Calcium-Dependent Release of Peptides is Needed for Neurotransmission in Caenorhabditis elegans

Science Center, Bent Corridor

Neuromodulation is extremely important to nervous system function and adaptability. C. elegans have over 100 distinct neuropeptides, most of which have unknown function/s1. We are investigating the role of intestinal neuropeptides in C. elegans neuronal function. C. elegans intestinal calcium waves travel along the length of the intestine via gap junctional connections between cells2. Recent studies suggest that the intestinal calcium waves induce the release of a neuropeptide called NLP-40 that regulates the activity of a motor neuron involved in defecation3. NLP-40 may also modulate neurotransmission more broadly2,4. We are investigating the role of NLP-40 and the intestinal calcium wave in acetylcholinebased neurotransmission. We hypothesize that the intestinal calcium wave elicits the release of NLP-40 and other peptides that modulate acetylcholine-based neurotransmission. To address this hypothesis we compared the defects induced by loss of NLP-40, its receptor, and functional intestinal calcium waves. To cause abnormal intestinal calcium waves animals with a mutation in a gap junction protein called innexin-16 (inx-16) were used. This mutation dramatically alters the speed and directionality of the intestinal calcium wave, disrupts defecation, NLP-40 release, reproductive capacity and acetylcholine response. To determine if loss of NLP-40 is sufficient to explain inx-16 defects we have assayed the effects of losing functional NLP-40 or its receptor, AEX-2. If the intestinal calcium wave only releases NLP-40 then we expect all of the mutants’ defects to be comparable. If the gap junction mutant has more severe defects then NLP-40 release, this suggests that additional peptides are released from the intestine. In all of our assays genetically disrupting NLP-40, its receptor and intestinal gap junctions produced significant abnormalities compared to normal animals. The phenotype of the inx-16 mutants was significantly worse than NLP-40 and its receptor in most assays. Our results suggest that the intestinal calcium wave is responsible for the release of multiple neuropeptides that regulate several aspects of C. elegans physiology and function.