The effect of SH3 domains on dynamin activity and oligomerisation

Abstract

Dynamin is a GTPase enzyme that mediates vesicle fission during endocytosis to release new vesicles into the cell cytoplasm. It is recruited to sites of endocytosis in cells where it promotes vesicle fission by assembling into a collar around the vesicle neck. Dynamin is regulated by binding to proteins containing src homology 3 (SH3) domain, which stimulate its oligomerisation into rings with an associated increase in dynamin GTPase activity. However, each SH3 domain has been inconsistently studied in isolation from the others and sometimes as part of the full-length protein. This study revealed important new insights into dynamin modulation, isoform functional diversity and therefore potential function in endocytosis. Through a systematic approach, the observations overturn conclusions of several previous studies and reveal many new insights into dynamin activation and the remarkable diversity in the way SH3 domains stimulate dynamin. The existence of a previously unknown assembly independent allosteric mechanism to stimulate dynamin GTPase is revealed. The work highlights the SH3 domain of SNX9 as the most potent and consistent in vitro regulator of dynamin oligomerisation and activity. It also mapped the unique binding mechanism for SNX9 on dynamin I and revealed that this interaction is potentially phospho-regulated.