CHCHD2 and CHCHD10 regulate mitochondrial dynamics and integrated stress response

Mitochondrial dysfunction is becoming one of the main pathology factors involved in the etiology of neurological disorders. Recently, mutations of the coiled-coil-helix-coiled-coil-helix domain containing 2 (CHCHD2) and 10 (CHCHD10) which encode two homologous proteins that belong to the mitochondrial CHCH domain protein family, are linked to Parkinson's disease and amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD), respectively. However, the physiological and pathological roles of these twin proteins have not been well elaborated. Here, we show that, in physiological conditions, CHCHD2 and CHCHD10 interact with OMA1 and suppress its enzyme activity, which not only restrains the initiation of the mitochondrial integrated response stress (mtISR), but also suppresses the processing of OPA1 for mitochondrial fusion. Further, during mitochondria stress-induced by carbonyl cyanide m-chlorophenylhydrazone (CCCP) treatment, CHCHD2 and CHCHD10 translocate to the cytosol and interacte with eIF2a, which attenuates mtISR overactivation by suppressing eIF2a phosphorylation and its downstream response. As such, knockdown of CHCHD2 and CHCHD10 triggers mitochondrial ISR, and such cellular response is enhanced by CCCP treatment. Therefore, our findings demonstrate the first "mtISR suppressor" localized in mitochondria for regulating stress responses in mammalian cells, which has a profound pathological impact on the CHCH2/CHCH10-linked neurodegenerative disorder.