Reduced protein kinase C delta in a high molecular weight complex in mitochondria and elevated creatine uptake into Barth syndrome B lymphoblasts

Barth syndrome (BTHS) is a rare X-linked genetic disease in which mitochondrial oxidative phosphorylation is impaired due to a mutation in the TAFAZZIN gene. The protein kinase C delta (PKCδ) signalosome exists as a high molecular weight complex in mitochondria and controls mitochondrial oxidative phosphorylation. Method: Here, we examined PKCδ levels in mitochondria of aged-matched control and BTHS patient B lymphoblasts and its association with a higher molecular weight complex in mitochondria. Result: Immunoblot analysis of blue-native polyacrylamide gel electrophoresis mitochondrial fractions revealed an increase in total PKCδ protein expression in BTHS lymphoblasts compared to controls. In contrast, PKCδ associated with a higher molecular weight complex was markedly reduced in BTHS patient B lymphoblasts compared to controls. Given the decrease in PKCδ associated with a higher molecular weight complex in mitochondria, we examined the uptake of creatine, a compound whose utilization is enhanced upon high energy demand. Creatine uptake was markedly elevated in BTHS lymphoblasts compared to controls.

We hypothesize that reduced PKCδ within this higher molecular weight complex in mitochondria may contribute to the bioenergetic defects observed in BTHS lymphoblasts and that enhanced creatine uptake may serve as one of several compensatory mechanisms for the defective mitochondrial oxidative phosphorylation observed in these cells.