For better or for worse: complexins regulate SNARE function and vesicle fusion

Traffic. 2008 Sep;9(9):1403-13. doi: 10.1111/j.1600-0854.2008.00758.x. Epub 2008 Apr 28.


In contrast to constitutive secretion, SNARE-mediated synaptic vesicle fusion is controlled by multiple regulatory proteins, which determine the Ca(2+) sensitivity of the vesicle fusion process and the speed of excitation-secretion coupling. Complexins are among the best characterized SNARE regulators known to date. They operate by binding to trimeric SNARE complexes consisting of the vesicle protein synaptobrevin and the plasma membrane proteins syntaxin and SNAP-25. The question as to whether complexins facilitate or inhibit SNARE-mediated fusion processes is currently a matter of significant controversy. This is mainly because of the fact that biochemical experiments in vitro and studies on vertebrate complexins in vivo have yielded apparently contradictory results. In this review, I provide a summary of available data on the role of complexins in SNARE-mediated vesicle fusion and attempt to define a model of complexin function that incorporates evidence for both facilitatory and inhibitory roles of complexins in SNARE-mediated fusion.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adaptor Proteins, Vesicular Transport
  • Animals
  • Humans
  • Membrane Fusion / physiology*
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism
  • Nerve Tissue Proteins / physiology*
  • Protein Binding
  • SNARE Proteins / metabolism
  • SNARE Proteins / physiology*
  • Synaptic Vesicles / metabolism
  • Synaptic Vesicles / physiology*


  • Adaptor Proteins, Vesicular Transport
  • Nerve Tissue Proteins
  • SNARE Proteins
  • complexin I
  • complexin II