title: A cystine-cysteine shuttle mediated by xCT facilitates cellular responses to S-nitrosoalbumin.
abstract: We have shown previously that extracellular cysteine is necessary for cellular responses to S-nitrosoalbumin. In this study we have investigated mechanisms involved in accumulation of extracellular cysteine outside vascular smooth muscle cells and characterized the role of cystine-cysteine release in transfer of nitric oxide (NO)-bioactivity. Incubation of cells with cystine led to cystine uptake, reduction, and cysteine release. The process was inhibitable by extracellular glutamate, suggesting a role for system x(c)(-) amino acid transporters. Smooth muscle cells express this transporter constitutively and induction of the light chain component (xCT) by either diethyl maleate or 3-morpholino-sydnonimine (SIN-1) led to glutamate-inhibitable cystine uptake and an increased rate of cysteine release from cells. Likewise, overexpression of xCT in smooth muscle cells or endothelial cells led to glutamate-inhibitable cysteine release. The resulting extracellular cysteine was found to be required for transfer of NO from extracellular S-nitrosothiols into cells via system L transporters leading to formation of cellular S-nitrosothiols. Cysteine release coupled to cystine uptake was also found to be required for cellular responses to S-nitrosoalbumin and facilitated S-nitrosoalbumin-mediated inhibition of epidermal growth factor signaling. These data show that xCT expression can constitute a cystine-cysteine shuttle whereby cystine uptake drives cysteine release. Furthermore, we show that extracellular cysteine provided by this shuttle mechanism is necessary for transfer of NO equivalents and cellular responses to S-nitrosoablumin.
authors.affiliation: Department of Pharmacology & Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhu
authors.forename: Sheng
authors.initials: S
authors.lastname: Li
authors.forename: Zermeena M
authors.initials: ZM
authors.lastname: Marshall
authors.forename: A R
authors.initials: AR
authors.lastname: Whorton
mesh_terms: D027182:Amino Acid Transport System y+ / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D003545:Cysteine / Q000378:metabolism*; D003553:Cystine / Q000378:metabolism*; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009603:Nitroso Compounds / Q000494:pharmacology*; D051381:Rats; D012710:Serum Albumin, Bovine / Q000494:pharmacology*
chemical_list: D027182:Amino Acid Transport System y+; D009603:Nitroso Compounds; C091665:S-nitrosoalbumin; C118895:SLC7A11 protein, human; D012710:Serum Albumin, Bovine; D003553:Cystine; D003545:Cysteine