Institute for Research in Biomedicine (IRB Barcelona), The Barcelona Institute of Science and Technology, Barcelona, 08028, Spain.
Department of Cell Biology, Physiology and Immunology, Faculty of Biology, Universitat de Barcelona, Barcelona, 08028, Spain.
Sci Rep. 2019 Oct 1;9(1):14065. doi: 10.1038/s41598-019-50547-9.
CD98 heavy chain (CD98hc) forms heteromeric amino acid (AA) transporters by interacting with different light chains. Cancer cells overexpress CD98hc-transporters in order to meet their increased nutritional and antioxidant demands, since they provide branched-chain AA (BCAA) and aromatic AA (AAA) availability while protecting cells from oxidative stress. Here we show that BCAA and AAA shortage phenocopies the inhibition of mTORC1 signalling, protein synthesis and cell proliferation caused by CD98hc ablation. Furthermore, our data indicate that CD98hc sustains glucose uptake and glycolysis, and, as a consequence, the pentose phosphate pathway (PPP). Thus, loss of CD98hc triggers a dramatic reduction in the nucleotide pool, which leads to replicative stress in these cells, as evidenced by the enhanced DNA Damage Response (DDR), S-phase delay and diminished rate of mitosis, all recovered by nucleoside supplementation. In addition, proper BCAA and AAA availability sustains the expression of the enzyme ribonucleotide reductase. In this regard, BCAA and AAA shortage results in decreased content of deoxynucleotides that triggers replicative stress, also recovered by nucleoside supplementation. On the basis of our findings, we conclude that CD98hc plays a central role in AA and glucose cellular nutrition, redox homeostasis and nucleotide availability, all key for cell proliferation.
CD98 重链(CD98hc)通过与不同的轻链相互作用形成异源氨基酸(AA)转运体。癌细胞过度表达 CD98hc-转运体,以满足其增加的营养和抗氧化需求,因为它们提供支链氨基酸(BCAA)和芳香族氨基酸(AAA)的可用性,同时保护细胞免受氧化应激。在这里,我们表明,BCAA 和 AAA 缺乏可模拟 CD98hc 缺失引起的 mTORC1 信号转导、蛋白质合成和细胞增殖的抑制。此外,我们的数据表明,CD98hc 维持葡萄糖摄取和糖酵解,因此维持戊糖磷酸途径(PPP)。因此,CD98hc 的缺失会导致核苷酸池的急剧减少,这会导致这些细胞中的复制应激,如增强的 DNA 损伤反应(DDR)、S 期延迟和有丝分裂率降低所证明的那样,所有这些都可以通过核苷补充来恢复。此外,适当的 BCAA 和 AAA 可用性维持酶核糖核苷酸还原酶的表达。在这方面,BCAA 和 AAA 缺乏会导致脱氧核苷酸含量降低,从而引发复制应激,核苷补充也可恢复这一应激。基于我们的发现,我们得出结论,CD98hc 在 AA 和葡萄糖细胞营养、氧化还原平衡和核苷酸可用性方面发挥着核心作用,所有这些都是细胞增殖的关键。