Parkin and PINK1 mitigate STING-induced inflammation

Although serum from patients with Parkinson’s disease contains elevated levels of numerous pro-inflammatory cytokines including IL-6, TNF, IL-1β, and IFNγ, whether inflammation contributes to or is a consequence of neuronal loss remains unknown ¹ . Mutations in parkin, an E3 ubiquitin ligase, and PINK1, a ubiquitin kinase, cause early onset Parkinson’s disease ^2,3 . Both PINK1 and parkin function within the same biochemical pathway and remove damaged mitochondria from cells in culture and in animal models via mitophagy, a selective form of autophagy ⁴ . The in vivo role of mitophagy, however, is unclear, partly because mice that lack either PINK1 or parkin have no substantial Parkinson’s-disease-relevant phenotypes ^5–7 . Mitochondrial stress can lead to the release of damage-associated molecular patterns (DAMPs) that can activate innate immunity ^8–12 , suggesting that mitophagy may mitigate inflammation. Here we report a strong inflammatory phenotype in both Prkn ^−/− and Pink1 ^−/− mice following exhaustive exercise and in Prkn ^−/− ;mutator mice, which accumulate mutations in mitochondrial DNA (mtDNA) ^13,14 . Inflammation resulting from either exhaustive exercise or mtDNA mutation is completely rescued by concurrent loss of STING, a central regulator of the type I interferon response to cytosolic DNA ^15,16 . The loss of dopaminergic neurons from the substantia nigra pars compacta and the motor defect observed in aged Prkn ^−/− ;mutator mice are also rescued by loss of STING, suggesting that inflammation facilitates this phenotype. Humans with mono- and biallelic PRKN mutations also display elevated cytokines. These results support a role for PINK1- and parkin-mediated mitophagy in restraining innate immunity.