title: The Na+-dependent glutamate and aspartate transporter supports glutathione maintenance and survival of CHO-K1 cells.
abstract: Glutathione synthesis, a vital cellular process, depends on L-cystine uptake by the amino acid transporter, System x-C. Here we show that a second transporter, System X-AG, is required for normal System x-C activity and glutathione maintenance by employing somatic cell mutants of CHO-K1. Uptake by System x-C in two X-AG-null mutants is significantly lower than that of CHO-K1, either under control conditions or after prolonged treatment with an electrophile. In addition, levels of glutathione in control and treated mutant cells are less than half those of wild-type CHO-K1 or of a pseudorevertant. The significance of this reduction was tested by chemical challenge: mutants are twofold more sensitive than wild type to reactive oxygen species generated by phenylbenzoquinone and to damage produced by the anticancer drug, cisplatin. These results suggest that System X-AG provides a significant portion of the glutamate used to energize the uptake of cystine required for the synthesis of glutathione.
authors.affiliation: Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City 84132, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Igo
authors.forename: J F
authors.initials: JF
authors.lastname: Ash
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D016227:Benzoquinones / Q000494:pharmacology; D016466:CHO Cells; D002455:Cell Division / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002945:Cisplatin / Q000494:pharmacology; D006224:Cricetinae; D003470:Culture Media; D004351:Drug Resistance; D005838:Genotype; D018698:Glutamic Acid / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D005978:Glutathione / Q000096:biosynthesis / Q000378:metabolism* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D009154:Mutation / Q000235:genetics; D018384:Oxidative Stress; D012964:Sodium / Q000502:physiology*
chemical_list: D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D016227:Benzoquinones; D003470:Culture Media; D005973:Glutamine; D001224:Aspartic Acid; C029322:phenylbenzoquinone; D018698:Glutamic Acid; D012964:Sodium; D005978:Glutathione; D002945:Cisplatin