Cloning and Expression of a Plasma Membrane Cystine/Glutamate Exchange Transporter Composed of Two Distinct Proteins

Abstract

Transport system x c؊ found in plasma membrane of cultured mammalian cells is an exchange agency for anionic amino acids with high specificity for anionic form of cystine and glutamate. We have isolated cDNA encoding the transporter for system x c Ϫ from mouse activated macrophages by expression in Xenopus oocytes. The expression of system x c Ϫ activity in oocytes required two cDNA transcripts, and the sequence analysis revealed that one is identical with the heavy chain of 4F2 cell surface antigen (4F2hc) and the other is a novel protein of 502 amino acids with 12 putative transmembrane domains. The latter protein, named xCT, showed a significant homology with those recently reported to mediate cationic or zwitterionic amino acid transport when co-expressed with 4F2hc. Thus xCT is a new member of a family of amino acid transporters that form heteromultimeric complex with 4F2hc, with a striking difference in substrate specificity. The expression of system x c Ϫ was highly regulated, and Northern blot analysis demonstrated that the expression of both 4F2hc and xCT was enhanced in macrophages stimulated by lipopolysaccharide or an electrophilic agent. However, the expression of xCT was more directly correlated with the system x c Ϫ activity.

Relationship between [ 14 C]MeAIB uptake and amino acid transporter family gene expression levels or proliferative activity in a pilot study in human carcinoma cells: Comparison with [ 3 H]methionine uptake

“…Moreover, amino acids and amino acid transporters play important roles other than in energy metabolism, such as in macromolecular synthesis, mTOR activation, and ROS homeostasis beyond energy metabolism [49]. There are approximately fifty different types of amino acid transporters, but only LAT1 [50], LAT3 [51], ASCT2 [52], ATB 0, + [53] and xCT [54] have been reported to be expressed at high levels on the surface of cancer cells. Recently, there have been numerous reports in cancer cells related to glutamine transport via ASCT2 and LAT1 [55][56][57].…”

Modulation of multiple pathways involved in the maintenance of neuronal function during aging by fisetin

“…Cystine uptake in many types of cells is mediated by system X c -, a Na ? -independent cystine/ glutamate antiporter [78]. System X c -is a member of the disulfide-linked heteromeric amino acid transporter family and consists of a light chain (xCT) that confers substrate specificity and a heavy chain (4F2hc) that is shared among a number of different amino acid transporters.…”

Contribution of Cystine–Glutamate Antiporters to the Psychotomimetic Effects of Phencyclidine

“…This may reflect blunted cystine-glutamate exchange because cystine uptake into the cell represents the rate-limiting step in glutathione synthesis (Bannai, 1984;Meister, 1991;Sies, 1999). Alternatively, this could cause blunted cystine-glutamate exchange because extracellular glutathione metabolism serves as a reservoir for cystine that is critical in maintaining cystine-glutamate exchange (Deneke and Fanburg, 1989;Sato et al, 1999;Sies, 1999;Kim et al, 2001;Shih et al, 2006). Regardless, either would diminish glutamate release from cystine-glutamate exchange.…”