Endocytic sorting and recycling require membrane phosphatidylserine asymmetry maintained by TAT-1/CHAT-1

Endocytic sorting is achieved through the formation of morphologically and functionally distinct sub-domains within early endosomes. cargoes destined for recycling are sorted to and transported through newly-formed tubular membranes,but the processes that regulate membrane tubulation are poorly understood. here,we identified a novel caenorhabditis elegans cdc50 family protein,chat-1,which acts as the chaperone of the tat-1 p4-atpase to regulate membrane phosphatidylserine (ps) asymmetry and endocytic transport. in chat-1 and tat-1 mutants,the endocytic sorting process is disrupted,leading to defects in both cargo recycling and degradation. tat-1 and chat-1 colocalize to the tubular domain of the early endosome,the tubular endocytic recycling compartment (erc),and the recycling endosome where ps is enriched on the cytosolic surface. loss of tat-1 and chat-1 function disrupts membrane ps asymmetry and abrogates the tubular membrane structure. our data suggest that chat-1 and tat-1 maintain membrane phosphatidylserine asymmetry,thus promoting membrane tubulation and regulating endocytic sorting and recycling. © 2010 chen et al.