Regulation of Dynamin I GTPase Activity by G Protein βγ Subunits and Phosphatidylinositol 4,5-Bisphosphate

Dynamin I is a 100-kDa GTPase that plays an important role in the recycling of synaptic vesicles. Hydrolysis of GTP by dynamin is thought to be a critical step in fission of coated pits to form coated vesicles. We report that the heterotrimeric G protein βγ subunit complex (Gβγ) and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) are negative and positive regulators of dynamin GTPase activity, respectively. Furthermore, the apparent affinity of dynamin for Gβγ is substantially enhanced by PtdIns(4,5)P2. However, the GTPase activity of oligomeric dynamin is unaffected by Gβγ. The effects of heterotrimeric G proteins on endocytosis may thus be mediated directly and not involve more remote aspects of their signaling properties. Dynamin I is a 100-kDa GTPase that plays an important role in the recycling of synaptic vesicles. Hydrolysis of GTP by dynamin is thought to be a critical step in fission of coated pits to form coated vesicles. We report that the heterotrimeric G protein βγ subunit complex (Gβγ) and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) are negative and positive regulators of dynamin GTPase activity, respectively. Furthermore, the apparent affinity of dynamin for Gβγ is substantially enhanced by PtdIns(4,5)P2. However, the GTPase activity of oligomeric dynamin is unaffected by Gβγ. The effects of heterotrimeric G proteins on endocytosis may thus be mediated directly and not involve more remote aspects of their signaling properties.