Regulation of intermediary metabolism by the PKCδ signalosome in mitochondria

PKC delta has emerged as a novel regulatory molecule of oxidative phosphorylation by targeting the pyruvate dehydrogenase complex (PDHC). We showed that activation of PKC delta leads to the dephosphorylation of pyruvate dehydrogenase kinase 2 (PDK2), thereby decreasing PDK2 activity and increasing PDH activity, accelerating oxygen consumption, and augmenting ATP synthesis. However, the molecular components that mediate PKC delta signaling in mitochondria have remained elusive so far. Here, we identify for the first time a functional complex, which includes cytochrome c as the upstream driver of PKC delta, and uses the adapter protein p66Shc as a platform with vitamin A (retinol) as a fourth partner. All four components are necessary for the activation of the PKC delta signal chain. Genetic ablation of any one of the three proteins, or retinol depletion, silences signaling. Furthermore, mutations that disrupt the interaction of cytochrome c with p66Shc, of p66Shc with PKC delta, or the deletion of the retinol-binding pocket on PKC delta, attenuate signaling. In cytochrome c-deficient cells, reintroduction of cytochrome c Fe3+ protein restores PKC delta signaling. Taken together, these results indicate that oxidation of PKC delta is key to the activation of the pathway. The PKC delta/p66Shc/cytochrome c signalosome might have evolved to effect site-directed oxidation of zinc-finger structures of PKC delta, which harbor the activation centers and the vitamin A binding sites. Our findings define the molecular mechanisms underlying the signaling function of PKC delta in mitochondria.- Acin-Perez, R., Hoyos, B., Gong, J., Vinogradov, V., Fischman, D. A., Leitges, M., Borhan, B., Starkov, A., Manfredi, G., Hammerling, U. Regulation of intermediary metabolism by the PKC delta signalosome in mitochondria. FASEB J. 24, 5033-5042 (2010). www.fasebj.org