PINK1

PINK1 (PTEN-induced kinase 1) is a mitochondrial serine/threonine kinase that functions as a sensor of mitochondrial damage and a central regulator of mitochondrial quality control mechanisms.^[1] Upon mitochondrial depolarization, PINK1 accumulates on the outer mitochondrial membrane rather than undergoing constitutive turnover, thereby marking dysfunctional mitochondria for selective removal.^[2][3] Mechanistically, stabilized PINK1 phosphorylates both ubiquitin and the E3 ubiquitin ligase Parkin, initiating a ubiquitin-dependent mitophagy pathway that promotes recruitment of autophagic machinery to damaged mitochondria.^[3][4] Through this PINK1-Parkin signaling axis, cells maintain mitochondrial homeostasis, limit accumulation of dysfunctional organelles, and support neuronal survival under cellular stress conditions.^[1][3][5] The PINK1-mediated mitophagy pathway is strongly linked to neurodegenerative disease biology, particularly Parkinson’s disease, where mutations in PINK1 represent an established cause of autosomal recessive early-onset Parkinsonism.^[6][7] Experimental studies further demonstrate that impaired PINK1-Parkin signaling results in defective mitochondrial clearance and accumulation of damaged mitochondria, whereas restoration of pathway activity promotes mitophagy and protects neurons from apoptosis in disease models.^[5][8] Compared with related mitochondrial quality-control regulators, PINK1 is distinguished by its kinase-dependent damage-sensing function and its highly specific phosphorylation of ubiquitin, a critical upstream event required for efficient Parkin activation.^[4] For experimental applications, genetic modulation of PINK1 expression and pharmacological enhancement of PINK1-Parkin-mediated mitophagy are widely used to investigate mitochondrial dysfunction, neurodegeneration, and mitochondrial quality-control mechanisms.^[5][9]