Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 113, Issue 15, Pages 4039-4044Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1523926113
Keywords
mitophagy; TBK1; OPTN; ubiquitin; phosphorylation
Categories
Funding
- Deutsche Forschungsgemeinschaft [DI 931/3-1]
- Cluster of Excellence Macromolecular Complexes of the Goethe University Frankfurt [EXC115]
- LOEWE Grant Ub-Net
- LOEWE Centrum for Gene and Cell Therapy Frankfurt
- NIH-NINDS intramural program
- European Molecular Biology Organization (EMBO) long-term postdoctoral fellowship
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Selective autophagy of damaged mitochondria requires autophagy receptors optineurin (OPTN), NDP52 (CALCOCO2), TAX1BP1, and p62 (SQSTM1) linking ubiquitinated cargo to autophagic membranes. By using quantitative proteomics, we show that Tank-binding kinase 1 (TBK1) phosphorylates all four receptors on several autophagy-relevant sites, including the ubiquitin-and LC3-binding domains of OPTN and p62/SQSTM1 as well as the SKICH domains of NDP52 and TAX1BP1. Constitutive interaction of TBK1 with OPTN and the ability of OPTN to bind to ubiquitin chains are essential for TBK1 recruitment and kinase activation on mitochondria. TBK1 in turn phosphorylates OPTN's UBAN domain at S473, thereby expanding the binding capacity of OPTN to diverse Ub chains. In combination with phosphorylation of S177 and S513, this posttranslational modification promotes recruitment and retention of OPTN/TBK1 on ubiquitinated, damaged mitochondria. Moreover, phosphorylation of OPTN on S473 enables binding to pS65 Ub chains and is also implicated in PINK1-driven and Parkin-independent mitophagy. Thus, TBK1-mediated phosphorylation of autophagy receptors creates a signal amplification loop operating in selective autophagy of damaged mitochondria.
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