Atg32 Confers Selective Mitochondrial Sequestration as a Cargo for Autophagy

Mitochondria are organelles that supply a large amount of energy required for cellular activities. Accumulation of dysfunctional mitochondria within cells inhibits cellular functions and causes several diseases. Thus, the cell has devised specific mechanisms to ensure proper quality and quantity control of this organelle. Mitochondrial autophagy (mitophagy) is thought to be one of the primary mechanisms for mitochondrial quality control that selectively eliminate dysfunctional or excess mitochondria via an autophagic process. ATG32 is a mitophagy-specific gene identified by a yeast genome-wide screen for mitophagy. Atg32, a protein encoded by ATG32, is a transmembrane protein localized in the mitochondrial outer membrane. During mitophagy induction, Atg32 functions as a mitochondrial receptor protein that interacts with cytosolic adaptor protein Atg11, which recruits mitochondria to the autophagic machinery for degradation. In this chapter, we describe the molecular mechanism and physiology of mitophagy in yeast, with an emphasis on the role of Atg32.