An Electron Microscopy Study into Vps1 and the role of its F-actin Binding Regions within Clathrin-mediated Endocytosis

Abstract

Abstract: Clathrin-mediated endocytosis is a conserved process utilised by metazoans and fungi for the internalisation of cell surface receptors into vesicles upon ligand binding. This is a vital process by which cells are able to communicate with other cells and there external environment. Transmission electron microscopy of endocytic sites in F-actin binding mutants of S. cerevisiae suggest an absolute requirement for Vps1p to bind F-actin in order to generate directional propagation of an invaginations against the internal osmotic pressure of the cell. Structural observations of endocytic pits by electron tomography revealed a dynamin-like structure indicative of a mode of scission analogous to that carried out by dynamin-1. Following this observation similarity searches were conducted between dynamin-1 and Vps1p revealing conservation of primary and secondary structure between the two proteins within the GTPase domain, middle domain and GTPase effector domain. Supported by recent findings the observations recorded here favour a model of scission that incorporates Vps1p in a manner that is comparable with its mammalian homologue, dynamin-1.