Mitochondria-Anchored Receptor Atg32 Mediates Degradation of Mitochondria via Selective Autophagy

Mitochondria are essential organelles that produce most of the energy for a cell, but concomitantly accumulate oxidative damage. Degradation of damaged mitochondria is critical for cell homeostasis, and this process is thought to be mediated by mitophagy, an autophagy-related pathway specific for mitochondria. However, whether mitochondria are selectively degraded, and how the autophagic machinery is targeted to mitochondria, remain largely unknown. Here we demonstrate that, in post-log phase cells under respiratory conditions, a substantial fraction of mitochondria are exclusively sequestered as cargoes and transported to the vacuole, a lytic compartment in yeast, in an autophagy-dependent manner. Interestingly, we found Atg32, a mitochondria-anchored protein essential for mitophagy that is induced during respiratory growth. In addition, our data suggest that Atg32 interacts with Atg8 and Atg11, autophagy-related proteins critical for recognition of cargo receptors. We propose that Atg32 acts as a mitophagy-specific receptor and regulates selective degradation of mitochondria.