Presynaptic UNC-31 (CAPS) is required to activate the Gαs pathway of the Caenorhabditis elegans synaptic signaling network

Abstract

C. elegans mutants lacking the dense-core vesicle priming protein UNC-31 (CAPS) share highly similar phenotypes with mutants lacking a neuronal Gαs pathway, including strong paralysis despite exhibiting near normal levels of steady-state acetylcholine release as indicated by drug sensitivity assays. Our genetic analysis shows that UNC-31 and neuronal Gαs are different parts of the same pathway and that the UNC-31/Gαs pathway is functionally distinct from the presynaptic Gαq pathway with which it interacts. UNC-31 acts upstream of Gαs because mutations that activate the Gαs pathway confer similar levels of strongly hyperactive, coordinated locomotion in both unc-31 null and (1) backgrounds. Using cell-specific promoters, we show that both UNC-31 and the Gαs pathway function in cholinergic motor neurons to regulate locomotion rate. Using immunostaining we show that UNC-31 is often concentrated at or near active zones of cholinergic motor neuron synapses. Our data suggest that presynaptic UNC-31 activity, likely acting via dense-core vesicle exocytosis, is required to locally activate the neuronal Gαs pathway near synaptic active zones. Copyright © 2006 by the Genetics Society of America.