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From Proteopedia
VPS4B MIT-CHMP2B Complex
Structural highlights
Disease[CHM2B_HUMAN] Defects in CHMP2B are the cause of frontotemporal dementia, chromosome 3-linked (FTD3) [MIM:600795]. FTD3 is characterized by an onset of dementia in the late 50's initially characterized by behavioral and personality changes including apathy, restlessness, disinhibition and hyperorality, progressing to stereotyped behaviors, non-fluent aphasia, mutism and dystonia, with a marked lack of insight. The brains of individuals with FTD3 have no distinctive neuropathological features. They show global cortical and central atrophy, but no beta-amyloid deposits.[1] Defects in CHMP2B are the cause of amyotrophic lateral sclerosis type 17 (ALS17) [MIM:614696]. An adult-onset progressive neurodegenerative disorder with predominantly lower motor neuron involvement, manifest as muscle weakness and wasting of the upper and lower limbs, bulbar signs, and respiratory insufficiency.[2] [3] Function[VPS4B_HUMAN] Involved in late steps of the endosomal multivesicular bodies (MVB) pathway. Recognizes membrane-associated ESCRT-III assemblies and catalyzes their disassembly, possibly in combination with membrane fission. Redistributes the ESCRT-III components to the cytoplasm for further rounds of MVB sorting. MVBs contain intraluminal vesicles (ILVs) that are generated by invagination and scission from the limiting membrane of the endosome and mostly are delivered to lysosomes enabling degradation of membrane proteins, such as stimulated growth factor receptors, lysosomal enzymes and lipids. In conjunction with the ESCRT machinery also appears to function in topologically equivalent membrane fission events, such as the terminal stages of cytokinesis and enveloped virus budding (HIV-1 and other lentiviruses).[4] [5] [6] [CHM2B_HUMAN] Probable core component of the endosomal sorting required for transport complex III (ESCRT-III) which is involved in multivesicular bodies (MVBs) formation and sorting of endosomal cargo proteins into MVBs. MVBs contain intraluminal vesicles (ILVs) that are generated by invagination and scission from the limiting membrane of the endosome and mostly are delivered to lysosomes enabling degradation of membrane proteins, such as stimulated growth factor receptors, lysosomal enzymes and lipids. The MVB pathway appears to require the sequential function of ESCRT-O, -I,-II and -III complexes. ESCRT-III proteins mostly dissociate from the invaginating membrane before the ILV is released. The ESCRT machinery also functions in topologically equivalent membrane fission events, such as the terminal stages of cytokinesis and the budding of enveloped viruses (HIV-1 and other lentiviruses). ESCRT-III proteins are believed to mediate the necessary vesicle extrusion and/or membrane fission activities, possibly in conjunction with the AAA ATPase VPS4. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe ESCRT (endosomal sorting complex required for transport) pathway is required for terminal membrane fission events in several important biological processes, including endosomal intraluminal vesicle formation, HIV budding and cytokinesis. VPS4 ATPases perform a key function in this pathway by recognizing membrane-associated ESCRT-III assemblies and catalysing their disassembly, possibly in conjunction with membrane fission. Here we show that the microtubule interacting and transport (MIT) domains of human VPS4A and VPS4B bind conserved sequence motifs located at the carboxy termini of the CHMP1-3 class of ESCRT-III proteins. Structures of VPS4A MIT-CHMP1A and VPS4B MIT-CHMP2B complexes reveal that the C-terminal CHMP motif forms an amphipathic helix that binds in a groove between the last two helices of the tetratricopeptide-like repeat (TPR) of the VPS4 MIT domain, but in the opposite orientation to that of a canonical TPR interaction. Distinct pockets in the MIT domain bind three conserved leucine residues of the CHMP motif, and mutations that inhibit these interactions block VPS4 recruitment, impair endosomal protein sorting and relieve dominant-negative VPS4 inhibition of HIV budding. Thus, our studies reveal how the VPS4 ATPases recognize their CHMP substrates to facilitate the membrane fission events required for the release of viruses, endosomal vesicles and daughter cells. ESCRT-III recognition by VPS4 ATPases.,Stuchell-Brereton MD, Skalicky JJ, Kieffer C, Karren MA, Ghaffarian S, Sundquist WI Nature. 2007 Oct 11;449(7163):740-4. PMID:17928862[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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