1. A RAB7A phosphoswitch coordinates Rubicon Homology protein regulation of Parkin-dependent mitophagy.
- Author
-
Tudorica, Dan, Basak, Bishal, Puerta Cordova, Alexia, Khuu, Grace, Rose, Kevin, Lazarou, Michael, Holzbaur, Erika, and Hurley, James
- Subjects
Mitophagy ,Humans ,rab7 GTP-Binding Proteins ,Phosphorylation ,Ubiquitin-Protein Ligases ,Protein Serine-Threonine Kinases ,rab GTP-Binding Proteins ,HeLa Cells ,Protein Binding ,Intracellular Signaling Peptides and Proteins ,Autophagy-Related Proteins ,Mitochondria ,HEK293 Cells - Abstract
Activation of PINK1 and Parkin in response to mitochondrial damage initiates a response that includes phosphorylation of RAB7A at Ser72. Rubicon is a RAB7A binding negative regulator of autophagy. The structure of the Rubicon:RAB7A complex suggests that phosphorylation of RAB7A at Ser72 would block Rubicon binding. Indeed, in vitro phosphorylation of RAB7A by TBK1 abrogates Rubicon:RAB7A binding. Pacer, a positive regulator of autophagy, has an RH domain with a basic triad predicted to bind an introduced phosphate. Consistent with this, Pacer-RH binds to phosho-RAB7A but not to unphosphorylated RAB7A. In cells, mitochondrial depolarization reduces Rubicon:RAB7A colocalization whilst recruiting Pacer to phospho-RAB7A-positive puncta. Pacer knockout reduces Parkin mitophagy with little effect on bulk autophagy or Parkin-independent mitophagy. Rescue of Parkin-dependent mitophagy requires the intact pRAB7A phosphate-binding basic triad of Pacer. Together these structural and functional data support a model in which the TBK1-dependent phosphorylation of RAB7A serves as a switch, promoting mitophagy by relieving Rubicon inhibition and favoring Pacer activation.
- Published
- 2024