Cystine-dependent antiporters buffer against excess intracellular reactive sulfur species-induced stress
Masahiro Akiyama,
Takamitsu Unoki,
Hanako Aoki,
Akiyuki Nishimura,
Yasuhiro Shinkai,
Eiji Warabi,
Kazuhiro Nishiyama,
Yuka Furumoto,
Naohiko Anzai,
Takaaki Akaike,
Motohiro Nishida,
Yoshito Kumagai
Affiliations
Masahiro Akiyama
Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan; Faculty of Pharmacy and Graduate School of Pharmaceutical Science, Keio University, Tokyo, 105-8512, Japan
Takamitsu Unoki
Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan; Department of Basic Medical Sciences, National Institute for Minamata Disease, Kumamoto, 867-0008, Japan
Hanako Aoki
Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, 305-8575, Japan
Akiyuki Nishimura
National Institute for Physiological Sciences, National Institutes of Natural Sciences, Aichi, 444-8787, Japan
Yasuhiro Shinkai
Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan; Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, 305-8575, Japan
Eiji Warabi
Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan; Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, 305-8575, Japan
Kazuhiro Nishiyama
Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582, Japan
Yuka Furumoto
Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582, Japan
Naohiko Anzai
Graduate School of Medicine, Chiba University, Chiba, 260-8670, Japan
Takaaki Akaike
Graduate School of Medicine, Tohoku University, Miyagi, 980-8575, Japan
Motohiro Nishida
National Institute for Physiological Sciences, National Institutes of Natural Sciences, Aichi, 444-8787, Japan; Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, 812-8582, Japan
Yoshito Kumagai
Faculty of Medicine, University of Tsukuba, Ibaraki, 305-8575, Japan; Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, 305-8575, Japan; Corresponding author. Environmental Biology Laboratory, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
Reactive sulfur species (RSS) play a role in redox homeostasis; however, adaptive cell responses to excessive intracellular RSS are not well understood. Therefore, in this study, we generated transgenic (Tg) mice overexpressing cystathionine gamma-lyase (CSE) to produce excessive RSS. Contrary to expectations, tissue concentrations of RSS, such as cysteine persulfide (CysSSH), were comparable in both wild-type and CSE Tg mice, but the plasma concentrations of CysSSH were significantly higher in CSE Tg mice than in wild-type mice. This export of surplus intracellular RSS was also observed in primary hepatocytes of CSE Tg mice. Exposure of primary hepatocytes to the RSS generator sodium tetrasulfide (Na2S4) resulted in an initial increase in the intracellular concentration of RSS, which later returned to basal levels after export into the extracellular space. Interestingly, among all amino acids, cystine (CysSSCys) was found to be essential for CysSSH export from primary mouse hepatocytes, HepG2 cells, and HEK293 cells during Na2S4 exposure, suggesting that the cystine/glutamate transporter (SLC7A11) contributes, at least partially, to CysSSH export. We established HepG2 cell lines with knockout and overexpression of SLC7A11 and used them to confirm SLC7A11 as the predominant antiporter of CysSSCys and CysSSH. We observed that the poor efflux of excess CysSSH from the cell enhanced cellular stresses induced by Na2S4 exposure, such as polysulfidation of intracellular proteins, mitochondrial damage, and cytotoxicity. These results suggest the presence of a cellular response to excess intracellular RSS that involves the extracellular efflux of excess CysSSH by a cystine-dependent transporter to maintain intracellular redox homeostasis.
