The goal of this project is to identify factors that regulate neurotransmitter release kinetics. The motivation for this project is two-fold. First, slowed release of synaptic vesicles (SVs) prolongs post-synaptic currents, which can change post-synaptic excitability and action potential firing patterns. Thus, release kinetics has profoun effects on circuit development and cognition. Second, mutations linked to Autism alter post-synaptic response kinetics by various mechanisms. The SVs available for release comprise multiple functionally distinct pools, which fuse with different kinetics and release probabilities. Synchronous (or fast) release occurs over a few milliseconds while delayed (or slow) release occurs over 10-100 ms. The detailed mechanisms regulating release kinetics have not been determined. We propose to identify factors and mechanisms that tune release kinetics, using C. elegans as a model system. In preliminary studies, we identified three syntaxin-binding proteins that dictate release kinetics at neuromuscular junctions (NMJs). We showed that UNC-13L promotes fast release, UNC-13S promotes slow release, and Tomosyn (a third syntaxin-binding protein) inhibits slow release. Based on these preliminary results, we will determine how UNC-13L accelerates release, how the different UNC-13 proteins produce differences in spontaneous release, and how SVs are coupled to calcium channels. These studies should provide new insights into the biochemical mechanisms regulating release kinetics.
This proposal describes a coherent set of genetic, molecular, and biophysical experiments designed to identify factors that regulate the kinetics of neurotransmitter secretion at synapses. These experiments may uncover cellular mechanisms that contribute to the developmental and cognitive delays occurring in Autism and other psychiatric disorders.
