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

Neurochem Int. 2008 May;52(6):1076-85. doi: 10.1016/j.neuint.2007.11.002. Epub 2007 Nov 21.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aminopyridines / pharmacology
  • Animals
  • Anti-Allergic Agents / pharmacology
  • Binding Sites / drug effects
  • Binding Sites / physiology
  • Binding, Competitive / drug effects
  • Binding, Competitive / physiology
  • Biological Assay
  • Calcium / metabolism*
  • Calcium / pharmacology
  • Calcium Signaling / drug effects
  • Calcium Signaling / physiology*
  • Copper / metabolism*
  • Copper / pharmacology
  • Dose-Response Relationship, Drug
  • Fibroblast Growth Factor 1 / metabolism*
  • Humans
  • Kinetics
  • Molecular Weight
  • Neurochemistry / instrumentation
  • Neurochemistry / methods
  • Quartz
  • S100 Proteins / metabolism*


  • Aminopyridines
  • Anti-Allergic Agents
  • S100 Proteins
  • S100A13 protein, human
  • Fibroblast Growth Factor 1
  • Quartz
  • Copper
  • amlexanox
  • Calcium