence of interest. By preventing tetramer dissociation, TTR aggregation and TTR-induced cytotoxicity is abolished. Based on this rationale, a current therapeutic strategy is to stabilize the TTR tetramer with small molecules. The kinetic stability within the spectra of known TTR mutations spans more than three orders of magnitude. However, although the most stable mutants are inert, a poor correlation within the group of cytotoxic variants exists where the cytotoxic effect is not potentiated in proportion to their kinetic stability. Through analysis of a large spectra of TTR variants, our results indicate that TTR induced cytotoxicity requires an intermediate stability of the TTR molecule. The kinetic stability should be low enough to permit tetramer dissociation and the thermodynamic stability high enough to prevent instant aggregation and to allow formation of the cytotoxic fold.
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| 6. |
- Lu, Jun, et al.
(författare)
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Ebsulfur is a benzisothiazolone cytocidal inhibitor targeting the trypanothione reductase of Trypanosoma brucei
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:38, s. 27456-27468
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Tidskriftsartikel (refereegranskat)abstract
- Trypanosoma brucei is the causing agent of African trypanosomiasis. These parasites possess a unique thiol redox system required for DNA synthesis and defense against oxidative stress. It includes trypanothione and trypanothione reductase (TryR) instead of the thioredoxin and glutaredoxin systems of mammalian hosts. Here, we show that the benzisothiazolone compound ebsulfur (EbS), a sulfur analogue of ebselen, is a potent inhibitor of T. brucei growth with a favorable selectivity index over mammalian cells. EbS inhibited the TryR activity and decreased non-protein thiol levels in cultured parasites. The inhibition of TryR by EbS was irreversible and NADPH-dependent. EbS formed a complex with TryR and caused oxidation and inactivation of the enzyme. EbS was more toxic for T. brucei than for Trypanosoma cruzi, probably due to lower levels of TryR and trypanothione in T. brucei. Furthermore, inhibition of TryR produced high intracellular reactive oxygen species. Hydrogen peroxide, known to be constitutively high in T. brucei, enhanced the EbS inhibition of TryR. The elevation of reactive oxygen species production in parasites caused by EbS induced a programmed cell death. Soluble EbS analogues were synthesized and cured T. brucei brucei infection in mice when used together with nifurtimox. Altogether, EbS and EbS analogues disrupt the trypanothione system, hampering the defense against oxidative stress. Thus, EbS is a promising lead for development of drugs against African trypanosomiasis.
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| 7. |
- Lundgren, Jolanta L, et al.
(författare)
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Activity-independent release of the amyloid β-peptide from rat brain nerve terminals.
- 2014
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Ingår i: Neuroscience Letters. - : Elsevier BV. - 0304-3940 .- 1872-7972. ; 566:Mar 3, s. 125-130
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Tidskriftsartikel (refereegranskat)abstract
- Synaptic degeneration is one of the earliest hallmarks of Alzheimer disease. The molecular mechanism underlying this degeneration is not fully elucidated but one key player appears to be the synaptotoxic amyloid β-peptide (Aβ). The exact localization of the production of Aβ and the mechanisms whereby Aβ is released remain elusive. We have earlier shown that Aβ can be produced in crude synaptic vesicle fractions and it has been reported that increased synaptic activity results in increased secreted but decreased intracellular Aβ levels. Therefore, we considered whether Aβ could be produced in synaptic vesicles and/or released through the same mechanisms as neurotransmitters in synaptic vesicle exocytosis. Small amounts of Aβ were found to be produced in pure synaptic vesicle preparations. We also studied the release of glutamate and Aβ from rat cortical nerve terminals (synaptosomes). We found that large amounts of Aβ were secreted from non-stimulated synaptosomes, from which glutamate was not released. On the contrary, we could not detect any differences in Aβ release between non-stimulated synaptosomes and synaptosomes stimulated with KCl or 4-aminopyridine, whereas glutamate release was readily inducible in this system. To conclude, our results indicate that the major release mechanism of Aβ from isolated nerve terminals differs from the synaptic release of glutamate and that the activity-dependent increase of secreted Aβ, reported by several groups using intact cells, is likely dependent on post-synaptic events, trafficking and/or protein synthesis mechanisms.
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| 8. |
- Nahalkova, Jarmila, et al.
(författare)
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CD147, a gamma-secretase associated protein is upregulated in Alzheimer's disease brain and its cellular trafficking is affected by presenilin-2
- 2010
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Ingår i: Neurochemistry International. - : Elsevier BV. - 0197-0186 .- 1872-9754. ; 56:1, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- gamma-Secretase activity has been extensively investigated due to its role in Alzheimer's disease. Here, we studied the association of CD147, a transmembrane glycoprotein belonging to the immunoglobulin family, with gamma-secretase and its expression in Alzheimer's disease and control tissues. Subcellular fractionation of postmitochondrial supernatant from Fat brain on step iodixanol gradient in combination with co-immunoprecipitation using an anti-nicastrin antibody showed association of limited amount of CD147 to gamma-secretase. By immunoblotting of postnuclear pellets from Alzheimer's disease and control human brain tissues we showed that CD147 with molecular weight 75 kDa is upregulated in frontal cortex and thalamus of the Alzheimer's disease brains. Immunohistochemistry of brain tissues from Alzheimer's disease and control revealed specific Upregulation of CD147 in neurons, axons and capillaries of Alzheimer's disease frontal cortex and thalamus. The effect of presenilin-1 and -2, which are the catalytic subunits of gamma-secretase, on CD147 expression and subcellular localization was analyzed by confocal microscopy in combination with flow cytometry and showed that PS2 affected the subcellular localization of CD147 in Mouse embryonic fibroblast cells. We suggest that a small fraction of CD147 present in the brain is associated with the gamma-secretase, and can be involved in mechanisms dysregulated in Alzheimer's disease brain.
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| 9. |
- Sandebring, Anna, et al.
(författare)
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The Pathogenic A beta 43 Is Enriched in Familial and Sporadic Alzheimer Disease
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:2, s. e55847-
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Tidskriftsartikel (refereegranskat)abstract
- The amyloid-cascade hypothesis posits that the role of amyloid beta-peptide (A beta) in Alzheimer disease (AD) involves polymerization into structures that eventually are deposited as amyloid plaques. During this process, neurotoxic oligomers are formed that induce synaptic loss and neuronal death. Several different isoforms of A beta are produced, of which the 40 and 42 residue variants (A beta 40 and A beta 42) are the most common. A beta 42 has a strong tendency to form neurotoxic aggregates and is involved in AD pathogenesis. Longer A beta isoforms, like the less studied A beta 43, are gaining attention for their higher propensity to aggregate into neurotoxic oligomers. To further investigate A beta 43 in AD, we conducted a quantitative study on A beta 43 levels in human brain. We homogenized human brain tissue and prepared fractions of various solubility; tris buffered saline (TBS), sodium dodecyl sulfate (SDS) and formic acid (FA). Levels of A beta 43, as well as A beta 40 and A beta 42, were quantified using ELISA. We compared quantitative data showing A beta levels in occipital and frontal cortex from sporadic (SAD) and familial (FAD) AD cases, as well as non-demented (ND) controls. Results showed A beta 43 present in each fraction from the SAD and FAD cases, while its level was lower than the detection limit in the majority of the ND-cases. A beta 42 and A beta 43 were enriched in the less soluble fractions (SDS and FA) of SAD and FAD cases in both occipital and frontal cortex. Thus, although the total levels of A beta 43 in human brain are low compared to A beta 40 and A beta 42, we suggest that A beta 43 could initiate the formation of oligomers and amyloid plaques and thereby be crucial to AD pathogenesis.
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| 10. |
- Teranishi, Yasuhiro, et al.
(författare)
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Erlin-2 is associated with active γ-secretase in brain and affects amyloid β-peptide production
- 2012
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 424:3, s. 476-481
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Tidskriftsartikel (refereegranskat)abstract
- The transmembrane protease complex γ-secretase is responsible for the generation of the neurotoxic amyloid β-peptide (Aβ) from its precursor (APP). Aβ has a causative role in Alzheimer disease, and thus, γ-secretase is a therapeutic target. However, since there are more than 70 γ-secretase substrates besides APP, selective inhibition of APP processing is required. Recent data indicates the existence of several γ-secretase associated proteins (GSAPs) that affect the selection and processing of substrates. Here, we use a γ-secretase inhibitor for affinity purification of γ-secretase and associated proteins from microsomes and detergent resistant membranes (DRMs) prepared from rat or human brain. By tandem mass spectrometry we identified a novel brain GSAP; erlin-2. This protein was recently reported to reside in DRMs in the ER. A proximity ligation assay, as well as co-immunoprecipitation, confirmed the association of erlin-2 with γ-secretase. We found that a higher proportion of erlin-2 was associated with γ-secretase in DRMs than in soluble membranes. siRNA experiments indicated that reduced levels of erlin-2 resulted in a decreased Aβ production, whereas the effect on Notch processing was limited. In summary, we have found a novel brain GSAP, erlin-2, that resides in DRMs and affects Aβ production.
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| 11. |
- Wanngren, Johanna, et al.
(författare)
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Changed membrane integration and catalytic site conformation are two mechanisms behind the increased Aβ42/Aβ40 ratio by presenilin 1 familial Alzheimer-linked mutations.
- 2014
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Ingår i: FEBS Open Bio. - : Wiley. - 2211-5463. ; 4, s. 393-406
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Tidskriftsartikel (refereegranskat)abstract
- The enzyme complex γ-secretase generates amyloid β-peptide (Aβ), a 37-43-residue peptide associated with Alzheimer disease (AD). Mutations in presenilin 1 (PS1), the catalytical subunit of γ-secretase, result in familial AD (FAD). A unifying theme among FAD mutations is an alteration in the ratio Aβ species produced (the Aβ42/Aβ40 ratio), but the molecular mechanisms responsible remain elusive. In this report we have studied the impact of several different PS1 FAD mutations on the integration of selected PS1 transmembrane domains and on PS1 active site conformation, and whether any effects translate to a particular amyloid precursor protein (APP) processing phenotype. Most mutations studied caused an increase in the Aβ42/Aβ40 ratio, but via different mechanisms. The mutations that caused a particular large increase in the Aβ42/Aβ40 ratio did also display an impaired APP intracellular domain (AICD) formation and a lower total Aβ production. Interestingly, seven mutations close to the catalytic site caused a severely impaired integration of proximal transmembrane/hydrophobic sequences into the membrane. This structural defect did not correlate to a particular APP processing phenotype. Six selected FAD mutations, all of which exhibited different APP processing profiles and impact on PS1 transmembrane domain integration, were found to display an altered active site conformation. Combined, our data suggest that FAD mutations affect the PS1 structure and active site differently, resulting in several complex APP processing phenotypes, where the most aggressive mutations in terms of increased Aβ42/Aβ40 ratio are associated with a decrease in total γ-secretase activity.
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