Hrs recruits clathrin to early endosomes

The hepatocyte growth factor-regulated tyrosine kinase substrate, Hrs, has been implicated in intracellular trafficking and signal transduction. Hrs c ontains a phosphatidylinositol 3-phosphate-binding FYVE domain that contrib utes to its endosomal targeting. Here we show that Hrs and EEA1, a FYVE dom ain protein involved in endocytic membrane fusion, are localized to differe nt regions of early endosomes. We demonstrate that Hrs co-localizes with cl athrin, and that the C-terminus of Hrs contains a functional clathrin box m otif that interacts directly with the terminal beta -propeller domain of cl athrin heavy chain. A massive recruitment of clathrin to early endosomes wa s observed in cells transfected with Hrs, but not with Hrs lacking the C-te rminus. Furthermore, the phosphatidylinositol 3-kinase inhibitor wortmannin caused the dissociation of both Hrs and clathrin from endosomes. While ove rexpression of Hrs did not affect endocytosis and recycling of transferrin, endocytosed epidermal growth factor and dextran were retained in early end osomes. These results provide a molecular mechanism for the recruitment of clathrin onto early endosomes and suggest a function for Hrs in trafficking from early to late endosomes.