The long-term goal of our research is to elucidate the signaling events and regulatory mechanisms involved in: 1) the loss of renal functions associated with acute renal failure (ARF) as caused by ischemia/reperfusion and 2) the repair of renal functions following ARF. The kidney is one of the major target organs for ischemia/reperfusion and oxidative stress-induced damage. Renal proximal tubular cells (RPTC) are a major target of these insults within the kidney due to their dependence on mitochondrial function and oxygen for energy (ATP) generation and large capacity for biotransformation of xenobiotics. Protein kinase signaling is emerging as a major mechanism regulating mitochondrial function. The goal of this proposal is to determine signaling mechanisms through which two protein kinase C isozymes (PKC-??and PKC-?) regulate mitochondrial dysfunction, oxidative stress, and cell survival during injury and repair of RPTC following hypoxia. Our recent studies demonstrated a key role of two isoforms of PKC in regulating mitochondrial functions during repair of injured RPTC. Our preliminary data demonstrate the novel observation that PKC-?, PKC-??are present in RPTC mitochondria and that PKC phosphorylates a number of yet unidentified mitochondrial proteins. We demonstrated that PKC-??activation mediates mitochondrial dysfunction following injury. Inhibition of PKC-??activation promotes recovery of mitochondrial function, diminishes energy deficits, and decreases RPTC necrosis following hypoxia and oxidant-induced injury. In contrast, the activation of PKC-??reduces mitochondrial dysfunction and RPTC necrosis following hypoxia and oxidant-induced injury. The central hypothesis of this proposal is that PKC-??and PKC-??differentially regulate ATP synthesis by phosphorylating key proteins of mitochondrial oxidative phosphorylation apparatus and/or the mitochondrial permeability transition pore. The following specific aims will test this hypothesis. Specific Aim 1 will determine the specific mitochondrial pathways of energy metabolism that are regulated by PKC-??and PKC-??during RPTC injury and repair. Specific Aim 2 will identify proteins through which PKC-??and PKC- ??regulate mitochondrial energy metabolism in injured RPTC. Specific Aim 3 will determine whether PKC-??and/or PKC-??regulate mitochondrial respiration and ATP production in ischemic kidney and whether protein complexes involved in oxidative phosphorylation are mitochondrial targets for PKC-??and/or PKC-??in the kidney in vivo. Upon completion of this project, we will have important novel information that will help us understand the significance of PKC-??and PKC-??in kidney repair following injury and will provide insights into using these kinases as targets for new therapeutic interventions to treat renal failure. PUBLIC HEALTH RELEVANCE: Current therapies to treat injury caused by ischemia (reduced availability of oxygen) in the kidney and other organs are limited because the mechanisms that regulate renal injury and recovery are not well understood. This project will examine how three different enzymes (protein kinases) regulate production of energy in the injured kidney and the recovery of the kidney from injury caused by ischemia. Therefore, upon completion of this project we will have an important novel information that will help us understand the significance of these kinases in renal repair and will provide insights into the possibility of using these kinases as targets for new therapies against renal failure.