Lars-Åke Fransson

Publications (4)11.98 Total impact

• Article: Non-conserved, S-nitrosylated cysteines in glypican-1 react with N-unsubstituted glucosamines in heparan sulfate and catalyze deaminative cleavage.

  Fang Cheng, Gabriel Svensson, Lars-Åke Fransson, Katrin Mani
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  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.
  Glycobiology 07/2012; · 3.58 Impact Factor
• Article: Suppression of amyloid beta A11 antibody immunoreactivity by vitamin C: possible role of heparan sulfate oligosaccharides derived from glypican-1 by ascorbate-induced, nitric oxide (NO)-catalyzed degradation.

  Fang Cheng, Roberto Cappai, Giuseppe D Ciccotosto, Gabriel Svensson, Gerd Multhaup, Lars-Åke Fransson, Katrin Mani
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  ABSTRACT: Amyloid β (Aβ) 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-nitrosothiol. We investigated whether these oligosaccharides interact with Aβ 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 Aβ oligomers detected by the anti-Aβ A11 antibody, colocalized with anMan immunoreactivity in Tg2576 fibroblasts. A 50-55-kDa anionic, sodium dodecyl sulfate-stable, anMan- and Aβ-immunoreactive species was obtained from Tg2576 fibroblasts using immunoprecipitation with anti-APP (C terminus). anMan-containing HS oligo- and disaccharide preparations modulated or suppressed A11 immunoreactivity and oligomerization of Aβ42 peptide in an in vitro assay. A11 immunoreactivity increased in Tg2576 fibroblasts when Gpc-1 autoprocessing was inhibited by 3-β[2(diethylamino)ethoxy]androst-5-en-17-one (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 Aβ domain and small, anMan-containing oligosaccharides may preclude formation of toxic Aβ oligomers. A portion of the oligosaccharides are co-secreted with the Aβ peptides and deposited in plaques. These results support the notion that an inadequate supply of vitamin C could contribute to late onset AD in humans.
  Journal of Biological Chemistry 06/2011; 286(31):27559-72. · 4.77 Impact Factor
• Article: Involvement of glypican-1 autoprocessing in scrapie infection.

  Kajsa Löfgren, Fang Cheng, Lars-Ake Fransson, Katarina Bedecs, Katrin Mani
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  ABSTRACT: The copper-binding cellular prion protein (PrP(C)) 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 PrP(C) 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 (PrP(Sc)). Coimmunoprecipitation experiments demonstrated an association between Gpc-1 and PrP(C) in uninfected cells, and between HS degradation products and PrP(Sc) in infected cells. Silencing of Gpc-1 expression or prevention of Gpc-1 autoprocessing elevated the levels of intracellular PrP(Sc) aggregates in infected cells. These results suggest a role for Gpc-1 autoprocessing in the clearance of PrP(Sc) from infected cells.
  European Journal of Neuroscience 09/2008; 28(5):964-72. · 3.63 Impact Factor
• Article: Defective NO-dependent, deaminative cleavage of glypican-1 heparan sulfate in Niemann-Pick C1 fibroblasts

  Katrin Mani, Fang Cheng, Lars-Åke Fransson
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  ABSTRACT: Exit of recycling cholesterol from late endosomes is defective in Niemann-Pick C1 and C2 diseases. The traffic route of the recycling proteoglycan glypican-1 may also involve late endosomes, and could thus be affected in these diseases. During recycling through intracellular compartments, the heparan sulfate side-chains of glypican-1 are deaminatively degraded by nitric oxide derived from preformed S-nitroso groups in the core protein. We have now investigated whether this nitric oxide-dependent glypican-1 autoprocessing is active in fibroblasts from Niemann-Pick C1 disease. The results showed that glypican-1 autoprocessing was defective in these cells and, furthermore, greatly depressed in normal fibroblasts treated with U18666A (3-β[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 nitric oxide release, resulting in deaminative cleavage of heparan sulfate. However, when nitric oxide-dependent glypican-1 autoprocessing is depressed and heparanase-catalyzed degradation of heparan sulfate remains active, a truncated glypican-1 with shorter heparan sulfate chains would prevail, resulting in fewer nitric oxide-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 glypican-1 expression was silenced by RNAi. Glypican-1 misprocessing in Niemann-Pick C1 cells could thus contribute to neurodegeneration mediated by reactive nitrogen species.