Translational control of inducible nitric oxide synthase expression by arginine can explain the arginine paradox
Translational control of inducible nitric oxide synthase expression by arginine can explain the arginine paradox
复制标题
DOI：
10.1073/pnas.0735876100
复制
发表时间：
2003-04-15
影响因子：
11.1
通讯作者：
Ratan, RR
中科院分区：
文献类型：
--
作者：
Lee, J;Ryu, H;Ratan, RR
l -精氨酸是NO合成酶（NOS）唯一的内源性含氮底物，因此它在神经系统发育过程中以及中风、多发性硬化症、帕金森病和HIV痴呆等疾病状态下控制NO的产生。“精氨酸悖论”指的是尽管细胞内的l -精氨酸在理论上饱和了NOS酶，但细胞内NO的产生依赖于外源的l -精氨酸浓度。本文中，我们报道了l -精氨酸可用性的降低，通过抑制可诱导的NOS （iNOS）蛋白表达，阻断了细胞因子刺激的星形胶质细胞中NO生成的诱导。但NOS基因启动子的活性、NOS mRNA的诱导和NOS蛋白的稳定性均未受到抑制。我们的研究结果表明，在受刺激的星形胶质细胞培养中，精氨酸消耗对NOS活性的抑制是通过抑制iNOS mRNA的翻译来实现的。在细胞因子的刺激下，l -精氨酸的摄取负向调节真核起始因子（eIF2alpha）的磷酸化状态，进而调节NOS mRNA的翻译。eIF2alpha的磷酸化与酵母GCN2 eIF2alpha激酶的哺乳动物同源物的磷酸化相关。由于GCN2的激酶活性通过磷酸化激活，这些发现表明GCN2活性代表了l -精氨酸可用性对MOS翻译调节的近端步骤。这些结果为NOS的精氨酸悖论提供了解释，并定义了一种底物调节其相关酶活性的独特机制。
L-Arginine is the only endogenous nitrogen-containing substrate of NO synthase (NOS), and it thus governs the production of NO during nervous system development as well as in disease states such as stroke, multiple sclerosis, Parkinson's disease, and HIV dementia. The "arginine paradox" refers to the dependence of cellular NO production on exogenous L-arginine concentration despite the theoretical saturation of NOS enzymes with intracellular L-arginine. Herein, we report that decreased availability of L-arginine blocked induction of NO production in cytokine-stimulated astrocytes, owing to inhibition of inducible NOS (iNOS) protein expression. However, activity of the promoter of the NOS gene, induction of NOS mRNA, and stability of NOS protein were not inhibited under these conditions. Our results indicate that inhibition of NOS activity by arginine depletion in stimulated astrocyte cultures occurs via inhibition of translation of iNOS mRNA. After stimulation by cytokines, uptake of L-arginine negatively regulates the phosphorylation status of the eukaryotic initiation factor (eIF2alpha), which, in turn, regulates translation of NOS mRNA. eIF2alpha phosphorylation correlates with phosphorylation of the mammalian homolog of yeast GCN2 eIF2alpha kinase. As the kinase activity of GCN2 is activated by phosphorylation, these findings suggest that GCN2 activity represents a proximal step in the MOS translational regulation by availability of L-arginine. These results provide an explanation for the arginine paradox for NOS and define a distinct mechanism by which a substrate can regulate the activity of its associated enzyme.