CASP9 and Parkinson disease: mPTP open causes CytC (cytochrome C) to be released outside mitochondria, then a cascade of cell apoptosis program, intermediated by CytC, Apaf-1 (apoptotic protease activating factor-1), caspase-3 and caspase-9, is triggered in neuronal cells, resulting in the pathogenesis of PD (Fig. 7).