Trs85 (Gsg1), a component of the TRAPP complexes, is required for the organization of the preautophagosomal structure during selective autophagy via the Cvt pathway.

Autophagosomes and Cvt vesicles are limited by two membrane layers. The biogenesis of these unconventional vesicles and the origin of their membranes are hardly understood. Here we identify in Saccharomyces cerevisiae Trs85, a nonessential component of the TRAPP complexes, to be required for the biogenesis of Cvt vesicles.

Atg21 is required for effective recruitment of Atg8 to the preautophagosomal structure during the Cvt pathway.

Atg21 and Atg18 are homologue yeast proteins. Whereas Atg18 is essential for the Cvt pathway and autophagy, a lack of Atg21 only blocks the Cvt pathway. Our proteinase protection experiments now demonstrate that growing atg21Delta cells fail to form proaminopeptidase I-containing Cvt vesicles.

Intravacuolar membrane lysis in Saccharomyces cerevisiae. Does vacuolar targeting of Cvt17/Aut5p affect its function?

The integral membrane protein Cvt17/Aut5p is a putative lipase essential for intravacuolar lysis of autophagic bodies. It is localized at the endoplasmic reticulum, from which it is targeted via the multivesicular body (MVB) pathway to intravacuolar MVB vesicles. Proteinase protection experiments now demonstrate that the Aut5 amino terminus is located in the cytosol, and the carboxyl terminus is located inside the ER lumen.

Mai1p is essential for maturation of proaminopeptidase I but not for autophagy.

We here identify Mai1p, a homologue of the autophagy protein Aut10p, as a novel component essential for proaminopeptidase I (proAPI) maturation under non-starvation conditions. In mai1Delta cells mature vacuolar proteinases are detectable and vacuolar acidification is normal. In mai1Delta cells autophagy occurs, though at a somewhat reduced level.