Essential role of the dynamin pleckstrin homology domain in receptor-mediated endocytosis

Pleckstrin homology (PH) domains are found in numerous membrane-associated proteins and have been implicated in the mediation of protein-protein and p rotein-phospholipid interactions. Dynamin, a GTPase required for clathrin-d ependent endocytosis, contains a PH domain which binds to pbosphoinositides and participates in the interaction between dynamin and the beta gamma sub units of heterotrimeric G proteins. The PH domain is essential for expressi on of phosphoinositide-stimulated GTPase activity of dynamin in vitro, but its involvement in the endocytic process is unknown, We expressed a series of dynamin PH domain mutants in cultured cells and determined their effect on transferrin uptake by those cells, Endocytosis is blocked in cells expre ssing a PH domain deletion mutant and a point mutant that fails to interact with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P-2]. In contrast, expr ession of a point mutant with unimpaired PI(4,5)P-2 interaction has no effe ct on transferrin uptake. These results demonstrate the significance of the PH domain for dynamin function and suggest that its role may be to mediate interactions between dynamin and phosphoinositides.