PMID- 32265299 OWN - NLM STAT- MEDLINE DCOM- 20201223 LR - 20210516 IS - 1083-351X (Electronic) IS - 0021-9258 (Print) IS - 0021-9258 (Linking) VI - 295 IP - 20 DP - 2020 May 15 TI - High cell density increases glioblastoma cell viability under glucose deprivation via degradation of the cystine/glutamate transporter xCT (SLC7A11). PG - 6936-6945 LID - 10.1074/jbc.RA119.012213 [doi] AB - The cystine/glutamate transporter system x(c)(-) consists of the light-chain subunit xCT (SLC7A11) and the heavy-chain subunit CD98 (4F2hc or SLC3A2) and exchanges extracellular cystine for intracellular glutamate at the plasma membrane. The imported cystine is reduced to cysteine and used for synthesis of GSH, one of the most important antioxidants in cancer cells. Because cancer cells have increased levels of reactive oxygen species, xCT, responsible for cystine-glutamate exchange, is overexpressed in many cancers, including glioblastoma. However, under glucose-limited conditions, xCT overexpression induces reactive oxygen species accumulation and cell death. Here we report that cell survival under glucose deprivation depends on cell density. We found that high cell density (HD) down-regulates xCT levels and increases cell viability under glucose deprivation. We also found that growth of glioblastoma cells at HD inactivates mTOR and that treatment of cells grown at low density with the mTOR inhibitor Torin 1 down-regulates xCT and inhibits glucose deprivation-induced cell death. The lysosome inhibitor bafilomycin A1 suppressed xCT down-regulation in HD-cultured glioblastoma cells and in Torin 1-treated cells grown at low density. Additionally, bafilomycin A1 exposure or ectopic xCT expression restored glucose deprivation-induced cell death at HD. These results suggest that HD inactivates mTOR and promotes lysosomal degradation of xCT, leading to improved glioblastoma cell viability under glucose-limited conditions. Our findings provide evidence that control of xCT protein expression via lysosomal degradation is an important mechanism for metabolic adaptation in glioblastoma cells. CI - (c) 2020 Yamaguchi et al. FAU - Yamaguchi, Itsuki AU - Yamaguchi I AD - Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. FAU - Yoshimura, Shige H AU - Yoshimura SH AD - Laboratory of Plasma Membrane and Nuclear Signaling, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan. FAU - Katoh, Hironori AU - Katoh H AUID- ORCID: 0000-0002-8191-8117 AD - Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan hirokato@pharm.kyoto-u.ac.jp. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20200407 PL - United States TA - J Biol Chem JT - The Journal of biological chemistry JID - 2985121R RN - 0 (Amino Acid Transport System y+) RN - 0 (Neoplasm Proteins) RN - 0 (SLC7A11 protein, human) RN - IY9XDZ35W2 (Glucose) SB - IM MH - Amino Acid Transport System y+/genetics/*metabolism MH - Cell Line, Tumor MH - Glioblastoma/genetics/*metabolism/pathology MH - Glucose/*metabolism MH - Humans MH - Neoplasm Proteins/genetics/*metabolism MH - *Proteolysis PMC - PMC7242691 OTO - NOTNLM OT - amino acid transport OT - cancer biology OT - cell biology OT - cell death OT - lysosome COIS- The authors declare that they have no conflicts of interest with the contents of this article EDAT- 2020/04/09 06:00 MHDA- 2020/12/29 06:00 PMCR- 2021/05/15 CRDT- 2020/04/09 06:00 PHST- 2019/12/06 00:00 [received] PHST- 2020/03/25 00:00 [revised] PHST- 2020/04/09 06:00 [pubmed] PHST- 2020/12/29 06:00 [medline] PHST- 2020/04/09 06:00 [entrez] PHST- 2021/05/15 00:00 [pmc-release] AID - S0021-9258(17)48197-X [pii] AID - RA119.012213 [pii] AID - 10.1074/jbc.RA119.012213 [doi] PST - ppublish SO - J Biol Chem. 2020 May 15;295(20):6936-6945. doi: 10.1074/jbc.RA119.012213. Epub 2020 Apr 7.