Caenorhabditis elegans auxilin: a J-domain protein essential for clathrin-mediated endocytosis in vivo

The budding of clathrin-coated vesicles is essential for protein transport. After budding, clathrin must be uncoated before the Vesicles can fuse with other membranous structures. In vitro, the molecular chaperone Hsc70 uncoa ts clathrin-coated vesicles in an ATP-dependent process that requires a spe cific J-domain protein such as auxilin. However, there is little evidence t hat either Hsc70 or auxilin is essential in vivo. Here we show that C. eleg ans has a single auxilin homologue that is identical to mammalian auxilin i n its in vitro activity. When RNA-mediated interference (RNAi) is used to i nhibit auxilin expression in C. elegans, oocytes show markedly reduced rece ptor-mediated endocytosis of yolk protein tagged with green fluorescent pro tein (GFP). In addition, most of these worms arrest during larval developme nt, exhibit defective distribution of GFP-clathrin in many cell types, and show a marked change in clathrin dynamics, as determined by fluorescence re covery after photobleaching (FRAP). We conclude that auxilin is required fo r in vivo clathrin-mediated endocytosis and development in C. elegans.