Optogenetically engineered Ca²⁺ oscillation-mediated DRP1 activation promotes mitochondrial fission and cell death

Mitochondrial dynamics regulate the quality and morphology of mitochondria. Calcium (Ca²⁺) plays an important role in regulating mitochondrial function. Here, we investigated the effects of optogenetically engineered Ca²⁺ signaling on mitochondrial dynamics. More specifically, customized illumination conditions could trigger unique Ca²⁺ oscillation waves to trigger specific signaling pathways. In this study, we found that modulating Ca²⁺ oscillations by increasing the light frequency, intensity and exposure time could drive mitochondria toward the fission state, mitochondrial dysfunction, autophagy and cell death. Moreover, illumination triggered phosphorylation at the Ser616 residue but not the Ser637 residue of the mitochondrial fission protein, dynamin-related protein 1 (DRP1, encoded by DNM1L), via the activation of Ca²⁺-dependent kinases CaMKII, ERK and CDK1. However, optogenetically engineered Ca²⁺ signaling did not activate calcineurin phosphatase to dephosphorylate DRP1 at Ser637. In addition, light illumination had no effect on the expression levels of the mitochondrial fusion proteins mitofusin 1 (MFN1) and 2 (MFN2). Overall, this study provides an effective and innovative approach to altering Ca²⁺ signaling for controlling mitochondrial fission with a more precise resolution than pharmacological approaches in the temporal dimension.