title: Identification of Bax-interacting proteins in oligodendrocyte progenitors during glutamate excitotoxicity and perinatal hypoxia-ischemia.
abstract: OPC (oligodendrocyte progenitor cell) death contributes significantly to the pathology and functional deficits following hypoxic-ischemic injury in the immature brain and to deficits resulting from demyelinating diseases, trauma and degenerative disorders in the adult CNS. Glutamate toxicity is a major cause of oligodendroglial death in diverse CNS disorders, and previous studies have demonstrated that AMPA/kainate receptors require the pro-apoptotic protein Bax in OPCs undergoing apoptosis. The goal of the present study was to define the pro-apoptotic and anti-apoptotic effectors that regulate Bax in healthy OPCs and after exposure to excess glutamate in vitro and following H-I (hypoxia-ischemia) in the immature rat brain. We show that Bax associates with a truncated form of Bid, a BH3-only domain protein, subsequent to glutamate treatment. Furthermore, glutamate exposure reduces Bax association with the anti-apoptotic Bcl family member, Bcl-xL. Cell fractionation studies demonstrated that both Bax and Bid translocate from the cytoplasm to mitochondria during the early stages of cell death consistent with a role for Bid as an activator, whereas Bcl-xL, which normally complexes with both Bax and Bid, disassociates from these complexes when OPCs are exposed to excess glutamate. Bax remained unactivated in the presence of insulin-like growth factor-1, and the Bcl-xL complexes were protected. Our data similarly demonstrate loss of Bcl-xL-Bax association in white matter following H-I and implicate active Bad in Bax-mediated OPC death. To identify other Bax-binding partners, we used proteomics and identified cofilin as a Bax-associated protein in OPCs. Cofilin and Bax associated in healthy OPCs, whereas the Bax-cofilin association was disrupted during glutamate-induced OPC apoptosis.
authors.affiliation: *Department of Neurology & Neuroscience, New Jersey Medical School Cancer Center, Rutgers Biomedical & Health Sciences, Newark, NJ 07101, U.S.A.
authors.forename: Sopio
authors.initials: S
authors.lastname: Simonishvili
authors.affiliation: †Center for Advanced Proteomic Research and Department of Biochemistry and Molecular Biology, New Jersey Medical School Cancer Center, Rutgers Biomedical & Health Sciences, Newark, NJ 07101, U.S.A.
authors.forename: Mohit Raja
authors.initials: MR
authors.lastname: Jain
authors.affiliation: †Center for Advanced Proteomic Research and Department of Biochemistry and Molecular Biology, New Jersey Medical School Cancer Center, Rutgers Biomedical & Health Sciences, Newark, NJ 07101, U.S.A.
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.affiliation: *Department of Neurology & Neuroscience, New Jersey Medical School Cancer Center, Rutgers Biomedical & Health Sciences, Newark, NJ 07101, U.S.A.
authors.forename: Steven W
authors.initials: SW
authors.lastname: Levison
authors.affiliation: *Department of Neurology & Neuroscience, New Jersey Medical School Cancer Center, Rutgers Biomedical & Health Sciences, Newark, NJ 07101, U.S.A.
authors.forename: Teresa L
authors.initials: TL
authors.lastname: Wood
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D018698:Glutamic Acid / Q000633:toxicity; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D020258:Neurotoxicity Syndromes / Q000209:etiology / Q000473:pathology*; D009836:Oligodendroglia / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: D017077:Culture Media, Conditioned; D051028:bcl-2-Associated X Protein; D018698:Glutamic Acid; D007334:Insulin-Like Growth Factor I