Autophagy in protein and organelle turnover.

Macroautophagy is an evolutionarily conserved degradation system in the cell. In autophagy, intracellular components are sequestered by autophagosomes and subsequently degraded upon fusion with lysosomes. Genetic analysis of autophagy in mammals has revealed that autophagy is important for various physiological processes, such as adaptive responses to starvation, embryogenesis, quality control of intracellular proteins and organelles, tumor suppression, degradation of intracellular pathogens, and anti-aging. In this review I describe the various roles of autophagy, with a particular focus on the turnover of cytoplasmic proteins and organelles.