Hrs-2 regulates receptor-mediated endocytosis via interactions with Eps15

Hrs-a, via interactions with SNAP-25, plays a regulatory role on the exocyt ic machinery. We now show that Hrs-a physically interacts with Eps15, a pro tein required for receptor-mediated endocytosis. The Hrs-2/Eps15 interactio n is calcium dependent, inhibited by SNAP-25 and alpha-adaptin, and results in the inhibition of receptor-mediated endocytosis. Immunoelectron microsc opy reveals Hrs-2 localization on the limiting membrane of multivesicular b odies, organelles in the endosomal pathway. These data show that Hrs-8 regu lates endocytosis, delineate a biochemical pathway (Hrs-2-Eps15-AP2) in whi ch Hrs-a functions, and suggest that Hrs-a acts to provide communication be tween endo- and exocytic processes.