Department of Pathology, UT Southwestern Medical Center, Dallas, TX, 75390-9072, USA.
Children's Medical Center Research Institute, UT Southwestern Medical Center, Dallas, TX, 75390, USA.
Cell Mol Life Sci. 2021 Jan;78(1):195-206. doi: 10.1007/s00018-020-03483-1. Epub 2020 Feb 22.
Hypoxia-inducible factors (HIFs) mediate metabolic reprogramming in response to hypoxia. However, the role of HIFs in branched-chain amino acid (BCAA) metabolism remains unknown. Here we show that hypoxia upregulates mRNA and protein levels of the BCAA transporter LAT1 and the BCAA metabolic enzyme BCAT1, but not their paralogs LAT2-4 and BCAT2, in human glioblastoma (GBM) cell lines as well as primary GBM cells. Hypoxia-induced LAT1 protein upregulation is mediated by both HIF-1 and HIF-2 in GBM cells. Although both HIF-1α and HIF-2α directly bind to the hypoxia response element at the first intron of the human BCAT1 gene, HIF-1α is exclusively responsible for hypoxia-induced BCAT1 expression in GBM cells. Knockout of HIF-1α and HIF-2α significantly reduces glutamate labeling from BCAAs in GBM cells under hypoxia, which provides functional evidence for HIF-mediated reprogramming of BCAA metabolism. Genetic or pharmacological inhibition of BCAT1 inhibits GBM cell growth under hypoxia. Together, these findings uncover a previously unrecognized HIF-dependent metabolic pathway that increases GBM cell growth under conditions of hypoxic stress.
缺氧诱导因子 (HIFs) 介导代谢重编程以应对缺氧。然而，HIF 在支链氨基酸 (BCAA) 代谢中的作用尚不清楚。在这里，我们表明，在人胶质母细胞瘤 (GBM) 细胞系以及原代 GBM 细胞中，缺氧上调了 BCAA 转运体 LAT1 和 BCAA 代谢酶 BCAT1 的 mRNA 和蛋白水平，但不上调其旁系同源物 LAT2-4 和 BCAT2。GBM 细胞中，缺氧诱导的 LAT1 蛋白上调由 HIF-1 和 HIF-2 介导。虽然 HIF-1α 和 HIF-2α 均可直接结合人 BCAT1 基因第一内含子中的缺氧反应元件，但 HIF-1α 是 GBM 细胞中缺氧诱导 BCAT1 表达的唯一因子。敲除 HIF-1α 和 HIF-2α 可显著减少 GBM 细胞在缺氧条件下从 BCAA 中标记的谷氨酸，这为 HIF 介导的 BCAA 代谢重编程提供了功能证据。BCAT1 的遗传或药理学抑制可抑制 GBM 细胞在缺氧下的生长。总之，这些发现揭示了一种以前未被识别的 HIF 依赖性代谢途径，该途径可在缺氧应激条件下增加 GBM 细胞的生长。
