The Claudin-like protein HPO-30 is required to maintain LAChRs at the C. elegans neuromuscular junction

Communications across chemical synapses are primarily mediated by neurotransmitters and their postsynaptic receptors. There are diverse molecular systems to localize and regulate the receptors at the synapse. Here, we identify HPO-30, a member of the claudin superfamily of membrane proteins, as a positive regulator for synaptic localization of levamisole dependent acetylcholine receptors (LAChRs) at the Caenorhabditis elegans neuromuscular junction. The HPO-30 protein localizes at the NMJ and shows genetic and physical association with the LAChR subunits LEV-8, UNC-29 and UNC-38. Using genetic and electrophysiological assays in the hermaphrodite C. elegans we demonstrate that HPO-30 functions through the Neuroligin, NLG-1 at the NMJ to maintain postsynaptic LAChR levels at the synapse. Taken together, this work suggests a novel function for a tight junction protein in maintaining normal receptor levels at the NMJ. SIGNIFICANCE STATEMENT Claudins are a large superfamily of membrane proteins. Their role in maintaining the functional integrity of tight junctions has been widely explored. Our experiments suggest a critical role for the claudin-like protein, HPO-30 in maintaining synaptic LAChR levels. LAChRs contribute to less then twenty percent of the acetylcholine-mediated conductance in adult C. elegans , however, they play a significant functional role in worm locomotion. This study provides a new perspective in the study of LAChR physiology.