Mitochondrial quality control and dynamics in Parkinson's disease.

Significance: Studies of sporadic cases, toxin models, and genetic causes of Parkinson's disease suggest that mitochondrial dysfunction may be an early feature of pathogenesis.

Recent Advances: Compelling evidence of a causal relationship between mitochondrial function and disease was found with the identification of several genes for recessive parkinsonism, PINK1, DJ-1, and parkin. There is evidence that each of these regulates responses to cellular stresses, including oxidative stress and depolarization of the mitochondrial membrane. Specifically, PINK1 and parkin modulate mitochondrial dynamics by promoting autophagic removal of depolarized mitochondria. Mutations in all genes linked to Parkinson's disease lead to enhanced sensitivity to mitochondrial toxins and oxidative stress.

Critical Issues: Both increased mitochondrial damage due to complex 1 inhibition, mishandling of calcium, oxidant stress, or impaired clearance of dysfunctional mitochondria would lead to the accumulation of nonfunctional organelles and could contribute to neuronal dysfunction. However, several unanswered questions remain about the underlying mechanism(s) involved.

Future Directions: PINK1 and parkin have been demonstrated to regulate mitochondrial dynamics, but the pathways linking PINK1 activity to parkin function are still unclear and warrant further investigation.