title: Characterization of the effect of the mitochondrial protein Hint2 on intracellular Ca(2+) dynamics.
abstract: Hint2, one of the five members of the superfamily of the histidine triad AMP-lysine hydrolase proteins, is expressed in mitochondria of various cell types. In human adrenocarcinoma cells, Hint2 modulates Ca(2+) handling by mitochondria. As Hint2 is highly expressed in hepatocytes, we investigated if this protein affects Ca(2+) dynamics in this cell type. We found that in hepatocytes isolated from Hint2(-/-) mice, the frequency of Ca(2+) oscillations induced by 1 μM noradrenaline was 150% higher than in the wild-type. Using spectrophotometry, we analyzed the rates of Ca(2+) pumping in suspensions of mitochondria prepared from hepatocytes of either wild-type or Hint2(-/-) mice; we found that Hint2 accelerates Ca(2+) pumping into mitochondria. We then resorted to computational modeling to elucidate the possible molecular target of Hint2 that could explain both observations. On the basis of a detailed model for mitochondrial metabolism proposed in another study, we identified the respiratory chain as the most probable target of Hint2. We then used the model to predict that the absence of Hint2 leads to a premature opening of the mitochondrial permeability transition pore in response to repetitive additions of Ca(2+) in suspensions of mitochondria. This prediction was then confirmed experimentally.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, Orsay, France.
authors.forename: Dieynaba
authors.initials: D
authors.lastname: Ndiaye
authors.forename: Mauricette
authors.initials: M
authors.lastname: Collado-Hilly
authors.forename: Juliette
authors.initials: J
authors.lastname: Martin
authors.forename: Sylvie
authors.initials: S
authors.lastname: Prigent
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Dufour
authors.forename: Laurent
authors.initials: L
authors.lastname: Combettes
authors.forename: Geneviève
authors.initials: G
authors.lastname: Dupont
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006867:Hydrolases / Q000172:deficiency / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D024101:Mitochondrial Proteins / Q000172:deficiency / Q000378:metabolism*; D008954:Models, Biological; D011487:Protein Conformation
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D024101:Mitochondrial Proteins; D006867:Hydrolases; C582071:HINT2 protein, mouse; D002118:Calcium