Association of insulin-like growth factor 1 receptor with EHD1 and SNAP29

Ligand-induced receptor-mediated endocytosis plays a central role in regula ting signaling conveyed by tyrosine kinase receptors. This process depends on the recruitment of the adaptor protein 2 (AP-2) complex, clathrin, dynam in, and other accessory proteins to the ligand-bound receptor. We show here that besides AP-2 and clathrin, two other proteins participate in the endo cytic process of the insulin-like growth factor receptor (IGF-1R); they are EHD1, an Eps15 homology (EH) domain-containing protein 1, and SNAP29, a sy naptosomal-associated protein. EHD1 and SNAP29 form complexes with alpha -a daptin of AP-2 and co-localize in endocytic vesicles, indicating a role for them in endocytosis. EHD1 and SNAP29 interact directly with each other and are present in complexes with IGF-1R. After IGF-1 induction, EHD1 and IGF- 1R co-localize intracellularly. Overexpression of EHD1 in Chinese hamster o vary cells represses IGF-1-mediated signaling, as measured by mitogen-activ ated protein kinase phosphorylation and Akt phosphorylation, indicating tha t EHD1 plays a role as a down-regulator in IGF-1 signaling pathway.