Methionine sulfoxide reduction, selenium and aging

描述（由申请方提供）：甲硫氨酸亚砜（Met（O））还原是一种重要的代谢途径，可提供抗氧化应激保护并调节蛋白质功能。Met（O）在活性氧存在下形成，并被肽Met（O）还原酶还原回甲硫氨酸。一种Met（O）还原酶（MsrA）已经被发现了几十年，最近被证明可以调节动物的寿命。然而，MsrA仅对甲硫氨酸-S-亚砜具有特异性。私家侦探鉴定并表征了对甲硫氨酸-R-亚砜具有特异性的第二种哺乳动物Met（O）还原酶（SelR 1）。SelR 1是一种含硒代半胱氨酸的Jng蛋白，硒影响其表达。这提出了一种可能性，即SelR 1也可能通过降低Met（O）水平参与延缓衰老过程，并且补充硒饮食可能提供延长某些人群寿命的方法。为了直接表征SelR 1在衰老中的作用，将分析哺乳动物中Met（O）减少的途径，重点是SelenoproteinSelR 1的功能和SelR 1缺乏或富集的动物寿命的表征。生物化学和细胞生物学方法以及小鼠模型系统的组合将用于解决以下特定问题（特定目标）：1）SelR 1及其同源物的性质和反应机制是什么？在哺乳动物中已鉴定出三种SelR同工酶。这些蛋白质的野生型和突变形式将被表征，并确定其催化活性、底物特异性、金属结合特性和补充酵母菌株的能力; 2）Met（O）还原酶的组织表达模式、细胞位置和表达调控是什么？假设将被测试，SelR同工酶位于不同的细胞隔室，一个单一的MsrA基因产生两种形式的酶。此外，硒代半胱氨酸插入和调节SelR 1表达的效率将被确定; 3）SelR在衰老中的作用是什么？将产生SelR 1基因敲除小鼠，并测试这些动物的特征在于寿命缩短的假设。还将产生过表达SelR 1的转基因小鼠，以确定这些动物是否具有增加的寿命。

DESCRIPTION (provided by applicant): Methionine sulfoxide (Met(O)) reduction is an essential metabolic pathway that provides protection against oxidative stress and regulates protein function. Met(O) are formed in the presence of reactive oxygen species and are reduced back to methionine by peptide Met(O) reductases. One Met(O) reductase (MsrA) has been known for decades and has recently been shown to regulate lifespan in animals. MsrA, however, is only specific for methionine-S-sulfoxides. The P.I. identified and characterized a second mammalian Met(O) reductase (SelR1) that is specific for methionine-R-sulfoxides. SelR1 is a selenocysteine-contain Jng protein and dietary selenium affects its expression. This raises a possibility that SelR1 may also be involved in delaying the aging process through reduction in levels of Met(O) and that supplementation of diet with selenium may provide means of extending the lifespan of certain segments of the human population. To directly characterize the role of SelR1 in aging, the pathway of Met(O) reduction in mammals will be analyzed with an emphasis on the function of selenoproteinSelR1 and characterization of the lifespan of animals that are either deficient or enriched in SelR1. A combination of biochemical and cell biology approaches and mouse model systems will be used to address the following specific questions (specific aims): 1) What are the properties and reaction mechanisms of SelR1 and its homologs? Three SelR isozymes have been identified in mammals. Wild-type and mutant forms of these proteins will be characterized and their catalytic activities, substrate specificity, metal-binding properties and the ability to complement yeast strains determined; 2) What are the tissue expression patterns, cellular locations and regulation of expression of Met(O) reductases? Hypotheses will be tested that SelR isozymes are located in different cellular compartments and that a single MsrA gene gives rise to two forms of the enzyme. In addition, efficiency of selenocysteine insertion and regulation of SelR1 expression by dietary selenium will be determined; 3) What is the role of SelR in aging? SelR1 knockout mice will generated and the hypothesis tested that these animals are characterized by a reduced lifespan. Transgenic mice overexpressing SelR1 will also be generated to determine whether these animals have increased lifespan.