USP 8 regulates mitophagy by removing K 6‐linked ubiquitin conjugates from parkin

Abstract

Mutations in the Park2 gene, encoding the E3 ubiquitin-ligase parkin, are responsible for a familial form of Parkinson's disease (PD). Parkin-mediated ubiquitination is critical for the efficient elimination of depolarized dysfunctional mitochondria by autophagy (mitophagy). As damaged mitochondria are a major source of toxic reactive oxygen species within the cell, this pathway is believed to be highly relevant to the pathogenesis of PD. Little is known about how parkin-mediated ubiquitination is regulated during mitophagy or about the nature of the ubiquitin conjugates involved. We report here that USP8/UBPY, a deubiquitinating enzyme not previously implicated in mitochondrial quality control, is critical for parkin-mediated mitophagy. USP8 preferentially removes non-canonical K6-linked ubiquitin chains from parkin, a process required for the efficient recruitment of parkin to depolarized mitochondria and for their subsequent elimination by mitophagy. This work uncovers a novel role for USP8-mediated deubiquitination of K6-linked ubiquitin conjugates from parkin in mitochondrial quality control.

The E3 Ubiquitin Ligase Parkin Is Recruited to the 26 S Proteasome via the Proteasomal Ubiquitin Receptor Rpn13

“…siRNA Transfections, Western Blot Analyses, and Fixed Cell Immunofluorescence-All siRNA transfections, Western blot analyses, and fixed cell immunofluorescence in U2OS cells stably expressing GFP-parkin were performed as previously described (14). Nontargeting or Rpn13 smartPool siRNA (Qiagen) were used at a final concentration of 10 nM.…”

“…Indeed, parkinmediated ubiquitination appears to function in several distinct cellular pathways, depending on the number and type of Ub modifications involved. Substrate monoubiquitination by parkin plays a role in receptor trafficking (8), whereas polyubiquitination by Lys-6-, Lys-27-, and Lys-63-linked Ub chains has been suggested to play a role in inclusion formation and mitophagy (12)(13)(14). However, proteasomal degradation by parkin-mediated Lys-48-linked substrate polyubiquitination has been the most extensively studied function of parkin.…”

Autophagosome dynamics in neurodegeneration at a glance

“…Three different deubiquitylating enzymes (DUBs) were also recently found to regulate mitophagy, with USP30 and USP15 opposing mitophagy by deubiquitylating parkin substrates (Bingol et al, 2014;Cornelissen et al, 2014), and USP8 promoting mitophagy by deubiquitylating parkin itself (Durcan et al, 2014). Another E3 ubiquitin ligase, Gp78 (also known as AMFR), also ubiquitylates mitofusin1 and mitofusin2 to induce mitophagy .…”

The Endosome-associated Deubiquitinating Enzyme USP8 Regulates BACE1 Enzyme Ubiquitination and Degradation

“…Currently, it is unknown whether USP8 deubiquitinates any other DUBs. However USP8 has been shown to deubiquitinate three E3 ligases, NRDP1 (48,49), GRAIL (50), and Parkin (27). Furthermore, USP8 depletion is known to result in decreased STAM and HRS protein levels (24,36).…”

“…Within the cell, USP8 has been found in the cytoplasm and at the endosome (23)(24)(25). USP8 degrades Lys-48-, Lys-63-, and Lys-6-linked ubiquitin chains (26,27). USP8 has been shown to negatively regulate the ubiquitination of lysosome-degraded proteins, including the epidermal growth factor receptor (EGFR) (23,28,29); tropomyosin-related kinase A (TRKA) (25); AMPA receptor (30); vascular endothelial growth factor receptor 2 (VEGFR2) (31); leucine-rich repeats and immunoglobulin-like domains 1 (LRIG1) (32); potassium intermediate/small conductance calcium-activated channel, subfamily N, member 4 (KCA3.1) (33); proteaseactivated receptor 2 (PAR2) (34); and ␦-opioid receptor (35).…”