charged multivesicular body protein 4B; chromatin-modifying protein 4B; CHMP4b; SNF7 homolog associated with Alix 1; SNF7-2; hSnf7-2; vacuolar protein sorting-associated protein 32-2; Vps32-2; hVps32-2 (CHMP4B, C20orf178, SHAX1)

Function

• component of ESCRT3 in the multivesicular body pathway
• within ESCRT3, serves as an acceptor for ESCRT1 complex
• interacts with CHMP2A, CHMP4A, CHMP4C, CHMP6 within ESCRT3
• interacts with ESCRT1 component PDCD6IP
• when overexpressed, membrane-assembled circular arrays of CHMP4B filaments can promote or stabilize negative curvature & outward budding
• interacts with CHMP6, CHMP4C & CHMP7
• interacts with VPS4A & VPS4B
• interaction with misfolded CFTR

Structure

• the acidic C-terminus & the basic N-termminus are thought to render the protein in a closed, soluble & inactive conformation through an autoinhibitory intramolecular interaction
• the open & active conformation, which enables membrane binding & oligomerization, is facilitated by interaction with other ESCRT components
• belongs to the SNF7 family

Compartment

cytoplasm, late endosome membrane

Expression

• widely expressed
• expressed in heart, skeletal muscle > brain, colon, thymus, spleen, kidney, liver, small intestine, placenta, lung, peripheral blood lymphocytes.

Pathology

• overexpression strongly inhibits HIV-1 release
• defects in CHMP4B are the cause of cataract posterior polar type 3

More general terms

• charged multivesicular body protein (CHMP)

Component of

• endosomal sorting complex required for transport-3 (ESCRT3)

Database

• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=128866
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:128866
• OMIM: https://mirror.omim.org/entry/605387
• OMIM: https://mirror.omim.org/entry/610897
• UniProt: http://www.uniprot.org/uniprot/Q9H444.html