Oxidative phosphorylation and mitochondrial dynamics are regulated by Sestrin2 to maintain cellular function

The stress-inducible protein Sestrin2 (SESN2) has recently emerged as an orchestrator of mitochondrial signaling. The regulation of mitochondria-related pathways, such as aerobic respiration, is thought to be mediated by SESN2, but the underlying mechanisms are not fully understood. Here, we characterized mitochondria in Sesn2-knockdown myoblasts under physiological conditions using oxygen consumption rate measurements, fluorescence microscopy, and protein content analysis. We discovered that SESN2 is essential for sustaining oxidative phosphorylation and maintaining the mitochondrial network organization. SESN2 loss diminished ATP production, decreased the levels of nuclear- and mitochondrial-encoded complex IV subunits, and increased superoxide generation. Moreover, the assessment of mitochondrial distribution in Sesn2-knockdown cells revealed a more fragmented network. This was associated with an increased ratio of short to long optic atrophy 1 (OPA1) forms. Remarkably, disruption of mitochondrial signaling suppressed cellular proliferation and altered both cell and nuclear morphology. In summary, our findings suggest that SESN2 plays an important role in maintaining cellular homeostasis, partly through its impact on mitochondrial function.