Clathrin adaptor AP-1 complex excludes multiple postsynaptic receptors from axons in C. elegans.

Neurons are highly polarized cells with morphologically and molecularly distinct axonal and dendritic compartments. It is not well understood how postsynaptic receptors are selectively enriched in dendrites in vivo. We investigated the molecular mechanisms of dendritically polarized localization of a glutamate receptor, an acetylcholine receptor, and a ROR-type receptor tyrosine kinase in the interneuron RIA in C. elegans. We found that the clathrin adaptor AP-1 complex mu1 subunit UNC-101 functions cell autonomously to maintain the correct localization of these receptors in a dynamin-dependent manner. In unc-101 mutants, instead of being dendritically enriched, all 3 receptors are evenly distributed in the axonal and dendritic compartments. Surprisingly, UNC-101 predominantly localizes to the axonal compartment, suggesting a possible transcytosis model for the dendritic targeting of neurotransmitter receptors.