Abstract 205: Overexpression of the Mitochondrial FoF1 ATP Synthase regulators ATP12 and ATP5J are Protective against Ischemia-Reperfusion Injury in the Heart

Loss of cardiomyocytes by necrotic cell death is a substantial underlying problem in progressive heart failure. One crucial step that is required for regulated necrosis to ensue is the opening of the mitochondrial permeability transition pore (MPTP), which is triggered by elevations in mitochondrial matrix calcium and reactive oxygen species levels. Opening of the MPTP causes permeabilization of the inner mitochondrial membrane and collapse of the electrochemical proton gradient required for ATP production. The latest model of the MPTP consists of the F o F 1 ATP synthase as the pore forming component within the inner mitochondrial membrane, although the mechanistic aspects of how the ATP synthase generates the pore is unknown. Two regulators of the ATP synthase, ATP12 and ATP5J, were identified in an unbiased calcium overload necrotic cell death screen using a lenti-viral gain-of-function library containing over 13,000 human cDNAs. ATP12 is an assembly factor of the F 1 component of the ATP synthase where it directly binds to the α-subunit and prevents homo-oligomerization. ATP5J is a component of the peripheral stalk that links the F o and F 1 portions of the ATP synthase together. To test if overexpression of ATP12 or ATP5J is indeed protective as we identified in the screen, here we generated cardiac-specific transgenic mice expressing each of these proteins. When subjected to ischemia-reperfusion injury, both ATP5J and ATP12 overexpressing mice were significantly protected. Additionally, mitochondria isolated from the overexpressing hearts demonstrated increased mitochondrial calcium uptake, a hallmark of MPTP desensitization. These data provide evidence that ATP12 and ATP5J are novel inhibitors of MPTP opening through their association with the F o F 1 ATP synthase and thus protect against necrotic cell death.