Regulation of Homocysteine-dependent Redox Homeostasis

描述（由申请人提供）：氧化应激引起的氧化还原稳态扰动似乎是连接各种复杂和多因素疾病病因的共同线索，如心血管疾病、帕金森病、阿尔茨海默病、关节炎和某些癌症。谷胱甘肽是真核生物细胞内抗氧化剂的关键组成部分，其合成的限制试剂被认为是半胱氨酸。将同型半胱氨酸转化为半胱氨酸的转硫途径是肝脏细胞内半胱氨酸库的重要定量贡献者，谷胱甘肽中- 50%的半胱氨酸是通过这一途径产生的。同型半胱氨酸是一种含硫氨基酸，其水平升高与许多多因素疾病有关，如心血管疾病、神经管缺陷和阿尔茨海默病。然而，这种氨基酸的细胞内调节以及与谷胱甘肽主要细胞氧化还原缓冲池的代谢联系尚不清楚。本研究的重点是调节同型半胱氨酸浓度的三个关键基因座：蛋氨酸合成酶、蛋氨酸合成酶还原酶和半胱氨酸-合成酶。这些酶的突变与遗传性高同型系统血症相关，这是一种常染色体隐性遗传病。结合生物物理，细胞生物学和小鼠模型研究半胱硫氨酸-合成酶缺乏症，我们将；(i)描述蛋氨酸合成酶还原酶的多态性变异和遗传突变如何影响蛋氨酸合成酶依赖的同型半胱氨酸转甲基化的氧化还原激活，（ii）阐明蛋氨酸合成酶的翻译调节机制，（iii）阐明氧化还原调节同型半胱氨酸代谢的机制及其对谷胱甘肽稳态的影响。这些研究将为同型半胱氨酸代谢的多个水平调控提供重要的见解，并将评估在细胞培养和小鼠中调节转硫途径对谷胱甘肽依赖的抗氧化防御的影响。

DESCRIPTION (provided by applicant): Perturbations of redox homeostasis incurred by oxidative stress appear to be a common thread connecting the etiologies of various complex and multifactorial diseases, such as cardiovascular diseases, Parkinson's disease, Alzheimer's disease, arthritis and some cancers. Glutathione is a key component of the intracellular arsenal of antioxidants in eukaryotes, and the limiting reagent in its synthesis is believed to cysteine. The transsulfuration pathway which converts homocysteine to cysteine is a quantitatively significant contributor to the intracellular cysteine pool in the liver and -50 percent of the cysteine in glutathione is derived via this pathway. Homocysteine is a sulfur containing amino acid whose elevated levels are correlated with a number of multifactorial diseases such as cardiovascular diseases, neural tube defects and Alzheimer's disease. However, intracellular regulation of this amino acid and of the metabolic link to the major cellular redox buffer pool of glutathione are poorly understood. This proposal focuses on three key loci important in regulation of homocysteine concentrations: methionine synthase, methionine synthase reductase and cystathionine beta-synthase. Mutations in each of these enzymes is correlated with hereditary hyperhomocystenemia which is inherited as an autosomal recessive disorder. Using a combination of biophysical, cell biological and mouse model studies for cystathionine beta-synthase deficiency, we will; (i) characterize how polymorphic variations and hereditary mutations in methionine synthase reductase influence redox activation of methionine synthase-dependent transmethyiation of homocysteine, (ii) elucidate the mechanism of translational regulation of methionine synthase and (iii) elucidate the mechanism of redox regulation of homocysteine metabolism and its influence on glutathione homeostasis. These studies will provide important insights into multiple levels of regulation of homocysteine metabolism and will assess the effects of modulating the transsulfuration pathway on glutathione-dependent antioxidant defense in cell culture and in mice.