Autophagy is generally known as a process involved in the degradation of bulk cytoplasmic components that are non-specifically sequestered into an autophagosome, where they are sequestered into double-membrane vesicles and delivered to the degradativ ...
Autophagy is generally known as a process involved in the degradation of bulk cytoplasmic components that are non-specifically sequestered into an autophagosome, where they are sequestered into double-membrane vesicles and delivered to the degradative organelle, the lysosome/vacuole, for breakdown and eventual recycling of the resulting macromolecules. In contrast to autophagy, however, the Cvt pathway is a highly selective process that involves the sequestration of at least two specific cargos that are resident vacuolar hydrolases, aminopeptidase I (Ape1) and alpha-mannosidase (Ams1). These proteins are sequestered within a double-membrane vesicle, termed a Cvt vesicle. The Cvt vesicle is fairly consistent in size, and is much smaller than the autophagosome, being 140-160 nm in diameter. The prApe1 is sequestered within either Cvt vesicles or autophagosomes, depending on the nutrient conditions, and delivered to the vacuole. Autophagy and the Cvt pathway are topologically and mechanistically similar and share most of the same machinery. The Ape1 complex is ultimately enwrapped within either Cvt vesicles or autophagosomes at the perivacuolar PAS. The receptor protein Atg19 binds to the Ape1 complex through the prApe1 propeptide to form the Cvt complex in the cytosol. In the absence of Atg19, prApe1 can form an Ape1 complex, but does not localise at the PAS. Atg19 is a peripheral membrane protein with differing binding sites for both Ape1 and Ams1. The Atg8-binding region in the yeast proteins is this very C-terminal residues [3].
