PINK1 and Parkinson disease: The PINK1 protein is largely known for its role in mitochondrial quality control.10,11 PINK1 is a kinase that is stabilized on the outer mitochondrial membrane when the mitochondrion loses its membrane potential, initiating a pathway resulting in mitophagy.12 The lack of functional PINK1 in familial forms of PD was thus thought to promote the accumulation of dysfunctional mitochondria causing dopaminergic neuronal death; however, this has proven difficult to validate.