Akt activation improves oxidative phosphorylation in renal proximal tubular cells following nephrotoxicant injury.
Previously, we showed that protein kinase B (Akt) activation increases intracellular ATP levels and decreases necrosis in renal proximal tubular cells (RPTC) injured by the nephrotoxicant S-(1, 2-dichlorovinyl)-l-cysteine (DCVC) (Shaik ZP, Fifer EK, Nowak G. Am J Physiol Renal Physiol 292: F292-F303, 2007). This study examined the role of Akt in improving mitochondrial function in DCVC-injured RPTC. Our data show a novel observation that phosphorylated (active) Akt is localized in mitochondria of noninjured RPTC, both in mitoplasts and the mitochondrial outer membrane. Mitochondrial levels of active Akt decreased in nephrotoxicant-injured RPTC, and this decrease was associated with mitochondrial dysfunction. DCVC decreased basal, uncoupled, and state 3 respirations; ATP production; activities of complexes I, II, and III; the mitochondrial membrane potential (DeltaPsi(m)); and F(0)F(1)-ATPase activity. Expressing constitutively active Akt in DCVC-injured RPTC increased the levels of phosphorylated Akt in mitochondria, reduced the decreases in basal and uncoupled respirations, increased complex I-coupled state 3 respiration and ATP production, enhanced activities of complex I, complex III, and F(0)F(1)-ATPase, and improved DeltaPsi(m). In contrast, inhibiting Akt activation by expressing dominant negative (inactive) Akt or using 20 microM LY294002 exacerbated decreases in electron transport rate, state 3 respiration, ATP production, DeltaPsi(m), and activities of complex I, complex III, and F(0)F(1)-ATPase. In conclusion, our data show that Akt activation promotes mitochondrial respiration and ATP production in toxicant-injured RPTC by 1) improving integrity of the respiratory chain and maintaining activities of complex I and complex III, 2) reducing decreases in DeltaPsi(m), and 3) restoring F(0)F(1)-ATPase activity.
Shaik
Zabeena P
ZP
Department of Pharmaceutical Sciences, College of Pharmacy, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA.
Fifer
E Kim
EK
Nowak
Grazyna
G
D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D003545:Cysteine / Q000031:analogs & derivatives / Q000633:toxicity; D004579:Electron Transport / Q000187:drug effects / Q000502:physiology; D042967:Electron Transport Complex I / Q000187:drug effects / Q000378:metabolism; D042963:Electron Transport Complex II / Q000187:drug effects / Q000378:metabolism; D014450:Electron Transport Complex III / Q000187:drug effects / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000187:drug effects / Q000378:metabolism; D004785:Environmental Pollutants / Q000633:toxicity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007674:Kidney Diseases / Q000139:chemically induced / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000378:metabolism / Q000503:physiopathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D051336:Mitochondrial Membranes / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009840:Oligomycins / Q000494:pharmacology; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D014162:Transfection
D002867:Chromones; D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; D009025:Morpholines; D009840:Oligomycins; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C039961:S-(1,2-dichlorovinyl)cysteine; D000255:Adenosine Triphosphate; D042963:Electron Transport Complex II; D003576:Electron Transport Complex IV; D051057:Proto-Oncogene Proteins c-akt; D006180:Proton-Translocating ATPases; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III; D003545:Cysteine