The C. elegans WASH complex supports epithelial polarity by promoting endosomal sorting of Cadherin

Epithelial polarity requires polarized distribution of the apical adhesion complex that connects cells through the Cadherin transmembrane protein. Cadherin is intimately linked to the actin cytoskeleton through alpha catenin, which directly binds F-actin to set up the apical actin belt. Branched actin is formed when the Arp2/3 complex is activated by Nucleation Promoting Factors. C. elegans has three Nucleation Promoting Factors, WASP, WAVE and WASH. Our studies showed that WAVE-dependent branched actin promotes apical transport of Cadherin, including apically-directed transport of RAB-11-enriched endosomes. However, the contribution of other Nucleation Promoting Factors to Cadherin polarity has not been examined. The C. elegans WASH complex is not well described. Here we characterize components of the WASH complex, and confirm that CO5G5.2, despite being highly divergent, is the functional FAM21 component in C. elegans. We show that the WASH complex is enriched at early and recycling endosomes in the adult intestine, where it supports retrograde Cadherin transport. Our findings demonstrate that individual branched actin regulators promote specific transport steps, and identify WASH function at RME-1/EHD-enriched endosomes as an important contributor to Cadherin polarity and cargo sorting in a mature epithelium.