Mitochondrial double-stranded RNA drives aging-associated cognitive decline.

Aging is the primary cause of cognitive decline. Despite extensive study, the molecular mechanisms driving aging-associated cognitive decline remain unclear. Here, we describe a proteostasis-independent function of SEC61A1 and its involvement in aging-associated cognitive decline. SEC61A1 regulates ER-mitochondria contact sites, affecting mitochondrial DNA and RNA synthesis and subsequently leading to changes in innate immune signaling mediated by mitochondrial double-stranded RNA (mt-dsRNA). This pathway is activated in aged wild-type mice, Alzheimer's disease patients, and 5×FAD mice. Tissue-specific overexpression of Sec61a1 in the mouse cortex (Sec61a1(Tg)) is sufficient to induce cognitive decline without affecting motor activity. Knockdown of Sec61a1 or Mavs ablates mt-dsRNA-mediated innate immune signaling and alleviates cognitive decline in naturally aging wild-type mice. These results reveal a molecular mechanism of aging- and disease-associated cognitive decline and provide a potential therapeutic tool for intervention.