The PINK1-PARKIN Mitochondrial Ubiquitylation Pathway Drives a Program of OPTN/NDP52 Recruitment and TBK1 Activation to Promote Mitophagy

Damaged mitochondria are detrimental to cellular homeostasis. One mechanism for removal of damaged mitochondria involves the PINK1-PARKIN pathway, which poly-ubiquitylates damaged mitochondria to promote mitophagy. We report that assembly of ubiquitin chains on mitochondria triggers autophagy adaptor recruitment concomitantly with activation of the TBK1 kinase, which physically associates with OPTN, NDP52, and SQSTM1. TBK1 activation in HeLa cells requires OPTN and NDP52 and OPTN ubiquitin chain binding. In addition to the known role of S177 phosphorylation in OPTN on ATG8 recruitment, TBK1-dependent phosphorylation on S473 and S513 promotes ubiquitin chain binding in vitro as well as TBK1 activation, OPTN mitochondrial retention, and efficient mitophagy in vivo. These data reveal a self-reinforcing positive feedback mechanism that coordinates TBK1-dependent autophagy adaptor phosphorylation with the assembly of ubiquitin chains on mitochondria to facilitate efficient mitophagy, and mechanistically links genes mutated in Parkinson’s disease and amyotrophic lateral sclerosis in a common selective autophagy pathway. [Display omitted] •PINK1-PARKIN pathway promotes TBK1 activation via OPTN and NDP52•Mitochondrial ubiquitylation templates TBK1 activation via OPTN/NDP52 recruitment•TBK1 phosphorylates S473 and S513 in OPTN to enhance UB chain binding in vitro•TBK1 and OPTN/NDP52 promote mitophagy in HeLa cells Mitochondrial damage promotes PINK1-PARKIN-dependent mitochondrial ubiquitylation and mitophagy. Heo et al. report that mitochondrial damage activates the kinase TBK1, which phosphorylates autophagy adaptors OPTN, NDP52, and SQSTM1, and in the case of OPTN is shown to increase ubiquitin binding and recruitment to damaged mitochondria to promote mitophagy.