Tom70 serves as a molecular switch to determine pathological cardiac hypertrophy.

Pathological cardiac hypertrophy is an inevitable forerunner of heart failure. Regardless of the etiology of cardiac hypertrophy, cardiomyocyte mitochondrial alterations are always observed in this context. The translocases of mitochondrial outer membrane (Tom) complex governs the import of mitochondrial precursor proteins to maintain mitochondrial function under pathophysiological conditions; however, its role in the development of pathological cardiac hypertrophy remains unclear. Here, we showed that Tom70 was downregulated in pathological hypertrophic hearts from humans and experimental animals. The reduction in Tom70 expression produced distinct pathological cardiomyocyte hypertrophy both in vivo and in vitro. The defective mitochondrial import of Tom70-targeted optic atrophy-1 triggered intracellular oxidative stress, which led to a pathological cellular response. Importantly, increased Tom70 levels provided cardiomyocytes with full resistance to diverse pro-hypertrophic insults. Together, these results reveal that Tom70 acts as a molecular switch that orchestrates hypertrophic stresses and mitochondrial responses to determine pathological cardiac hypertrophy.