title: Synergistic Ca2+ and Cu2+ requirements of the FGF1-S100A13 interaction measured by quartz crystal microbalance: an initial step in amlexanox-reversible non-classical release of FGF1.
abstract: It is known that fibroblast growth factor-1 (FGF1) lacking a conventional signal peptide sequence shows non-classical release independent of the endoplasmic reticulum-Golgi system. Recent studies reveal that FGF1 is co-released with S100A13, a Ca2+-binding protein that acts as an extracellular cargo molecule. Although both FGF1 and S100A13 are Cu2+-binding proteins, the role of Cu2+, as well as that of Ca2+, in non-classical release, remains to be clarified. In the present study we examined the requirements of both metal ions for the interaction between these two proteins. The addition of Ca2+ significantly increased the ka value, while decreasing the KD value, for the interaction between Strep-tagII-S100A13 and GST-FGF1; both values were obtained by use of a quartz crystal microbalance, a real-time mass-measuring device. The EC50 of Ca2+ to enhance the interaction was 10.11 microM. Although the addition of Cu2+ alone had no effect, it caused a marked potentiation of the Ca2+-enhanced interaction. The EC50 of Cu2+ for the potentiation was 50.45 nM. On the other hand, the EC50 of Ca2+ and the KD values were decreased from 11.69 to 2.07 microM and 0.75 to 0.38 x 10(-7)M, respectively, by the addition of 200 nM Cu2+. The Cu2+-induced potentiation of this interaction was abolished by amlexanox, which inhibits non-classical release of FGF1. All of these findings suggest that synergistic effects of Ca2+ and Cu2+ play a key role in the interaction between FGF1 and S100A13, which is the initial step in non-classical release of FGF1.
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: D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D018926:Anti-Allergic Agents / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D001681:Biological Assay; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D003300:Copper / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D016220:Fibroblast Growth Factor 1 / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008970:Molecular Weight; D009448:Neurochemistry / Q000295:instrumentation / Q000379:methods; D011791:Quartz; D009418:S100 Proteins / Q000378:metabolism*
chemical_list: D000631:Aminopyridines; D018926:Anti-Allergic Agents; D009418:S100 Proteins; C511523:S100A13 protein, human; D016220:Fibroblast Growth Factor 1; D011791:Quartz; D003300:Copper; C045742:amlexanox; D002118:Calcium