Gravitational and mechanical forces shape mitochondrial translation

Life on Earth has evolved in a form suitable for the gravitational force of 1 × g. Although the pivotal role of gravity in gene expression has been revealed by multiomics approaches in space-flown samples and astronauts, the molecular details of how mammalian cells harness gravity have remained unclear. Here, we show that mitochondria utilize gravity to activate protein synthesis within the organelle. Genome-wide ribosome profiling unveiled reduced mitochondrial translation in mammalian cells and Caenorhabditis elegans under microgravity in the International Space Station and under simulated microgravity in the 3D-clinostat on the ground. In addition, we found that cell adhesion through laminin–integrin interaction, which is attenuated by microgravity, and the downstream FAK, RAC1, PAK1, BAD, and Bcl-2 family proteins relay the signals for mitochondrial protein synthesis. Consistent with the role of integrin as a mechanosensor, we observed the decrease in mitochondrial translation by minimization of mechanical stress in mouse skeletal muscle. Our work provides mechanistic insights into how cells convert gravitational and mechanical forces into translation in an energy-producing organelle.