Dehydroepiandrosterone-induced changes in mitochondrial proteins contribute to phenotypic alterations in hepatoma...

Dehydroepiandrosterone (DHEA)-induced growth arrest of hepatoma cells is associated with metabolic disturbance. Our previous study has suggested that DHEA may cause cellular energy drain. It is possible that mitochondrial dysfunction may be mechanistically implicated in DHEA-induced changes in cellular phenotype. Treatment of SK-Hep-1 cells with DHEA caused significant reduction in proliferation, colony formation, and growth in semi-solid medium. Such changes in cellular phenotype were associated with mitochondrial depolarization, increase in mitochondrial mass, and decrease in respiratory activity. Level of reactive oxygen species (ROS) increased in DHEA-treated cells. To explore the mechanistic aspect of DHEA-induced mitochondrial dysfunction, we employed SILAC approach to study the changes in the mitoproteome of SK-Hep-1 cells after DHEA treatment. Respiratory chain complex proteins such as NDUFB8 and SDHB were differentially expressed. Of mitochondrial proteins with altered expression, FAST kinase domain-containing protein 2 (FASTKD2) showed significantly reduced expression. Exogenous expression of FASTKD2 in SK-Hep-1 cells increased their resistance to growth-inhibitory effect of DHEA, though it alone did not affect cell growth. FASTKD2 expression partially reversed the effect of DHEA on mitochondria, and reduced DHEA-induced ROS generation. Our results suggest that DHEA induces changes in mitochondrial proteins and respiratory activity, and contributes to growth arrest. FASTKD2 may be an important regulator of mitochondrial physiology, and represent a downstream target for DHEA.