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Cell surface expression of system x c − is upregulated in non‐confluent cell cultures
Author(s) -
Sherburn Stephanie,
Condelee Mazi,
Goltz Abby,
Chase Leah A.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.698.8
Subject(s) - glutathione , intracellular , extracellular , microbiology and biotechnology , cell membrane , transporter , cell culture , cell , cysteine , chemistry , biochemistry , biology , enzyme , genetics , gene
System x c − is a transport system that exchanges extracellular cystine for intracellular glutamate. The transporter plays an important role in providing cysteine as a precursor for glutathione synthesis and in maintaining the redox balance within the cell. We recently reported that oxidants regulate the activity of System x c − by altering the rate of trafficking of the transporter to the plasma membrane. Additionally, we have demonstrated that cell surface expression of System x c − is influence by cell culture density. Using cell surface biotinylation assays, we showed that only 35‐45% of the transporter is localized to the plasma membrane in confluent cultures of human glioma cells, while 90% of the transporter is localized to the membrane in cultures which are only 50% confluent. In this study, we tested the hypothesis that the difference in membrane localization of System x c − is a result of a greater glutathione demand in actively dividing non‐confluent cells compared to confluent cells which are no longer actively dividing. We used enzymatic assays and immunotcytochemical methods to measure the glutathione levels in confluent and non‐confluent cultures of human glioma cells. These studies reported here combined with our previous studies suggest that the localization of System x c − is influenced by the glutathione levels in the cells independent of the mechanism by which gluathione levels are modulated.