The claudin-like molecule CLC-3 regulates cholinergic neurotransmission in <i>Caenorhabditis elegans</i>

Cell adhesion molecules (CAMs) play important roles in neurons, contributing to nervous system development, synapse formation and plasticity. A subset of CAMs, Claudins, known for their roles at tight junctions, remains underexplored in neurons. Recent studies in Caenorhabditis elegans have begun to reveal neuronal functions of claudin-like proteins. However, a systematic analysis of their neuronal expression has not been performed. We conducted a transcriptional reporter screen for claudin-like genes in C. elegans and identified several candidates showing neuronal expression, highlighting possible roles for claudins in the nervous system. One candidate, clc-3, showed robust expression in head, tail, and ventral cord neurons, with no detectable expression in non-neuronal tissues. Functional analyses of clc-3 mutants revealed increased body-bend amplitudes and elevated evoked postsynaptic currents at the cholinergic neuromuscular synapses. Imaging and molecular interaction studies demonstrated that CLC-3 likely interacts with the actin-binding protein NAB-1 to regulate cholinergic transmission. Our findings identify CLC-3 as a neuronally expressed claudin that regulates motor system output, likely through synaptic vesicle organization and illustrates how changes in synaptic function affect animal behavior.