Rajasekaran 2018 FASEB J
|Rajasekaran R, Felser A, Nuoffer JM, Dufour JF, St-Pierre MV (2018) The histidine triad nucleotide-binding protein 2 (HINT-2) positively regulates hepatocellular energy metabolism. FASEB J 32:5143-61.|
Abstract: The histidine triad nucleotide-binding protein 2 (HINT-2) is a mitochondrial adenosine phosphoramidase expressed in hepatocytes. The phenotype of Hint2 knockout (Hint2-/-) mice includes progressive hepatic steatosis and lysine hyperacetylation of mitochondrial proteins, which are features of respiratory chain malfunctions. We postulated that the absence of HINT-2 induces a defect in mitochondria bioenergetics. Isolated Hint2-/- hepatocytes produced less ATP and generated a lower mitochondrial membrane potential than did Hint2+/+ hepatocytes. In extracellular flux analyses with glucose, the basal, ATP-linked, and maximum oxygen consumption rates (OCRs) were decreased in Hint2-/- hepatocytes and in HepG2 cells lacking HINT-2. Conversely, in HINT-2 overexpressing SNU-449 and HepG2 cells, the basal, ATP-linked, and maximum OCRs were increased. Similarly, with palmitate, basal and maximum OCRs were decreased in Hint2-/- hepatocytes, but they were increased in HINT-2 overexpressing HepG2 cells. When assayed with radiolabeled substrate, palmitate oxidation was reduced by 25% in Hint2-/- mitochondria. In respirometry assays, complex I- and II-driven, coupled and uncoupled respirations and complex IV KCN-sensitive respiration were reduced in Hint2-/- mitochondria. Furthermore, HINT-2 associated with cardiolipin and glucose-regulated protein 75 kDa. Our study shows decreased electron transfer and oxidative phosphorylation capacity in the absence of HINT-2. The bioenergetics deficit accumulated over time in hepatocytes lacking HINT-2 likely leads to the secondary outcome of steatosis.
Labels: MiParea: Respiration, Genetic knockout;overexpression
Organism: Mouse Tissue;cell: Liver Preparation: Isolated mitochondria
Coupling state: LEAK, OXPHOS, ET Pathway: N, S, CIV, ROX HRR: Oxygraph-2k