Evolutionary conservation of complexins: from choanoflagellates to mice

EMBO Rep. 2015 Oct;16(10):1308-17. doi: 10.15252/embr.201540305. Epub 2015 Sep 3.


Complexins are synaptic SNARE complex-binding proteins that cooperate with synaptotagmins in activating Ca(2+)-stimulated, synaptotagmin-dependent synaptic vesicle exocytosis and in clamping spontaneous, synaptotagmin-independent synaptic vesicle exocytosis. Here, we show that complexin sequences are conserved in some non-metazoan unicellular organisms and in all metazoans, suggesting that complexins are a universal feature of metazoans that predate metazoan evolution. We show that complexin from Nematostella vectensis, a cnidarian sea anemone far separated from mammals in metazoan evolution, functionally replaces mouse complexins in activating Ca(2+)-triggered exocytosis, but is unable to clamp spontaneous exocytosis. Thus, the activating function of complexins is likely conserved throughout metazoan evolution.

Keywords: SNARE proteins; evolution; membrane fusion; synapse; synaptotagmin.

Publication types

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

MeSH terms

  • Adaptor Proteins, Vesicular Transport / chemistry*
  • Adaptor Proteins, Vesicular Transport / metabolism*
  • Amino Acid Sequence
  • Animals
  • Biological Evolution*
  • Calcium / metabolism
  • Choanoflagellata / chemistry
  • Choanoflagellata / genetics*
  • Conserved Sequence
  • Exocytosis
  • Mice
  • Nerve Tissue Proteins / chemistry*
  • Nerve Tissue Proteins / metabolism*
  • Phylogeny
  • Protein Binding / genetics*
  • Protein Structure, Secondary
  • SNARE Proteins
  • Synaptic Transmission
  • Synaptotagmins / genetics
  • Synaptotagmins / physiology


  • Adaptor Proteins, Vesicular Transport
  • Nerve Tissue Proteins
  • SNARE Proteins
  • Synaptotagmins
  • Calcium