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Cheng F, Fransson LÅ, Mani K. Interplay between glypican-1, amyloid-β and tau phosphorylation in human neural stem cells. Neuroscience 2024; 553:121-127. [PMID: 38992568 DOI: 10.1016/j.neuroscience.2024.07.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2024] [Revised: 06/19/2024] [Accepted: 07/04/2024] [Indexed: 07/13/2024]
Abstract
INTRODUCTION Alzheimer's disease (AD) is characterized by accumulation of amyloid beta (Aβ) and hyperphosphorylated tau (Tau-P) in the brain. Aβ enhances the activity of kinases involved in the formation of Tau-P. Phosphorylation at Thr 181 determines the propagation of multiple tau phosphorylations. Aβ is derived from the amyloid precursor protein (APP). Cleavage of APP by β-secretase also initiates release of heparan sulfate (HS) from the proteoglycan glypican-1 (GPC1). OBJECTIVES In this study, we have explored possible connections between GPC1 expression, HS release, APP processing and Tau-P formation in human neural stem cells. METHODS GPC1 formation was suppressed by using CRISPR/Cas9 and increased by using a vector encoding GPC1. HS release from GPC1 was increased by growing cells in medium containing Arg and ascorbate. Effects were monitored by immunofluorescence microscopy and slot immunoblotting using antibodies/antisera recognizing Aβ, GPC1, HS released from GPC1, total Tau, and Tau phosphorylated at Thr-181, 217 or 231. The latter have been used as blood biomarkers for AD. RESULTS Suppression of GPC1 expression resulted in increased phosphorylation at Thr 181 and Thr 217. When GPC1 was overexpressed, phosphorylation at Thr 217 decreased. Stimulation of HS release from GPC1 diminished tau phosphorylation at all of the three Thr positions, while expression of GPC1 was unaffected. Simultaneous stimulation of HS release and APP processing by the cytokine TNF-α also suppressed tau phosphorylation. CONCLUSION The increased release of GPC1-derived HS may interfere with Aβ formation and/or Aβ interaction with tau.
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Affiliation(s)
- Fang Cheng
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Lars-Åke Fransson
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Katrin Mani
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden.
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Cheng F, Fransson LÅ, Mani K. Complex modulation of cytokine-induced α-synuclein aggregation by glypican-1-derived heparan sulfate in neural cells. Glycobiology 2021; 32:333-342. [PMID: 34939110 PMCID: PMC8970428 DOI: 10.1093/glycob/cwab126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 12/01/2021] [Accepted: 12/02/2021] [Indexed: 12/03/2022] Open
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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Affiliation(s)
- Fang Cheng
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Lars-Åke Fransson
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Katrin Mani
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
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Cheng F, Fransson LÅ, Mani K. Reversal of apolipoprotein E4-dependent or chemical-induced accumulation of APP degradation products by vitamin C-induced release of heparan sulfate from glypican-1. Glycobiology 2021; 31:800-811. [PMID: 33403386 DOI: 10.1093/glycob/cwaa120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 12/17/2020] [Accepted: 12/17/2020] [Indexed: 12/20/2022] Open
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 SDS-PAGE-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.
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Affiliation(s)
- Fang Cheng
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Lars-Åke Fransson
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Katrin Mani
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
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Cheng F, Fransson LÅ, Mani K. 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. Glycobiology 2020; 30:539-549. [PMID: 32039447 PMCID: PMC7372925 DOI: 10.1093/glycob/cwaa011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 01/12/2020] [Accepted: 01/30/2020] [Indexed: 12/17/2022] Open
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.
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Affiliation(s)
- Fang Cheng
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, 221 00 Lund, Sweden
| | - Lars-Åke Fransson
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, 221 00 Lund, Sweden
| | - Katrin Mani
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, 221 00 Lund, Sweden
- To whom correspondence should be addressed: Tel: +46-46-222-4044; e-mail:
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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. Exp Cell Res 2019; 379:172-181. [DOI: 10.1016/j.yexcr.2019.03.041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 03/27/2019] [Accepted: 03/30/2019] [Indexed: 12/20/2022]
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Du J, Liu S, Liang Q, Lin J, Jiang L, Chen F, Wei Z. Analysis of Heparan sulfate/heparin from Colla corii asini by liquid chromatography-electrospray ion trap mass spectrometry. Glycoconj J 2019; 36:211-218. [DOI: 10.1007/s10719-019-09868-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 03/14/2019] [Accepted: 03/26/2019] [Indexed: 11/29/2022]
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Young TR, Pukala TL, Cappai R, Wedd AG, Xiao Z. The Human Amyloid Precursor Protein Binds Copper Ions Dominated by a Picomolar-Affinity Site in the Helix-Rich E2 Domain. Biochemistry 2018; 57:4165-4176. [DOI: 10.1021/acs.biochem.8b00572] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Tessa R. Young
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Tara L. Pukala
- Discipline of Chemistry, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Roberto Cappai
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Anthony G. Wedd
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Zhiguang Xiao
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Victoria 3010, Australia
- Melbourne Dementia Research Centre, Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria 3052, Australia
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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. Exp Cell Res 2017; 360:171-179. [DOI: 10.1016/j.yexcr.2017.09.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 08/30/2017] [Accepted: 09/01/2017] [Indexed: 11/21/2022]
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Cheng F, Belting M, Fransson LÅ, Mani K. Nucleolin is a nuclear target of heparan sulfate derived from glypican-1. Exp Cell Res 2017; 354:31-39. [PMID: 28300561 DOI: 10.1016/j.yexcr.2017.03.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/09/2017] [Accepted: 03/10/2017] [Indexed: 12/11/2022]
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.
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Affiliation(s)
- Fang Cheng
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Mattias Belting
- Department of Clinical Sciences, Section of Oncology and Pathology, Lund University, Lund, Sweden
| | - Lars-Åke Fransson
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
| | - Katrin Mani
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden.
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Du JY, Chen LR, Liu S, Lin JH, Liang QT, Lyon M, Wei Z. Ion-pairing liquid chromatography with on-line electrospray ion trap mass spectrometry for the structural analysis of N-unsubstituted heparin/heparan sulfate. J Chromatogr B Analyt Technol Biomed Life Sci 2016; 1028:71-76. [DOI: 10.1016/j.jchromb.2016.06.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 06/02/2016] [Accepted: 06/03/2016] [Indexed: 11/30/2022]
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Cheng F, Bourseau-Guilmain E, Belting M, Fransson LÅ, Mani K. Hypoxia induces NO-dependent release of heparan sulfate in fibroblasts from the Alzheimer mouse Tg2576 by activation of nitrite reduction. Glycobiology 2016; 26:623-34. [DOI: 10.1093/glycob/cww007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 01/13/2016] [Indexed: 12/12/2022] Open
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Suppression of glypican-1 autodegradation by NO-deprivation correlates with nuclear accumulation of amyloid beta in normal fibroblasts. Glycoconj J 2015; 32:675-84. [DOI: 10.1007/s10719-015-9616-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Revised: 08/10/2015] [Accepted: 08/12/2015] [Indexed: 11/25/2022]
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Liang QT, Du JY, Fu Q, Lin JH, Wei Z. Preparation and characterization of heparin hexasaccharide library with N-unsubstituted glucosamine residues. Glycoconj J 2015; 32:643-53. [DOI: 10.1007/s10719-015-9612-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 07/15/2015] [Accepted: 07/24/2015] [Indexed: 11/27/2022]
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Liang QT, Xiao XM, Lin JH, Wei Z. A new sequencing approach for N-unsubstituted heparin/heparan sulfate oligosaccharides. Glycobiology 2015; 25:714-25. [DOI: 10.1093/glycob/cwv011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 02/07/2015] [Indexed: 01/28/2023] Open
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Cheng F, Cappai R, Lidfeldt J, Belting M, Fransson LÅ, Mani K. Amyloid precursor protein (APP)/APP-like protein 2 (APLP2) expression is required to initiate endosome-nucleus-autophagosome trafficking of glypican-1-derived heparan sulfate. J Biol Chem 2015; 289:20871-8. [PMID: 24898256 DOI: 10.1074/jbc.m114.552810] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Anhydromannose (anMan)-containing heparan sulfate (HS) derived from the proteoglycan glypican-1 is generated in endosomes by an endogenously or ascorbate-induced S-nitrosothiolcatalyzed reaction. Processing of the amyloid precursor protein (APP) and APP-like protein 2 (APLP2) by β- and γ-secretases into amyloid β(A) and Aβ-like peptides also takes place in these compartments. Moreover, anMan-containing HS suppresses the formation of toxic Aβ assemblies in vitro. We showed by using deconvolution immunofluorescence microscopy with an anMan-specific monoclonal antibody as well as (35)S labeling experiments 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 MEFs), Tg2576 MEFs, and N2a neuroblastoma cells but not in APP(-/-) and APLP2(-/-) MEFs. Transfection of APP(-/-) cells with a vector encoding APP restored nuclear import of anMan-containing HS. In WT MEFs 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 MEFs, 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 MEFs. 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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Cheng F, Fransson LÅ, Mani K. Rapid nuclear transit and impaired degradation of amyloid β and glypican-1-derived heparan sulfate in Tg2576 mouse fibroblasts. Glycobiology 2014; 25:548-56. [DOI: 10.1093/glycob/cwu185] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
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Cheng F, Ruscher K, Fransson LÅ, Mani K. Non-toxic amyloid beta formed in the presence of glypican-1 or its deaminatively generated heparan sulfate degradation products. Glycobiology 2013; 23:1510-9. [PMID: 24026238 DOI: 10.1093/glycob/cwt079] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The amyloid beta (Aβ) peptides (mainly Aβ40 and Aβ42), 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 Aβ 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 Aβ40 and Aβ42, as well as Aβ40/42 mixtures that were formed in the presence of immobilized Gpc-1 PG or immobilized HS oligosaccharides. Afterwards, Aβ 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 Aβ multimerization into oligomers as well as larger aggregates that were mostly A11 positive and showed toxic effects. However, non-toxic Aβ was formed in the presence of Gpc-1 PG or when anMan-containing HS degradation products were simultaneously generated. Both toxic and non-toxic Aβ 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 Aβ peptides.
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Affiliation(s)
- Fang Cheng
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group
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