title: Evidence for serum-deprivation-induced co-release of FGF-1 and S100A13 from astrocytes.
abstract: Since fibroblast growth factor (FGF)-1 lacks conventional amino-terminal signal peptide essential for endoplasmic reticulum (ER)-Golgi pathway, the mode of release of this polypeptide remains to be fully understood. We attempted to characterize the non-classical (non-vesicular) mode of FGF-1 release in the analyses using immunocytochemistry and immunoblot of conditioned medium (CM) from astrocytes. FGF-1 was completely released from astrocytes upon serum-deprivation stress in a Brefeldin A-insensitive manner. In the immunoprecipitation study using anti-FGF-1 IgG, S100A13 was identified to be the major protein co-eluted with FGF-1. The interaction between GST-FGF-1 and Strep-tag II-S100A13 was found to be Ca(2+)-sensitive, and to require the C-terminal 11 amino acid peptide sequence of S100A13. The overexpression of Delta88-98 mutant of S100A13 selectively inhibited the serum-deprivation stress-induced release of FGF-1, but not the release of S100A13 mutant from C6 glioma cells. However, amlexanox, anti-allergic drug whose target is S100A13, completely inhibited the stress-induced release of FGF-1 as well as S100A13. The stress-induced release of both proteins was also abolished by BAPTA-AM, an intracellular Ca(2+) chelating agent. The serum-deprivation caused Ca(2+) spikes in omega-conotoxin GVIA and thapsigargin-sensitive manner. All these results suggest that S100A13 is a cargo molecule for the serum-deprivation stress-induced non-classical release of FGF-1, and that its driving force of protein-protein interaction and release is possibly mediated by Ca(2+)-induced Ca(2+) release (CICR) coupled to N-type Ca(2+) channel activity.
authors.affiliation: Division of Molecular Pharmacology and Neuroscience, Nagasaki University Graduate School of Biomedical Sciences, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Matsunaga
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ueda
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D016220:Fibroblast Growth Factor 1 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D051381:Rats; D009418:S100 Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000172:deficiency
chemical_list: D016895:Culture Media, Serum-Free; D009418:S100 Proteins; D016220:Fibroblast Growth Factor 1; D020126:Brefeldin A; D012710:Serum Albumin, Bovine