Synaptic Activity Regulates the Abundance and Binding of Complexin

Biophys J. 2015 Mar 24;108(6):1318-1329. doi: 10.1016/j.bpj.2014.12.057.

Abstract

Nervous system function relies on precise chemical communication between neurons at specialized junctions known as synapses. Complexin (CPX) is one of a small number of cytoplasmic proteins that are indispensable in controlling neurotransmitter release through SNARE and synaptic vesicle interactions. However, the mechanisms that recruit and stabilize CPX are poorly understood. The mobility of CPX tagged with photoactivatable green fluorescent protein (pGFP) was quantified in vivo using Caenorhabditis elegans. Although pGFP escaped the synapse within seconds, CPX-pGFP displayed both fast and slow decay components, requiring minutes for complete exchange of the synaptic pool. The longer synaptic residence time of CPX arose from both synaptic vesicle and SNARE interactions, and surprisingly, CPX mobility depended on synaptic activity. Moreover, mouse CPX-GFP reversibly dispersed out of hippocampal presynaptic terminals during stimulation, and blockade of vesicle fusion prevented CPX dispersion. Hence, synaptic CPX can rapidly redistribute and this exchange is influenced by neuronal activity, potentially contributing to use-dependent plasticity.

MeSH terms

  • Adaptor Proteins, Vesicular Transport / genetics
  • Adaptor Proteins, Vesicular Transport / metabolism*
  • Animals
  • Axons / physiology
  • CA1 Region, Hippocampal / physiology
  • CA3 Region, Hippocampal / physiology
  • Caenorhabditis elegans
  • Cells, Cultured
  • Exocytosis / physiology
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Mice
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Presynaptic Terminals / physiology
  • Rats, Sprague-Dawley
  • SNARE Proteins / metabolism
  • Synapses / physiology*
  • Synaptic Transmission / physiology
  • Synaptic Vesicles / physiology

Substances

  • Adaptor Proteins, Vesicular Transport
  • Nerve Tissue Proteins
  • SNARE Proteins
  • complexin I
  • Green Fluorescent Proteins