Phosphatidylinositol 4,5-bisphosphate increases Ca2+ affinity of synaptotagmin-1 by 40-fold

J Biol Chem. 2012 May 11;287(20):16447-53. doi: 10.1074/jbc.M112.343418. Epub 2012 Mar 23.


Synaptotagmin-1 is the main Ca(2+) sensor of neuronal exocytosis. It binds to both Ca(2+) and the anionic phospholipid phosphatidylinositol 4,5-bisphosphate (PIP(2)), but the precise cooperativity of this binding is still poorly understood. Here, we used microscale thermophoresis to quantify the cooperative binding of PIP(2) and Ca(2+) to synaptotagmin-1. We found that PIP(2) bound to the well conserved polybasic patch of the C2B domain with an apparent dissociation constant of ∼20 μM. PIP(2) binding reduced the apparent dissociation constant for Ca(2+) from ∼250 to <5 μM. Thus, our data show that PIP(2) makes synaptotagmin-1 >40-fold more sensitive to Ca(2+). This interplay between Ca(2+), synaptotagmin-1, and PIP(2) is crucial for neurotransmitter release.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / chemistry*
  • Calcium / metabolism
  • Neurotransmitter Agents / metabolism
  • Phosphatidylinositol 4,5-Diphosphate / chemistry*
  • Phosphatidylinositol 4,5-Diphosphate / metabolism
  • Protein Binding
  • Protein Structure, Tertiary
  • Rats
  • Synaptotagmin I / chemistry*
  • Synaptotagmin I / genetics
  • Synaptotagmin I / metabolism


  • Neurotransmitter Agents
  • Phosphatidylinositol 4,5-Diphosphate
  • Synaptotagmin I
  • Syt1 protein, rat
  • Calcium