Protein kinase C-α inhibits the repair of oxidative phosphorylation after S-(1,2-dichlorovinyl)-L-cysteine injury in renal cells

Previously, we showed that physiological functions of renal proximal tubular cells (RPTC) do not recover following S-(1,2-dichlorovinyl)-L-cysteine (DCVC)-induced injury. This study investigated the role of protein kinase C-alpha (PKC-alpha) in the lack of repair of mitochondrial function in DCVC-injured RPTC. After DCVC exposure, basal oxygen consumption (QO(2)), uncoupled QO(2), oligomycin-sensitive QO(2), F1F0-ATPase activity, and ATP production decreased, respectively, to 59, 27, 27, 57, and 68% of controls. None of these functions recovered. Mitochondrial transmembrane potential decreased 53% after DCVC injury but recovered on day 4. PKC-alpha was activated 4.3- and 2.5-fold on days 2 and 4, respectively, of the recovery period. Inhibition of PKC-alpha activation (10 nM Go6976) did not block DCVC-induced decreases in mitochondrial functions but promoted the recovery of uncoupled QO2, oligomycin-sensitive QO(2), F1F0-ATPase activity, and ATP production. Protein levels of the catalytic beta-subunit of F1F0-ATPase were not changed by DCVC or during the recovery period. Amino acid sequence analysis revealed that alpha-, beta-, and is an element of-subunits of F1F0-ATPase have PKC consensus motifs. Recombinant PKC-alpha phosphorylated the beta-subunit and decreased F1F0-ATPase activity in vitro. Serine but not threonine phosphorylation of the beta-subunit was increased during late recovery following DCVC injury, and inhibition of PKC-alpha activation decreased this phosphorylation. We conclude that during RPTC recovery following DCVC injury, 1) PKC-alpha activation decreases F0F1-ATPase activity, oxidative phosphorylation, and ATP production; 2) PKC-alpha phosphorylates the beta-subunit of F1F0-ATPase on serine residue; and 3) PKC-alpha does not mediate depolarization of RPTC mitochondria. This is the first report showing that PKC-alpha phosphorylates the catalytic subunit of F1F0-ATPase and that PKC-alpha plays an important role in regulating repair of mitochondrial function.