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 case of infection, the HIV-1 virus takes advantage of the ESCRT-III complex for budding and exocytic cargos of viral proteins. SUBCELLULAR LOCATION: Cytoplasm, cytosol. TISSUE SPECIFICITY: Widely expressed. Expressed in brain, heart, skeletal muscle, spleen, kidney, liver, small intestine, pancreas, lung, placenta and leukocytes. In brain, it is expressed in cerebellum, cerebral cortex, medulla, spinal chord, occipital lobe, frontal lobe, temporal lobe and putamen. DISEASE: Defects in CHMP2B are the cause of frontotemporal dementia, chromosome 3-linked (FTD3). 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. Also known as: Chromatin-modifying protein 2b, CHMP2.5, Vacuolar protein sorting associated protein 2-2, Vps2-2, hVps2-2, Charged multivesicular body protein 2b.