Role of Selenium in Cancer and Health

硒在癌症和健康中的作用

• 批准号: 7038499
• 负责人: Dolph Hatfield
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7038499
• 关键词: Drosophilidae; RNA interference; breast neoplasms; cancer prevention; chemoprevention; cysteine; dietary mineral; gene targeting; genetic promoter element; genetically modified animals; laboratory mouse; nutrition aspect of cancer; nutrition related tag; pathologic process; protein structure function; selenated sulfur aminoacid; selenium; selenoprotein; tissue /cell culture; transfer RNA

Selenium has a role in preventing various forms of cancer (e.g., colon, prostate, lung and liver), heart disease and other cardiovascular and muscle disorders. It also serves as an antiviral agent and plays a role in delaying the aging process, in delaying the progression of AIDS in HIV positive patients, in immune function, in mammalian development and in male reproduction. Although the underlying metabolic effects of selenium are poorly understood, they are due, at least in part, to the presence of this element in selenoproteins as the amino acid, selenocysteine (Sec). Our program focuses on the means by which Sec is incorporated into protein and the role of specific selenoproteins in human health and development. In the last year, we discovered the gene for an important enzyme in Sec biosynthesis and characterized its product, phosphoseryl-tRNASerSec kinase (PSTK). In addition, we are using RNAi to knock down several selenoproteins and other proteins involved in Sec biosynthesis (e.g., SLA, PSTK, SPS1 and 2) to further elucidate their roles in selenium metabolism and determine how this element is incorporated into protein. Since Sec tRNA is the only known tRNA that governs the expression of an entire class of proteins, the selenoproteins, we have perturbed Sec tRNA synthesis to better understand the role of selenium and selenoproteins in health. Over the last few years, we have generated transgenic, knockout, conditional knockout and knockdown cells and mice involving the Sec tRNA gene to provide models for explicating the role of selenoproteins in health and development. We rescued standard Sec tRNA gene knockout mice that are embryonic lethal with transgenic mice carrying either a wild type or mutant Sec tRNA transgene and analyzed which selenoproteins are rescued. The mutant Sec tRNA is incapable of forming a methyl group at the 2'-O-hydroxy position on the ribose in position 34 which is the last step in the maturation of Sec tRNA. Mice rescued with the wild type transgene expressed all selenoproteins normally, but mice rescued with the mutant transgene did not express several stress-related selenoproteins, but expressed housekeeping selenoproteins in normal or reduced amounts. This novel regulation of protein expression occurred at the level of translation and manifested a tissue-specific pattern. The data indicate that Sec tRNA methylation at the 2'-O-hydroxylribosyl site plays a role in regulating the expression of various mammalian selenoproteins and is required for synthesis of non-essential, stress-related selenoproteins. Using loxP-Cre technology, we mated the conditional knockout mice with different Cre mice to selectively remove the Sec tRNA gene (and therefore alter selenoprotein expression) in various tissues including liver, prostate, breast, endothelial cells and skeletal and heart muscle. In this way, we can assess the role of selenoproteins in development, in tissue and organ function and in health. This past year we have knocked out selenoprotein expression in endothelial cells and heart and skeletal muscle. Animals lacking selenoprotein expression in endothelial cells died after 14.5 days dpc from multiple abnormalities, while those animals lacking selenoprotein expression in heart and skeletal muscle died abruptly at about 10 days after birth from heart disease. The latter studies clearly show that selenoproteins are involved in the development and normal function of endothelial cells and heart muscle. The conditional knockout of Sec tRNA in specifically targeted tissues and organs provides an excellent model for examining the role of selenoproteins in development and health.

硒在预防各种形式的癌症（例如结肠，前列腺，肺和肝脏），心脏病以及其他心血管疾病和肌肉疾病中起作用。它也充当抗病毒剂，并在延迟衰老过程，延迟艾滋病毒阳性患者的艾滋病进展，免疫功能，哺乳动物发育和男性繁殖方面发挥作用。尽管硒的潜在代谢作用知之甚少，但它们至少部分归因于硒蛋白中该元素作为氨基酸，硒代半胱氨酸（SEC）的存在。我们的计划着重于将SEC纳入蛋白质以及特定硒蛋白在人类健康和发育中的作用的手段。在去年，我们发现了Sec生物合成中重要酶的基因，并将其产物磷酸磷酸盐酶（PSTK）进行了表征。此外，我们正在使用RNAi击倒参与SEC生物合成的几种硒蛋白和其他蛋白质（例如SLA，PSTK，SPS1和2），以进一步阐明其在硒代谢中的作用，并确定该元素如何掺入蛋白质中。由于SEC tRNA是控制整个蛋白质（硒蛋白）表达的唯一已知tRNA，因此我们已经扰动SEC tRNA合成，以更好地了解硒和硒蛋白在健康中的作用。在过去的几年中，我们产生了转基因，敲除，有条件的敲除和敲除细胞以及涉及SEC TRNA基因的小鼠，以提供阐明硒蛋白在健康和发育中的作用的模型。我们挽救了标准的SEC tRNA基因基因敲除小鼠，这些小鼠具有胚胎致死的小鼠，转基因小鼠携带野生型或突变体SEC tRNA转基因并分析了硒蛋白被拯救。突变的SEC tRNA无法在核糖上的2'-O-羟基位置形成甲基34位的甲基，这是SEC TRNA成熟的最后一步。用野生型转基因救出的小鼠通常表达了所有硒蛋白，但是用突变体转基因救出的小鼠没有表达几种与压力相关的硒蛋白，而是以正常或减少的量表示家政硒蛋白。这种新型蛋白质表达的调节发生在翻译水平，并表现出组织特异性的模式。数据表明，在2'-O-羟基甲基甲基位点的SEC tRNA甲基化在调节各种哺乳动物硒蛋白的表达中起作用，并且是合成非必需的，与应激相关的硒蛋白所必需的。使用LOXP-CRE技术，我们与不同的CRE小鼠配对了条件敲除小鼠，以选择性地去除肝脏，前列腺，乳腺，内皮细胞以及骨骼和心肌在内的各种组织中的SEC tRNA基因（因此改变硒蛋白的表达）。这样，我们可以评估硒蛋白在发育，组织和器官功能以及健康中的作用。在过去的一年中，我们淘汰了内皮细胞以及心脏和骨骼肌中的硒蛋白表达。在多种异常的14.5天DPC后，内皮细胞中缺乏硒蛋白表达的动物死亡，而那些缺乏心脏和骨骼肌中缺乏硒蛋白表达的动物在出生后大约10天因心脏病而突然死亡。后一项研究清楚地表明，硒蛋白参与内皮细胞和心肌的发育和正常功能。特定靶向组织和器官中SEC tRNA的条件敲除，为检查硒蛋白在发育和健康中的作用提供了一个极好的模型。