title: Possible involvement of mitochondrial uncoupling protein-2 in cytotoxicity mediated by acquired N-methyl-D-aspartate receptor channels.
abstract: We have previously shown the possible involvement of mitochondrial membrane potential disruption in the mechanisms underlying the neurotoxicity seen after activation of N-methyl-d-aspartate (NMDA) receptors (NMDAR) in primary cultured rat hippocampal neurons. In this study, we attempted to demonstrate a pivotal role of mitochondrial uncoupling protein-2 (UCP2) as a determinant of the NMDA neurotoxicity by using acquired NMDAR channels artificially orchestrated in HEK293 cells. In cells with overexpression of UCP2, immunoreactive UCP2 was exclusively detected at intracellular locations stained with the mitochondrial marker MitoTracker. In cells with acquired NMDAR channels, exposure to either NMDA or the calcium ionophore A23187 similarly led to a significant increase in cytosolic Ca(2+) levels determined by Fluo-3 imaging irrespective of the overexpression of UCP2. By contrast, NMDA, but not A23187, was significantly more effective in increasing mitochondrial Ca(2+) levels determined by Rhod-2 fluorescence imaging in cells transfected with NMDAR subunit and UCP2 expression vectors than in those without UCP2 overexpression. Overexpression of UCP2 significantly increased the number of cells stained with propidium iodide in cultures with acquired NMDAR channels, but failed to significantly affect that in cells exposed to A23187. Immunocytochemical and immunoprecipitation analyses similarly revealed the possible interaction between GluN1 subunit and UCP2 in HEK293 cells with acquired NMDAR channels and UCP2 overexpression. These results suggest that UCP2 could play a role as a determinant of the neurotoxicity mediated by NMDAR through a mechanism related to the unidentified interaction with the essential GluN1 subunit toward modulation of mitochondrial Ca(2+) levels in neurons.
authors.affiliation: Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa 920-1192, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Fukumori
authors.forename: Takeshi
authors.initials: T
authors.lastname: Takarada
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kambe
authors.forename: Ryota
authors.initials: R
authors.lastname: Nakazato
authors.forename: Koichi
authors.initials: K
authors.lastname: Fujikawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Yoneda
mesh_terms: D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007150:Immunohistochemistry; D007473:Ion Channels / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D000071246:Uncoupling Protein 2
chemical_list: D007473:Ion Channels; D024101:Mitochondrial Proteins; D016194:Receptors, N-Methyl-D-Aspartate; C000604389:UCP2 protein, human; C000604391:Ucp2 protein, rat; D000071246:Uncoupling Protein 2; D000001:Calcimycin; D002118:Calcium