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-α (PKC-α) in the lack of repair of mitochondrial function in DCVC-injured RPTC. After DCVC exposure, basal oxygen consumption (Qo ₂), uncoupled Qo₂, oligomycin-sensitive Qo₂, 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-α was activated 4.3- and 2.5-fold on days 2 and 4, respectively, of the recovery period. Inhibition of PKC-α activation (10 nM Go6976) did not block DCVC-induced decreases in mitochondrial functions but promoted the recovery of uncoupled Qo₂, oligomycin-sensitive Qo₂, F₁F₀-ATPase activity, and ATP production. Protein levels of the catalytic β-subunit of F ₁F₀-ATPase were not changed by DCVC or during the recovery period. Amino acid sequence analysis revealed that α-, β-, and ε-subunits of F₁F₀-ATPase have PKC consensus motifs. Recombinant PKC-α phosphorylated the β-subunit and decreased F ₁F₀-ATPase activity in vitro. Serine but not threonine phosphorylation of the β-subunit was increased during late recovery following DCVC injury, and inhibition of PKC-α activation decreased this phosphorylation. We conclude that during RPTC recovery following DCVC injury, 1) PKC-α activation decreases F₁F₀-ATPase activity, oxidative phosphorylation, and ATP production; 2) PKC-α phosphorylates the β-subunit of F₁F₀-ATPase on serine residue; and 3) PKC-α does not mediate depolarization of RPTC mitochondria. This is the first report showing that PKC-α phosphorylates the catalytic subunit of F₁F₀-ATPase and that PKC-α plays an important role in regulating repair of mitochondrial function.