PINK1‐mediated mitophagy maintains pluripotency through optineurin

Objectives Dysfunction of autophagy results in accumulation of depolarized mitochondria and breakdown of self‐renewal and pluripotency in ESCs. However, the regulators that control how mitochondria are degraded by autophagy for pluripotency regulation remains largely unknown. This study aims to dissect the molecular mechanisms that regulate mitochondrial homeostasis for pluripotency regulation in mouse ESCs. Materials and methods Parkin+/+ and parkin −/− ESCs were established from E3.5 blastocysts of parkin+/− x parkin+/− mating mice. The pink1 −/−, optn −/− and ndp52 −/− ESCs were generated by CRISPR‐Cas9. shRNAs were used for function loss assay of target genes. Mito‐Keima, ROS and ATP detection were used to investigate the mitophagy and mitochondrial function. Western blot, Q‐PCR, AP staining and teratoma formation assay were performed to evaluate the PSC stemness. Results PINK1 or OPTN depletion impairs the degradation of dysfunctional mitochondria during reprogramming, and reduces the reprogramming efficiency and quality. In ESCs, PINK1 or OPTN deficiency leads to accumulation of dysfunctional mitochondria and compromised pluripotency. The defective mitochondrial homeostasis and pluripotency in pink1 −/− ESCs can be compensated by gain expression of phosphomimetic Ubiquitin (Ub‐S65D) together with WT or a constitutively active phosphomimetic OPTN mutant (S187D, S476D, S517D), rather than constitutively inactive OPTN (S187A, S476A, S517A) or a Ub‐binding dead OPTN mutant (D477N). Conclusions The mitophagy receptor OPTN guards ESC mitochondrial homeostasis and pluripotency by scavenging damaged mitochondria through TBK1‐activated OPTN binding of PINK1‐phosphorylated Ubiquitin.
Increasing reports show autophagy‐mediated mitochondrial homeostasis is essential for pluripotency regulation, but the receptors responsible for mitochondrial degradation in ESCs are unclear. Here, Wang et al identify OPTN is the mitochondrial autophagy receptor downstream of PINK1 that is responsible for regulation of mitochondrial homeostasis during both the acquisition and maintenance of pluripotency in a PARKIN‐independent manner.