Association of the Endosomal Sorting Complex ESCRT-II with the Vps20 Subunit of ESCRT-III Generates a Curvature-sensitive Complex Capable of Nucleating ESCRT-III Filaments

• Published in: The Journal of biological chemistry Vol. 286; no. 39; pp. 34262 - 34270
• Main Authors: Fyfe, Ian, Schuh, Amber L., Edwardson, J. Michael, Audhya, Anjon
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.09.2011; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Atomic Force Microscopy; Caenorhabditis elegans - chemistry; Caenorhabditis elegans - genetics; Caenorhabditis elegans - metabolism; Caenorhabditis elegans Proteins - chemistry; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Cell Membrane - chemistry; Cell Membrane - genetics; Cell Membrane - metabolism; Endosomal Sorting Complexes Required for Transport - chemistry; Endosomal Sorting Complexes Required for Transport - genetics; Endosomal Sorting Complexes Required for Transport - metabolism; Endosomes; ESCRT; Lipid Bilayers - chemistry; Liposomes - chemistry; Membrane Biology; Membrane Curvature; Membrane Fusion; Membrane Trafficking; Protein Structure; Membrane Trafficking; Membrane Fusion; ESCRT; Membrane Curvature; Atomic Force Microscopy; Protein Structure; Endosomes
• DOI: 10.1074/jbc.M111.266411
• ISSN: 0021-9258

The scission of membranes necessary for vesicle biogenesis and cytokinesis is mediated by cytoplasmic proteins, which include members of the ESCRT (endosomal sorting complex required for transport) machinery. During the formation of intralumenal vesicles that bud into multivesicular endosomes, the ESCRT-II complex initiates polymerization of ESCRT-III subunits essential for membrane fission. However, mechanisms underlying the spatial and temporal regulation of this process remain unclear. Here, we show that purified ESCRT-II binds to the ESCRT-III subunit Vps20 on chemically defined membranes in a curvature-dependent manner. Using a combination of liposome co-flotation assays, fluorescence-based liposome interaction studies, and high-resolution atomic force microscopy, we found that the interaction between ESCRT-II and Vps20 decreases the affinity of ESCRT-II for flat lipid bilayers. We additionally demonstrate that ESCRT-II and Vps20 nucleate flexible filaments of Vps32 that polymerize specifically along highly curved membranes as a single string of monomers. Strikingly, Vps32 filaments are shown to modulate membrane dynamics in vitro, a prerequisite for membrane scission events in cells. We propose that a curvature-dependent assembly pathway provides the spatial regulation of ESCRT-III to fuse juxtaposed bilayers of elevated curvature. Background: The ESCRT (endosomal sorting complex required for transport) machinery governs the formation of multivesicular endosomes. Results: A complex formed by ESCRT-II and Vps20 directs ESCRT-III polymerization specifically to membranes of elevated curvature. Conclusion: Curvature sensing by components of the ESCRT machinery spatially restricts the scission activity of ESCRT-III. Significance: These findings highlight a new regulatory mechanism that controls ESCRT function.