The PX-BAR membrane-remodeling unit of sorting nexin 9

Abstract

Sorting nexins (SNXs) form a family of proteins known to interact with components in the endosomal system and to regulate various steps of vesicle transport. Sorting nexin 9 (SNX9) is involved in the late stages of clathrin-mediated endocytosis in non-neuronal cells, where together with the GTPase dynamin, it participates in the formation and scission of the vesicle neck. We report here crystal structures of the functional membrane-remodeling unit of SNX9 and show that it efficiently tubulates lipid membranes in vivo and in vitro. Elucidation of the protein superdomain structure, together with mutational analysis and biochemical and cell biological experiments, demonstrated how the SNX9 PX and BAR domains work in concert in targeting and tubulation of phosphoinositide-containing membranes. The study provides insights into the SNX9-induced membrane modulation mechanism.

Dual Role of BAR Domain-containing Proteins in Regulating Vesicle Release Catalyzed by the GTPase, Dynamin-2

“…3A), to stimulate Dyn2-catalyzed vesicle release. Unlike amphiphysin and endophilin, which encode N-BAR domains, SNX9 encodes a PX-BAR domain, known to be less efficient in curvature generation (42,43). Consistent with these classifications, full-length amphiphysin and endophilin efficiently generated long membrane tubules from SUPER templates at submicromolar concentrations (Fig.…”

Structural and functional characterization of the two phosphoinositide binding sites of PROPPINs, a β-propeller protein family

“…Sulfate ions often indicate the positions of the phosphates of phosphoinositide head groups (29)(30)(31). Sulfate site 3 is located in proximity to a negatively charged surface patch, which would be repulsive for membrane association, and thus is unlikely to represent a phosphoinositide binding site (Fig.…”

Molecular Structure, Function, and Dynamics of Clathrin-Mediated Membrane Traffic

“…An unstructured linker has binding sites for AP2 appendages and clathrin; it connects the BAR domain to a carboxy-terminal SH3 domain, which binds the proline-rich, carboxy-terminal regions of two membranedirected enzymes, the dynamin GTPase and the synaptojanin lipid phosphatase Micheva et al 1997;Verstreken et al 2003). Snx9, found in most cell types, has the same domain structure and functionalities but arranged in the opposite order and with the addition of a PIP-binding PX domain just amino terminal to the BAR domain (Pylypenko et al 2007;Wang et al 2008;van Weering et al 2012). …”