Interactomic analysis reveals a new homeostatic role for the HIV restriction factor TRIM5α in mitophagy

The protein TRIM5 has multiple roles in anti-retroviral defense, but the mechanisms underlying TRIM5 action are unclear. Here, we used an APEX2-based proteomics approach to identify TRIM5-interacting proteins. Analysis of the TRIM5 interactome found proteins participating in a wide variety of cellular functions including regulating antiviral signaling pathways. We used this data set to uncover a novel role for TRIM5 in mitophagy, an autophagy-based mode of mitochondrial quality control that is compromised in multiple human diseases. Mitochondrial damage triggered the relocalization of TRIM5 to ER-mitochondria contact sites where TRIM5 colocalized with markers of autophagy initiation and autophagosome biogenesis. Furthermore, we found that TRIM5 knockout attenuated both Parkin-dependent and Parkin-independent mitophagy by preventing the recruitment of autophagy regulators FIP200 and ATG13 to unhealthy mitochondria. Finally, TRIM5 knockout cells showed reduced mitochondrial function under basal conditions and were more susceptible to uncontrolled immune activation and cell death in response to mitochondrial damage than were wild type cells. Taken together, our studies have identified a homeostatic role for a protein previously recognized exclusively for its antiviral actions.