Auto-Inhibition Effects in Regulating Membrane Curvature Sensing and Generation of Bar Domain Containing Protein

Abstract

The question of how membrane curvature (MC) is involved in generating and maintaining spatial organization and activity of cells is increasingly being addressed. MC is regulated in part by peripheral membrane proteins, such as those that contain BAR domains and amphiphatic membrane-binding helices. However, the mechanisms underlying membrane curvature sensing and generation (MC S&G) currently are not fully understood. Based on recently published findings, we hypothesize that intra-molecular auto-inhibition modulate MC S&G in BAR domain containing proteins. Specifically, we here focus on the N-BAR domain containing protein endophilin, which is known to be involved in both clathrin-dependent and clathrin independent endocytotic pathways. Endophilin interacts with dynamin and synaptojanin via a C-terminal SH3 domain.To evaluate auto-inhibition in influencing MC S&G of endophilin, we compare the consequences of the binding of two different proline rich peptides to the endophilin SH3 domains. We found that these two peptides increase endophilin membrane binding affinity to differing degrees that also were dependent on membrane composition. Furthermore, we observed that the more effective peptide released both binding affinity and curvature sensing capability, while the other peptide merely liberated endophilin membrane binding affinity. Finally, we propose a molecular interaction model to interpret these phenomena.