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.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Surgery, Anesthesiology and Trauma Study Section (SAT)
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Hoshizaki, Deborah K
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University of Arkansas for Medical Sciences
Schools of Pharmacy
Little Rock
United States
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Nowak, Grazyna; Bakajsova-Takacsova, Diana (2018) Protein kinase C? targets respiratory chain and mitochondrial membrane potential but not F0 F1 -ATPase in renal cells injured by oxidant. J Cell Biochem 119:9394-9407
Nowak, Grazyna; Takacsova-Bakajsova, Diana; Megyesi, Judit (2017) Deletion of protein kinase C-? attenuates mitochondrial dysfunction and ameliorates ischemic renal injury. Am J Physiol Renal Physiol 312:F109-F120
Nowak, Gra?yna; Bakajsova, Diana (2015) Protein kinase C-? interaction with F0F1-ATPase promotes F0F1-ATPase activity and reduces energy deficits in injured renal cells. J Biol Chem 290:7054-66
Nowak, Gra?yna; Bakajsova, Diana (2013) Assessment of mitochondrial functions and cell viability in renal cells overexpressing protein kinase C isozymes. J Vis Exp :
Nowak, Grazyna; Soundararajan, Sridharan; Mestril, Ruben (2013) Protein kinase C-? interaction with iHSP70 in mitochondria promotes recovery of mitochondrial function after injury in renal proximal tubular cells. Am J Physiol Renal Physiol 305:F764-76
Nowak, Grazyna; Bakajsova, Diana (2012) Protein kinase C-? activation promotes recovery of mitochondrial function and cell survival following oxidant injury in renal cells. Am J Physiol Renal Physiol 303:F515-26
Nowak, Grazyna; Bakajsova, Diana; Hayes, Corey et al. (2012) ?-Tocotrienol protects against mitochondrial dysfunction and renal cell death. J Pharmacol Exp Ther 340:330-8
Nowak, Grazyna; Bakajsova, Diana; Samarel, Allen M (2011) Protein kinase C-epsilon activation induces mitochondrial dysfunction and fragmentation in renal proximal tubules. Am J Physiol Renal Physiol 301:F197-208
Nowak, Grazyna; Clifton, Ginger L; Bakajsova, Diana (2008) Succinate ameliorates energy deficits and prevents dysfunction of complex I in injured renal proximal tubular cells. J Pharmacol Exp Ther 324:1155-62
Shaik, Zabeena P; Fifer, E Kim; Nowak, Grazyna (2008) Akt activation improves oxidative phosphorylation in renal proximal tubular cells following nephrotoxicant injury. Am J Physiol Renal Physiol 294:F423-32

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