Proteolysis of SNARE proteins alters facilitation and depression in a specific way.

The molecular mechanisms of short-term plasticity observed during synaptic transmission are unknown. To determine whether the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins play a role in short-term plasticity, Botulinum toxins A, E, and F, were used to disrupt SNARE protein function in cultured hippocampal neurons. Although low concentrations of all of the toxins significantly reduced evoked release, they differentially affected short-term plasticity as assessed by the paired-pulse ratio, regardless of the initial release probability and size of the readily releasable pool of the synapse. The toxin effects on the paired-pulse ratio resulted in different phenotypes dependent on the toxin cleavage site. Together, these data indicate proteolysis of SNARE proteins alters facilitation and depression in a specific way.