Two different axes CALCOCO2-RB1CC1 and OPTN-ATG9A initiate PRKN-mediated mitophagy

Autophagy. 2020 Nov;16(11):2105-2107. doi: 10.1080/15548627.2020.1815457. Epub 2020 Sep 7.


PINK1 and PRKN, proteins mutated in Parkinson disease, selectively amplify ubiquitin signals on damaged mitochondria for elimination via mitophagy. Because all five macroautophagy/autophagy receptors in mammals possess domains binding to ubiquitin and Atg8-family proteins, they were thought to recruit Atg8-family protein labeled phagophores from a cytosolic pool. However, our recent findings show that, in addition to Atg8-family protein binding, two of the receptors CALCOCO2 and OPTN interact with RB1CC1 and ATG9A, respectively, indicating that two different axes, CALCOCO2-RB1CC1 and OPTN-ATG9A, can initiate de novo biogenesis of autophagic membranes on ubiquitin-coated damaged mitochondria. These results explain the critical roles of the autophagy receptors CALCOCO2 and OPTN in mitochondrial degradation, and their abilities to simultaneously bind multiple autophagy core proteins propose a new function, i.e. a scaffold to build multivalent interactions for the orchestrated assembly of autophagy proteins near the ubiquitinated cargo.

Abbreviations: ATG: autophagy-related; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CRABP2: cellular retinoic acid binding protein 2; LIR: MAP1LC3/LC3-interacting region; MAP1LC3: microtubule associated protein 1 light chain 3; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SNIPER: specific and nongenetic IAP-dependent protein eraser; SQSTM1/p62: sequestosome 1; ULK: unc-51 like autophagy activating kinase.

Keywords: Mitochondria; PINK1; Parkin; Parkinson’s disease; ubiquitin.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Autophagy / physiology*
  • Autophagy-Related Proteins / metabolism*
  • Cell Cycle Proteins / metabolism
  • Humans
  • Membrane Transport Proteins / metabolism
  • Mitochondria / metabolism
  • Mitophagy / physiology*
  • Ubiquitin-Protein Ligases / metabolism*


  • Autophagy-Related Proteins
  • Cell Cycle Proteins
  • Membrane Transport Proteins
  • OPTN protein, human
  • RB1CC1 protein, human
  • Ubiquitin-Protein Ligases
  • parkin protein

Grants and funding

This work was supported by the Japan Society for the Promotion of Science [JP18H05500]; Japan Society for the Promotion of Science [JP18K06237]; National Institute of Neurological Disorders and Stroke intramural research program.