Fig. 1. Overexpression of hVPS4^EQ induces enlarged endosomal vacuoles. Cryosections of non-transfected HeLa cells or cells transfected with GFP-hVPS4^wt or GFP-hVPS^EQ were labeled for GFP (10 nm gold). (A) In non-transfected cells, EEs appear as electron-lucent vacuoles containing few internal vesicles. Only rarely can an inward budding profile (i.e. forming internal vesicle) be observed (arrow). (B) hVPS4^wt is mainly cytosolic and the morphology of endosomal vacuoles (EV) is unaffected. (C,D) Overexpression of the ATPase-deficient hVPS4^EQ leads to enlarged EVs. Some EVs display lipid particles without a limiting membrane (C). In others, unusually many inward budding profiles are seen (arrows in D). M, mitochondrion; PM, plasma membrane. Scale bars, 200 nm.