OPA1 and ischemia: In the current study, we provide evidence that, in HL-1 cardiomyocytes, simulated ischemia-reperfusion injury is accompanied by increased OMA1 protease activity, the proteolytic processing of mitochondrial OPA1 from L-OPA1 to S-OPA1 isoforms, and redistribution of S-OPA1 from mitochondria to the cytosol following reoxygenation.