(PINS) "Understanding Selective Mitophagy" - Progress in Neuroscience Seminar Series

Wade Harper Ph.D., Professor of Cell Biology, Harvard Medical School The ubiquitin ligase Parkin, protein kinase PINK1, USP30 deubiquitylase, and p97 segregase function together to regulate turnover of damaged mitochondria via mitophagy, but our mechanistic understanding in neurons is limited. We have used induced neurons (iNeurons) derived from embryonic stem cells together with quantitative proteomics to reveal the dynamics and specificity of Parkin-dependent mitochondrial outer membrane protein ubiquitylation under endogenous expression conditions. Targets showing elevated ubiquitylation in USP30-/- iNeurons are concentrated in components of the mitochondrial translocon, and the ubiquitylation kinetics of the vast majority of Parkin targets are unaffected, correlating with a modest kinetic acceleration in accumulation of pS65-Ub and mitophagic flux upon mitochondrial depolarization without USP30. Basally, ubiquitylated translocon import substrates accumulate, suggesting a quality control function for USP30. p97 was dispensable for Parkin-dependent mitochondrial ubiquitylation in iNeurons. We will discuss how the biochemical landscape of Parkin action of mitochondria promotes capture by the autophagy system.