PINK1 Loss of Function Selectively Alters the Mitochondrial-Derived Vesicle Pathway

Abstract

Cell homeostasis and metabolic control require the efficient function of mitochondria and implementation of quality control pathways following damage. Cells have various discrete pathways of mitochondrial quality control (mitoQC) to maintain the healthy network. PINK1 and Parkin are two key players in mitoQC, most highly associated with the ubiquitin-dependent capture and degradation of whole mitochondria by autophagy. However, these proteins have alternative roles in repair routes directing locally damaged cargo to the lysosome, such as the mitochondrial-derived vesicle (MDV) pathway. We aimed to clarify the role of PINK1 and determine how its loss of function impacts mitochondrial dynamics and quality control. Results indicate PINK1 knockout (KO) has little impact on whole mitochondrial turnover in response to damage in SH-SY5Y cells, whereas both PINK1 and Parkin KO cells have healthy mitochondrial networks with efficient ATP production. However, TOM20 positive outer-membrane and damage-induced PDH-positive inner-membrane MDVs are elevated in PINK1 KO cells. Although, in contrast to Parkin KO, this is not due to a defect in trafficking to a LAMP1-positive compartment and may instead indicate increased damage-induced flux. In comparison, loss of Atg5-dependent mitophagy has no effect on whole mitochondrial turnover and only results in a limited elevation in inner-membrane MDVs in response to damage, indicating autophagy-independent mechanisms of whole mitochondrial turnover and a minor compensatory increase in damage-induced MDVs. Therefore, these data suggest PINK1 and Parkin are dispensable for whole mitochondrial turnover, but following their perturbation have disparate effects on the MDV pathway.