Lysine 63-linked Polyubiquitination Is Dispensable for Parkin-mediated Mitophagy

PINK1/Parkin-mediated mitophagy is thought to ensure mitochondrial quality control in neurons as well as other cells. Upon the loss of mitochondrial membrane potential (Delta Psi m), Lys-63-linked polyubiquitin chains accumulate on the mitochondrial outer membrane in a Parkin-dependent manner. However, the physiological significance of Lys-63-linked polyubiquitination during mitophagy is not fully understood. Here, we report that the suppression of Lys-63-linked polyubiquitination through the removal of Ubc13 activity essentially affects neither PINK1 activation nor the degradation of depolarized mitochondria. Moreover, the inactivation of Ubc13 did not modulate the mitochondrial phenotypes of PINK1 knockdown Drosophila. Our data indicate that the formation of Lys-63-linked polyubiquitin chains on depolarized mitochondria is not a key factor for the PINK1-Parkin pathway as was once thought.