Methionine sulfoxide reduction, selenium and aging

描述(由申请人提供)：蛋氨酸亚砜(Met(O))还原是一种重要的代谢途径，提供对氧化应激的保护和调节蛋白质功能。Met(O)在活性氧存在的情况下形成，并通过多肽Met(O)还原酶还原为蛋氨酸。一种甲硫氨酸(O)还原酶(MSRA)已经知道几十年了，最近被证明可以调节动物的寿命。然而，MSRA仅对蛋氨酸-S-亚硫醚具有特异性。P.I.鉴定并鉴定了第二个哺乳动物Met(O)还原酶(SelR1)，该酶是蛋氨酸-R-亚硫醚的专有基因。SelR1是一种含硒半胱氨酸的JNG蛋白，膳食硒影响其表达。这提出了一种可能性，SelR1可能还参与了通过降低Met(O)水平来延缓衰老过程，补充硒的饮食可能提供了延长某些人类群体寿命的手段。为了直接描述SelR1在衰老中的作用，将分析哺乳动物中Met(O)还原的途径，重点是SelR1的功能以及SelR1缺乏或丰富的动物的寿命特征。将结合生物化学和细胞生物学的方法和小鼠模型系统来解决以下具体问题(具体目的)：1)SelR1及其同系物的性质和反应机制是什么？已在哺乳动物中鉴定出三种SelR同工酶。将对这些蛋白质的野生型和突变型进行鉴定，并确定它们的催化活性、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？假设SelR同工酶位于不同的细胞隔间，并且一个MSRA基因产生两种形式的酶，这一假设将得到检验。此外，将确定硒半胱氨酸的插入效率和膳食硒对SelR1表达的调节；3)SelR在衰老中的作用是什么？将产生SelR1基因敲除小鼠，并检验假设，即这些动物的特征是寿命缩短。还将产生过度表达SelR1的转基因小鼠，以确定这些动物是否延长了寿命。

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.