Understanding Periperal Membrane Protein Interactions | BPS Thematic Meeting

Understanding Peripheral Membrane Protein Interactions: Structure, Dynamics, Function and Therapy

Monday Speaker Abstracts

CONSTRICTING AND CLEAVING MEMBRANE NECKS WITH ESCRT-III AND VPS4 Winfried Weissenhorn 1 ; 1 University Grenoble Alpes, IBS, Grenoble, France The endosomal sorting complex for transport (ESCRT) is a highly conserved protein machinery that catalyzes a wide range of membrane remodeling processes such as vesicle formation at endosomes, budding of some enveloped viruses, membrane repair, late steps in cytokinesis and others. Common to all ESCRT-catalyzed processes is the recruitment of ESCRT-III and the ATPase VPS4, which form filaments on membranes that are remodeled and eventually disassembled by VPS4 leading to membrane constriction and cleavage. Although Eukaryotes express eleven ESCRT-III proteins called CHMP, our objectives are to demonstrate that a core complex composed of CHMP4 and/or CHMP2A and CHMP3 is sufficient to catalyze membrane fission and provide mechanistic insight into the process.We employ combined X-ray and HS AFM studies of the ESCRT-III adaptor protein Alix, which reveal that Alix dimers nucleate CHMP4B polymerization on membranes, which is likely a prerequisite for downstream polymerization of CHMP2A and CHMP3 in vivo. CryoEM structures of CHMP2A- CHMP3 copolymers ‘assembled’ within a lipid bilayer tube recapitulate the geometry of membrane neck structures generated during vesicle or virus budding and at the cytokinetic midbody. The structures demonstrate membrane interaction via electrostatic interactions and via amphipathic helices. Membrane interaction further leads to membrane thinning. Employing a ‘single’ molecule/polymer fluorescence assay and HS-AFM we show that CHMP2A-CHMP3 copolymers can constrict and cleave membranes. In conclusion, our data suggesst that CHMP2A-CHMP3 and VPS4 constitute a minimal membrane fission machinery.

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