Munc13 C2B domain is an activity-dependent Ca2+ regulator of synaptic exocytosis

Nat Struct Mol Biol. 2010 Mar;17(3):280-8. doi: 10.1038/nsmb.1758. Epub 2010 Feb 14.


Munc13 is a multidomain protein present in presynaptic active zones that mediates the priming and plasticity of synaptic vesicle exocytosis, but the mechanisms involved remain unclear. Here we use biophysical, biochemical and electrophysiological approaches to show that the central C(2)B domain of Munc13 functions as a Ca(2+) regulator of short-term synaptic plasticity. The crystal structure of the C(2)B domain revealed an unusual Ca(2+)-binding site with an amphipathic alpha-helix. This configuration confers onto the C(2)B domain unique Ca(2+)-dependent phospholipid-binding properties that favor phosphatidylinositolphosphates. A mutation that inactivated Ca(2+)-dependent phospholipid binding to the C(2)B domain did not alter neurotransmitter release evoked by isolated action potentials, but it did depress release evoked by action-potential trains. In contrast, a mutation that increased Ca(2+)-dependent phosphatidylinositolbisphosphate binding to the C(2)B domain enhanced release evoked by isolated action potentials and by action-potential trains. Our data suggest that, during repeated action potentials, Ca(2+) and phosphatidylinositolphosphate binding to the Munc13 C(2)B domain potentiate synaptic vesicle exocytosis, thereby offsetting synaptic depression induced by vesicle depletion.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Calcium / metabolism*
  • Crystallography, X-Ray
  • Electrophysiology
  • Exocytosis / genetics
  • Exocytosis / physiology*
  • Magnetic Resonance Spectroscopy
  • Molecular Sequence Data
  • Nerve Tissue Proteins / chemistry*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Phospholipids
  • Protein Structure, Tertiary / genetics
  • Rats
  • Sequence Homology, Amino Acid
  • Spectrometry, Fluorescence
  • Synaptic Transmission / genetics
  • Synaptic Transmission / physiology*
  • Synaptic Vesicles / genetics
  • Synaptic Vesicles / metabolism*


  • Nerve Tissue Proteins
  • Phospholipids
  • Unc13a protein, rat
  • Calcium

Associated data

  • PDB/3KWT
  • PDB/3KWU