Function: Component of the ESCRT-III complex, which is required for multivesicular bodies (MVBs) formation and sorting of endosomal cargo proteins into MVBs. The MVB pathway mediates delivery oftransmembrane proteins into the lumen of the lysosome for degradation. The ESCRT-III complex is probably involved in the concentration of MVB cargo. In the ESCRT-III complex, it probably serves as an acceptor for ESCRT-I complex on endosomal membranes. In case of infection, the HIV-1 virus takes advantage of the ESCRT-III complex for budding and exocytic cargos of viral proteins, via the association of CHMP4 proteins with PDCD6IP/AIP1, a protein directly recruited by HIV-1 p6 protein that functions at sites of viral Gag assembly and budding.
Subcellular location: Cytoplasm.
Tissue specificity: CHMP4B: Widely expressed. Expressed at higher level in heart and skeletal muscle. Also expressed in brain, colon, thymus, spleen, kidney, liver, small intestine, placenta, lung and peripheral blood lymphocytes.
Tissue specificity: CHMP4C: Expressed in heart, spleen and kidney. DISEASE: Defects in CHMP4B are the cause of posterior polar cataract type 3 (CTPP3). Cataract is the most frequent cause of visual impairment and blindness worldwide. Posterior polar cataract is a distinctive opacity located at the back of the lens. Because of its proximity to the optical center of the eye, posterior polar cataract can have a marked effect on visual acuity.
Miscellaneous: Its overexpression strongly inhibits HIV-1 release. Also known as: CHMP4B: Chromatin-modifying protein 4b, Vacuolar protein-sorting-associated protein 7-2, SNF7-2, hSnf7-2, SNF7 homolog associated with Alix 1, hVps32, SHAX1, Charged multivesicular body protein 4b. CHMP4C: Chromatin modifying protein 4c, Vacuolar protein-sorting-associated protein 7-3, SNF7-3, hSnf7-3, SNF7 homolog associated with Alix 3, SHAX3, Charged multivesicular body protein 4c.