title: Involvement of glycosylphosphatidylinositol-linked ceruloplasmin in the copper/zinc-nitric oxide-dependent degradation of glypican-1 heparan sulfate in rat C6 glioma cells.
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.
authors.affiliation: Department of Cell and Molecular Biology, Section for Cell and Matrix Biology, Lund University, Biomedical Center C13, SE-221 84 Lund, Sweden.
authors.forename: Katrin
authors.initials: K
authors.lastname: Mani
authors.forename: Fang
authors.initials: F
authors.lastname: Cheng
authors.forename: Birgitta
authors.initials: B
authors.lastname: Havsmark
authors.forename: Samuel
authors.initials: S
authors.lastname: David
authors.forename: Lars-Ake
authors.initials: LA
authors.lastname: Fransson
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000378:metabolism; D045744:Cell Line, Tumor; D002474:Cell-Free System; D002570:Ceruloplasmin / Q000737:chemistry* / Q000378:metabolism; D002845:Chromatography; D003300:Copper / Q000737:chemistry; D005910:Glioma / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000737:chemistry*; D019812:Heparan Sulfate Proteoglycans / Q000737:chemistry*; D006497:Heparan Sulfate / Q000737:chemistry*; D007477:Ions; D018613:Microscopy, Confocal; D008954:Models, Biological; D009569:Nitric Oxide / Q000737:chemistry; D009584:Nitrogen / Q000378:metabolism; D051381:Rats; D015032:Zinc / Q000737:chemistry
chemical_list: D001205:Ascorbic Acid; D002570:Ceruloplasmin; D003300:Copper; D017261:Glycosylphosphatidylinositols; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D007477:Ions; D009569:Nitric Oxide; D009584:Nitrogen; D015032:Zinc