Contribution of m-tyrosine to the adverse effects of oxidative stress

 描述(申请人提供)：氧化应激随着年龄的增长而增加，可能导致各种与年龄相关的疾病，但氧化应激导致细胞损伤并导致衰老的过程及其相关的病理机制尚不完全清楚。这项建议旨在研究非典型酪氨酸异构体在氧化应激的有害影响中的作用。非典型酪氨酸异构体与内源性酪氨酸不同，其羟基位于苯环上。在氧化应激条件下，羟基自由基能攻击苯丙氨酸的苯基环，形成包括偏酪氨酸在内的这些异常的酪氨酸异构体。几十年来，m-酪氨酸浓度的升高一直被简单地作为氧化应激负担的替代标志来测量。然而，新出现的证据表明，m-酪氨酸直接对细胞有害，实际上可能有助于氧化应激诱导的细胞损伤和疾病发病机制。M-酪氨酸有害作用的一种机制是这种氨基酸异常地充电到苯丙氨酸-tRNA上，然后导致m-酪氨酸进入新合成的蛋白质中。考虑到疏水性苯丙氨酸和极性m-酪氨酸残基之间的化学差异，这可能会对这些蛋白质产生一系列影响，但这些取代引发的最终下游后果仍未被探索。这项拟议的项目旨在利用模式生物线虫来阐明m-酪氨酸对细胞有毒的下游途径，可能是通过诱导细胞凋亡途径，并探索酪氨酸转氨酶在细胞抗氧化反应中的新作用，该酶通过代谢m-酪氨酸，从而阻止整合到蛋白质中。我们设计了三个目标来评估这一假说。由于线虫种系在暴露于m-酪氨酸后发生显著变化，因此Aim 1将确定m-酪氨酸是否通过诱导细胞凋亡对线虫种系产生不利影响。目的研究酪氨酸氨基转移酶能否在体内和体外催化m-酪氨酸代谢，从而降低其毒性作用。AIM 3将使用最近在 研究m-酪氨酸毒性所必需的细胞通路的正向遗传学筛查。该项目的成功完成将扩大目前对氧化应激产生的m-酪氨酸如何促进细胞毒性和疾病病理学的理解。此外，这些研究将通过消除有毒的酪氨酸异构体来确定酪氨酸转氨酶在细胞抗氧化反应中的新作用。该项目的结果可能反过来导致年龄相关疾病的新疗法的开发，在这些疾病中，m-酪氨酸起着直接的病理作用。除了研究项目，该提案还包括一个培训部分，涉及课程作业、会议和职业发展活动，以促进学员发展成为一名能够在研究和病人护理方面发挥领导作用的内科科学家。

 DESCRIPTION (provided by applicant): Oxidative stress increases with age and likely contributes to a variety of age-related diseases, but the processes by which oxidative stress causes cellular damage and contributes to aging and its associated pathologies are not completely understood. This proposal seeks to study the role of atypical tyrosine isomers, which differ from endogenous tyrosine in the positioning of their hydroxyl group on the benzyl ring, in the harmful effects of oxidative stress. Under conditions of oxidative stress, hydroxyl radicals can attack the benzyl ring of phenylalanine and form these abnormal tyrosine isomers including meta-tyrosine. For decades elevations in m-tyrosine concentrations have been measured simply as a surrogate marker of oxidative stress burden. However, emerging evidence suggests m-tyrosine is directly harmful to cells and may actually contribute to oxidative stress-induced cell damage and disease pathogenesis. A proposed mechanism for the harmful effects of m-tyrosine is the aberrant charging of this amino acid to phenylalanine-tRNA which then results in the subsequent incorporation of m-tyrosine into newly synthesized proteins. Potentially this could have a range of effects on these proteins given the chemical differences between the hydrophobic phenylalanine and the polar m-tyrosine residue, but the ultimate downstream consequences triggered by these substitutions remain unexplored. The proposed project seeks to utilize the model organism C. elegans to elucidate the downstream pathways by which m-tyrosine is toxic to cells, perhaps via the induction of apoptotic pathways, and to also explore a novel role for the enzyme tyrosine aminotransferase within the cellular antioxidant response by metabolizing m-tyrosine and hence preventing incorporation into proteins. Three aims have been designed to assess this hypothesis. Because the C. elegans germline is significantly altered following exposure to m-tyrosine, Aim 1 will determine whether m-tyrosine adversely affects the C. elegans germline by inducing apoptosis. Aim 2 will determine whether tyrosine aminotransferase can catalyze the metabolism of m-tyrosine and thus reduce its toxic effects both in vitro and in vivo. Aim 3 will use novel resistance mutants that were recently identified in a forward genetic screen to study cellular pathways essential for m-tyrosine toxicity. The successful completion of this project will extend the current understanding of how m-tyrosine generated by oxidative stress contributes to cell toxicity and disease pathology. Furthermore, these studies would define a novel role for tyrosine aminotransferase within the cellular antioxidant response through the elimination of toxic tyrosine isomers. The results from this project may in turn lead to the development of new therapies for age-associated diseases in which m-tyrosine plays a direct pathologic role. In addition to the research project, the proposal also includes a training component involving coursework, conferences, and career development activities to promote the trainee's development into a physician-scientist who will be able to have a leadership role in research and patient care.