Williams, G. L. | bioRxiv Science

bioRxiv2023

TBK1 is ubiquitinated by TRIM5alpha to assemble mitophagy machinery

Ubiquitination of mitochondrial proteins provides a basis for the downstream recruitment of mitophagy machinery, yet whether ubiquitination of the machinery itself contributes to mitophagy is unknown. Here, we show that K63-linked polyubiquitination of the key mitophagy regulator TBK1 is essential for its mitophagy functions. This modification is catalyzed by the ubiquitin ligase TRIM5. Mitochondrial damage triggers TRIM5s auto-ubiquitination and its interaction with ubiquitin-binding autophagy adaptors including NDP52, optineurin, and NBR1. Autophagy adaptors, along with TRIM27, enable TRIM5 to engage with TBK1. TRIM5 with intact ubiquitination function is required for the proper accumulation of active TBK1 on damaged mitochondria in Parkin-dependent and Parkin-independent mitophagy pathways. Additionally, we show that TRIM5 can directly recruit autophagy initiation machinery to damaged mitochondria. Our data support a model in which TRIM5 provides a self-amplifying, mitochondria-localized, ubiquitin-based, assembly platform for TBK1 and mitophagy adaptors that is ultimately required to recruit the core autophagy machinery.

cell biology↗

bioRxiv2021

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.

cell biology↗