Ccz1p/Aut11p/Cvt16p is essential for autophagy and the cvt pathway

In a reverse genetics screen, we here identify Cezip as an essential component of the cvt pathway and autophagy. Cezip is identical with the so far unknown Cvt16p. GFP-Aut7p, a specific cargo of autophagosomes, accumulates in ccz1Delta cells at punctate, vesicular structures in the cytosol, suggesting a block in the autophagic pathway prior to vacuolar fusion of autophagosomes. Proteinase protection experiments using hypotonically lysed ccz1Delta spheroplasts demonstrate that proamino-peptidase 1, another specific cargo of autophagy and the cvt pathway, is trapped inside membrane-enclosed vesicles. Taken together our findings are compatible with a function of Ccz1p in vacuolar fusion of cvt vesicles and autophagosomes. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.