title: Cystathionine is a novel substrate of cystine/glutamate transporter: implications for immune function.
abstract: The cystine/glutamate transporter, designated as system xc(-), is important for maintaining intracellular glutathione levels and extracellular redox balance. The substrate-specific component of system xc(-), xCT, is strongly induced by various stimuli, including oxidative stress, whereas it is constitutively expressed only in specific brain regions and immune tissues, such as the thymus and spleen. Although cystine and glutamate are the well established substrates of system xc(-) and the knockout of xCT leads to alterations of extracellular redox balance, nothing is known about other potential substrates. We thus performed a comparative metabolite analysis of tissues from xCT-deficient and wild-type mice using capillary electrophoresis time-of-flight mass spectrometry. Although most of the analyzed metabolites did not show significant alterations between xCT-deficient and wild-type mice, cystathionine emerged as being absent specifically in the thymus and spleen of xCT-deficient mice. No expression of either cystathionine β-synthase or cystathionine γ-lyase was observed in the thymus and spleen of mice. In embryonic fibroblasts derived from wild-type embryos, cystine uptake was significantly inhibited by cystathionine in a concentration-dependent manner. Wild-type cells showed an intracellular accumulation of cystathionine when incubated in cystathionine-containing buffer, which concomitantly stimulated an increased release of glutamate into the extracellular space. By contrast, none of these effects could be observed in xCT-deficient cells. Remarkably, unlike knock-out cells, wild-type cells could be rescued from cystine deprivation-induced cell death by cystathionine supplementation. We thus conclude that cystathionine is a novel physiological substrate of system xc(-) and that the accumulation of cystathionine in immune tissues is exclusively mediated by system xc(-).
authors.affiliation: From the Department of Food and Applied Life Sciences, Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan, the Department of Functional Genomics and Biotechnology, United Graduate School of Agricultural Sciences, Iwate University, Morioka, Iwate 020-8550, Japan, the Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Developmental Genetics, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany.
authors.forename: Sho
authors.initials: S
authors.lastname: Kobayashi
authors.affiliation: From the Department of Food and Applied Life Sciences, Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Sato
authors.affiliation: From the Department of Food and Applied Life Sciences, Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kasakoshi
authors.affiliation: From the Department of Food and Applied Life Sciences, Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Tsutsui
authors.affiliation: the Institute of Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sugimoto
authors.affiliation: the Division of Pathological Biochemistry, Tottori University Faculty of Medicine, Yonago 683-8503, Japan, the Chromosome Engineering Research Center, Tottori University, Yonago, 683-8503, Japan.
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Osaki
authors.affiliation: the Division of Pathological Biochemistry, Tottori University Faculty of Medicine, Yonago 683-8503, Japan, the Chromosome Engineering Research Center, Tottori University, Yonago, 683-8503, Japan.
authors.forename: Futoshi
authors.initials: F
authors.lastname: Okada
authors.affiliation: From the Department of Food and Applied Life Sciences, Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan.
authors.forename: Kiharu
authors.initials: K
authors.lastname: Igarashi
authors.affiliation: the Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Hiratake
authors.affiliation: the Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Yamagata 990-9585, Japan, and.
authors.forename: Takujiro
authors.initials: T
authors.lastname: Homma
authors.affiliation: the Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Developmental Genetics, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Conrad
authors.affiliation: the Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, Yamagata 990-9585, Japan, and.
authors.forename: Junichi
authors.initials: J
authors.lastname: Fujii
authors.affiliation: the Institute of Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052, Japan.
authors.forename: Tomoyoshi
authors.initials: T
authors.lastname: Soga
authors.affiliation: From the Department of Food and Applied Life Sciences, Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Bannai
authors.affiliation: From the Department of Food and Applied Life Sciences, Faculty of Agriculture, Yamagata University, Tsuruoka, Yamagata 997-8555, Japan, the Department of Functional Genomics and Biotechnology, United Graduate School of Agricultural Sciences, Iwate University, Morioka, Iwate 020-8550, Japan, the Laboratory of Biochemistry and Molecular Biology, Department of Medical Technology, Faculty of Medicine, Niigata University, Chuo-ku, Niigata 951-8518, Japan hideyo-s@clg.niigata-u.ac.jp.
authors.forename: Hideyo
authors.initials: H
authors.lastname: Sato
mesh_terms: D027182:Amino Acid Transport System y+; D000818:Animals; D001483:Base Sequence; D003540:Cystathionine / Q000378:metabolism*; D017931:DNA Primers; D007107:Immune System / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D027182:Amino Acid Transport System y+; D017931:DNA Primers; C492255:Slc7a11 protein, mouse; D003540:Cystathionine
keywords: Amino Acid Transport; Cystathionine; Cystine; Exchanger; Glutamate; Glutathione; Oxidative Stress; Substrate Specificity; System xc−