Dalgard Clifton Lee, Lu Huasheng, Mohyeldin Ahmed, Verma Ajay
Department of Neurology, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
Biochem J. 2004 Jun 1;380(Pt 2):419-24. doi: 10.1042/BJ20031647.
Adaptations to change in oxygen availability are crucial for survival of multi-cellular organisms and are also implicated in several disease states. Such adaptations rely upon gene expression regulated by the heterodimeric transcription factors HIFs (hypoxia-inducible factors). Enzymes that link changes in oxygen tensions with the stability and transcriptional activity of HIFs are considered as oxygen sensors. These enzymes are oxygen-, iron- and 2-oxoglutarate-dependent dioxygenases that hydroxylate key proline and asparagine residues in HIFalpha subunits. The constitutive inhibitory action of these enzymes on HIFs is relieved by hypoxia and by agents that displace iron or 2-oxoglutarate. Two of the enzymes, HPH (HIF prolyl hydroxylase)-1 and HPH-2, are known to be inducible by hypoxia in a HIF-dependent manner. This suggests the existence of a novel feedback loop for adjusting hypoxia-regulated gene expression. We have recently shown that HIF-1alpha stability, HIF-1 nuclear translocation and HIF-mediated gene expression in human glioma cell lines can be stimulated by pyruvate independently of hypoxia. In the present study we show that the endogenous 2-oxoacid oxaloacetate can also activate HIF-mediated gene expression. Pyruvate and oxaloacetate treatment of cells also up-regulates HPH-1 and HPH-2, but not HPH-3 or the HIF asparaginyl hydroxylase FIH-1 (factor inhibiting HIF). Regulation of HIF-1 and the expression of HPH homologue genes can thus be influenced by specific glycolytic and tricarboxylic acid cycle metabolites. These findings may underlie important interactions between oxygen homoeostasis, glycolysis, the tricarboxylic acid cycle and gluconeogenesis.
适应氧气供应变化对于多细胞生物的生存至关重要，并且与多种疾病状态也有关联。此类适应依赖于由异二聚体转录因子HIFs（缺氧诱导因子）调控的基因表达。将氧张力变化与HIFs的稳定性和转录活性联系起来的酶被视为氧传感器。这些酶是依赖氧、铁和2-氧代戊二酸的双加氧酶，可将HIFα亚基中的关键脯氨酸和天冬酰胺残基羟基化。这些酶对HIFs的组成性抑制作用可通过缺氧以及置换铁或2-氧代戊二酸的试剂而解除。已知其中两种酶，即HPH（HIF脯氨酰羟化酶）-1和HPH-2，可被缺氧以HIF依赖的方式诱导。这表明存在一种用于调节缺氧调控基因表达的新型反馈回路。我们最近发现，丙酮酸可独立于缺氧刺激人胶质瘤细胞系中的HIF-1α稳定性、HIF-1核转位及HIF介导的基因表达。在本研究中，我们表明内源性2-氧代酸草酰乙酸也可激活HIF介导的基因表达。用丙酮酸和草酰乙酸处理细胞还会上调HPH-1和HPH-2，但不会上调HPH-3或HIF天冬酰胺酰羟化酶FIH-1（HIF抑制因子）。因此，特定的糖酵解和三羧酸循环代谢产物可影响HIF-1及HPH同源基因的表达。这些发现可能是氧稳态、糖酵解、三羧酸循环和糖异生之间重要相互作用的基础。
