Abstract
Mitochondrial dysfunction has been implicated in aging, cardiovascular disease, cancer, neurodegeneration, and many other pathological conditions or diseases. The inner mitochondrial membrane (IMM) potential (a.k.a. ΔΨm) is essential for ATP synthesis via oxidative phosphorylation and also directly affects levels of reactive oxygen species, apoptosis, thermogenesis, and key signaling pathways. Better understanding the detailed mechanisms by which ΔΨm regulates cellular function and fate decisions requires tools to manipulate ΔΨm with spatial and temporal resolution, reversibility, or cell type specificity. To address this need, we have developed a new generation optogenetic-based technique for targeted mitochondrial depolarization with light. We demonstrate successful targeting of a heterologous Channelrhodopsin-2 (ChR2) fusion protein to the IMM and formation of functional cationic channels capable of light-induced targeted ΔΨm depolarization, which was sufficient to cause translocation of the cytosolic protein Parkin to mitochondria and activation of mitochondrial autophagy. Importantly, we show that optogenetic-mediated mitochondrial depolarization can be well-controlled to differentially influence the fate of cells expressing mitochondrial ChR2: while mild, transient light illumination elicits cytoprotective effect, moderate, sustained light illumination induces apoptotic cell death. This new generation optogenetic tool may be useful for studying the effects of ΔΨm depolarization on cell and organ function with spatial precision.