Ubiquitinated protein deposits (red) build up in the absence of autophagy.
During autophagy, the cell gobbles up its own internal components into membranous structures called autophagosomes, which fuse with multivesicular bodies (MVBs) before delivery to lysosomes, where the sequestered material is degraded. Autophagy is particularly important at times of cell stress and energy depletion, when the cell must recycle old organelles and cytoplasmic proteins to provide a source of amino acids. Even unstressed cells, however, probably clean house regularly using a low level of autophagy.
Those autophagy vesicles—the MVBs—were recently linked to a form of dementia. A family with frontotemporal dementia (FTD) was found to have mutations in an MVB-associated protein called CHMP2B. CHMP2B is a subunit of the ESCRT complexes, which sort ubiquitinated endocytosed proteins into MVBs for degradation...
