An Investigation into the Structural Basis of BIN1-mediated Recruitment and Regulation of Dynamin 2 During Endocytosis

Abstract

Endocytosis is a vital cellular process during which vesicles form at the plasma membrane to internalize nutrients, signaling molecules, and transmembrane proteins. Bridging integrator 1 (BIN1) is a key protein that forms a helical polymer around the necks of budding vesicles and interacts with dynamin 2, a large GTPase responsible for vesicle scission. While BIN1’s recruitment and regulation of dynamin 2 is critical for endocytosis to occur, little is known about BIN1’s structure and domain organization to evaluate the mechanism by which it carries out its functions. Therefore, this study aims to use cryogenic electron microscopy (cryo-EM) to (1) determine the 3D structure of BIN1 on lipid tubules and (2) BIN1 in complex with dynamin 2 on lipid tubules to evaluate the structural basis of BIN1's mechanism of action during endocytosis. Our hypothesis is that BIN1’s src-homology 3 (SH3) domain is exposed and extended outwards from the membrane to enable efficient recruitment of dynamin 2’s proline rich domain (PRD). Additionally, we anticipate that BIN1 will promote dynamin 2’s GTPase activity by co-assembling in an intercalated pattern with its SH3 domain, stabilizing dynamin 2’s PRD to promote dimerization of its GTPase dimers. This study lays the groundwork for understanding the SH3-PRD interaction and explores optimization approaches for achieving high-resolution structural data. Ultimately, our findings will provide valuable structural insights into the molecular coordination between BIN1 and dynamin 2 in membrane remodeling during endocytosis.