Stimulation of dynamin GTPase activity by amphiphysin.

Dynamin functions in the fission of endocytic pits in the process of clathrin-mediated endocytosis. Dynamin GTPase activity is essential for its fission activity, and it is stimulated by self-assembly as well as by interacting with its binding partners, such as microtubules, SH3 domain containing proteins, or inositol phospholipids. Amphiphysin 1, SH3 domain-containing binding partner of dynamin 1, is proposed to cooperatively function in endocytosis. Amphiphysin 1 is essential for dynamin-dependent synaptic vesicle recycling in the synapse, and it enhances dynamin-dependent vesicle formation in vitro. In order to elucidate the molecular mechanism underlying the amphiphysin's effect, we measured dynamin GTPase activity in the presence of both amphiphysin 1 and lipid membranes. We describe here in detail the procedure of the dynamin GTPase assay and the results demonstrating stimulatory effect of amphiphysin on dynamin GTPase activity, which is highly dependent on the liposome size.