Genetic screening identifies integrated stress response kinase HRI (EIF2AK1) as a negative regulator of PINK1 and mitophagy signalling

Abstract

Loss of function mutations of the PINK1 kinase cause familial early-onset Parkinson’s disease. PINK1 is activated upon mitochondrial damage to phosphorylate Ubiquitin and Parkin to trigger removal of damaged mitochondria by autophagy (mitophagy). PINK1 also indirectly phosphorylates a subset of Rab GTPases including Rab8A. We have performed a siRNA screen of all human Ser/Thr kinases in HeLa cells and discovered the integrated stress response kinase EIF2AK1 (HRI) negatively regulates PINK1 following mitochondrial damage. We demonstrate that EIF2AK1 knockout cells enhance mitochondrial depolarization-induced stabilization of PINK1 and increased phosphorylation of Ubiquitin and Rab8A. We confirm our findings in multiple human cell lines including SK-OV-3, U2OS and ARPE-19 cells. Knockdown of upstream components of the recently described mitochondrial-cytosol relay pathway, OMA1 and DELE1, enhanced PINK1 stabilisation and activation similar to EIF2AK1. Using the mito-QC mitophagy reporter in human cells, we observe that EIF2AK1 knockdown moderately increases PINK1-dependent mitophagy. Our findings indicate that EIF2AK1 is a negative regulator of PINK1 and suggest that inhibitors of EIF2AK1 could have therapeutic benefits in Parkinson’s disease and related disorders of ageing and mitophagy