Autophagy, cytoplasm-to-vacuole targeting pathway, and pexophagy in yeast and mammalian cells

The sequestration and delivery of cytoplasmic material to the yeast vacuole and mammalian lysosome require the dynamic mobilization of cellular membra nes and specialized protein machinery. Under nutrient deprivation condition s, double-membrane vesicles form around bulk cytoplasmic cargo destined for degradation and recycling in the vacuole/lysosome. A similar process funct ions to remove excess organelles under vegetative conditions in which they are no longer needed. Biochemical, morphological, and molecular genetic stu dies in yeasts and mammalian cells have begun to elucidate the molecular de tails of this autophagy process. In addition, the overlap of macroautophagy with the process of pexophagy and with the biosynthetic cytoplasm-to-vacuo le targeting pathway, which delivers the resident vacuolar hydrolase aminop eptidase I, indicates that these three pathways are related mechanistically . Identification and characterization of the autophagic/cytoplasm-to-vacuol e protein-targeting components: have revealed the essential roles for vario us functional classes of proteins, including a novel protein conjugation sy stem and the machinery for vesicle formation and fusion.