1. Identification of Bax-Interacting Proteins in Oligodendrocyte Progenitors during Glutamate Excitotoxicity and Perinatal Hypoxia–Ischemia
- Author
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Sopio Simonishvili, Teresa L. Wood, Hong Li, Steven W. Levison, and Mohit Jain
- Subjects
Time Factors ,IGF, insulin-like growth factor ,Excitotoxicity ,FGF-2, fibroblast growth factor-2 ,Kainate receptor ,Apoptosis ,medicine.disease_cause ,DMEM, Dulbecco’s modified Eagle’s medium ,tBid, truncated Bid ,0302 clinical medicine ,AF488, Alexa Fluor 488 ,Cerebellum ,Insulin-Like Growth Factor I ,MEM, minimal essential media ,Cells, Cultured ,AF546, Alexa Fluor 546 ,bcl-2-Associated X Protein ,0303 health sciences ,H–I, hypoxia–ischemia ,General Neuroscience ,Stem Cells ,Glutamate receptor ,IP, immunoprecipitation ,CCA, common carotid artery ,IL, ipsilateral ,Cell biology ,Mitochondria ,Oligodendroglia ,Protein Transport ,medicine.anatomical_structure ,VDAC, voltage-dependent anion channel ,Hypoxia-Ischemia, Brain ,Neurotoxicity Syndromes ,Research Article ,PIC, protease inhibitor cocktail ,Programmed cell death ,Glutamic Acid ,Bcl-xL ,AMPA receptor ,cofilin ,Biology ,S3 ,CNS, central nervous system ,S5 ,lcsh:RC321-571 ,Bid ,03 medical and health sciences ,Bcl-2-associated X protein ,FBS, fetal bovine serum ,medicine ,Animals ,Humans ,Rats, Wistar ,lcsh:Neurosciences. Biological psychiatry. Neuropsychiatry ,030304 developmental biology ,OPC, oligodendrocyte progenitor cell ,ACN, acetonitrile ,Oligodendrocyte ,Rats ,Disease Models, Animal ,stomatognathic diseases ,Animals, Newborn ,Gene Expression Regulation ,CL, contralateral ,Culture Media, Conditioned ,Immunology ,biology.protein ,Neurology (clinical) ,ADF, actin depolymerizing factor ,030217 neurology & neurosurgery ,insulin-like growth factor 1 (IGF-I) ,oligodendrocyte - 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.
- Published
- 2013