Fig. 1.

A schematic overview of autophagy and the Cvt pathway in yeast. The Cvt pathway is an autophagy-related process that operates under vegetative conditions and plays a biosynthetic role, delivering resident hydrolases such as aminopeptidase I (Ape1) to the yeast vacuole. The Cvt vesicle is approximately 150 nm in diameter and appears to exclude cytosol. In yeast, autophagy is induced by starvation, and the autophagosome, which is 300-900 nm in diameter, sequesters cytoplasm, including organelles; this pathway is also used for specific transport of prApe1. Both types of vesicle are thought to originate from the pre-autophagosomal structure (PAS). Upon completion, the vesicles fuse with the lysosome-like vacuole, releasing the inner vesicle, termed a Cvt body or autophagic body. These subvacuolar vesicles are broken down, allowing maturation of prApe1 and degradation of cytoplasm, with recycling of the resulting macromolecules.