Calcium signaling and neuropeptide secretion in the expulsion step of the Caenorhabditis elegans defecation motor program (1129.6)

Abstract

A periodic posterior to anterior intestinal calcium wave initiates the defecation motor program of Caenorhabditis elegans (C. elegans). innexin‐16 (inx‐16) encodes an intestinal pannexin gap junction subunit. inx‐16 mutants have faulty calcium waves and mostly lack the expulsion step of the motor program. Our work investigates how these defective calcium waves result in loss of expulsion. The anterior‐ventral neuron L (AVL) and dorsal‐ventral neuron B (DVB) are responsible for expulsion through a two‐step signaling process. An intestinal neuropeptide‐like protein, NLP‐40, activates AVL and DVB which in turn release neurotransmitters to stimulate expulsion. NLP‐40 release likely depends on intestinal calcium flux, as vesicular localization of NLP‐40 requires synaptotagmin‐2.We propose that the expulsion defects in the inx‐16 mutant are due to improper NLP‐40 release. To establish if inx‐16’s AVL and DVB neurons are functional, we used optogenetic methods. Activation of a light‐gated ion channel channelrhodopsin‐2 (ChR2) in AVL and DVB of inx‐16 animals resulted in normal expulsion 90% of the time. This demonstrates that an inx‐16 animal’s AVL and DVB neurons are able to signal expulsion and supports our hypothesis that defects in inx‐16’s intestinal NLP‐40 release inhibit expulsion. Current work addresses whether NLP‐40 is properly synthesized and released.