Mechanism of Selenoprotein Synthesis

说明(申请人提供)：硒是一种必需的微量元素，长期以来一直以其抗氧化特性而闻名，其中大部分或全部可归因于硒蛋白。硒蛋白在生命的各个方面发挥作用，从早期发育到与衰老相关的疾病，以及介于两者之间的大多数生物过程。我们对硒是如何结合到硒蛋白中的理解已经取得了相当大的进展，但我们的知识中仍然存在着主要的空白，包括当微量元素有限时，如何在关键组织中优先保留和利用硒。同样，当缺硒时，一些硒蛋白优先于其他硒蛋白合成的机制仍然是个谜。硒半胱氨酸通过硒半胱氨酸裂解酶在体内循环，我们对该酶在硒供应中的作用知之甚少。这项建议的总体目标是阐明硒半胱氨酸裂解酶在硒蛋白合成中的作用，并研究硒半胱氨酸裂解酶在硒蛋白P基因敲除导致硒转运受损时的作用。我们研究的长期目标是了解调控硒分布和硒蛋白合成的调控途径背后的潜在分子、细胞和组织特异性机制。这些目标的实现将提供对我们进一步了解如何利用硒实现最佳健康至关重要的信息。我们的中心假设是，硒半胱氨酸裂解酶在组织和硒蛋白特异性的硒半胱氨酸循环中发挥作用，有助于在微量元素有限的情况下，最关键的组织和硒蛋白优先摄取硒。我们的中心假设将通过以下具体目标得到验证：1)表征硒半胱氨酸裂解酶基因敲除对组织硒蛋白mRNA和蛋白质表达的影响，以及对解剖学、生理学、组织病理学、神经运动功能和神经行为的影响；2)建立硒半胱氨酸裂解酶-硒蛋白P基因敲除小鼠，并按照目标1的描述进行特征描述；以及3)表征与硒蛋白mRNAs相关的mRNP，这些mRNP在目标1和2的条件下被保存或定向降解。这些研究将为硒蛋白mRNAs的分布、硒蛋白合成和避免无意义介导的衰变提供新的见解。

DESCRIPTION (provided by applicant): Selenium is an essential trace element long known for its antioxidant properties, most or all of which are attributable to selenoproteins. Selenoproteins function in all aspects of life, from early development through diseases associated with aging, and most of the biological processes in between. Considerable progress has been made in our understanding of how selenium is incorporated into selenoproteins, but major gaps in our knowledge remain, including how selenium is preferentially retained and utilized in crucial tissues when the trace element is limiting. Likewise, the mechanisms dictating preferential synthesis of some selenoproteins over others when selenium is deficient remain enigmatic. Selenocysteine is recycled in the body via selenocysteine lyase, and our knowledge about the role of this enzyme in selenium supply is minimal. The overall objectives of this proposal are to elucidate the role of selenocysteine lyase in contributing to the hierarchy of selenoprotein synthesis, and to investigate the contributions of selenocysteine lyase when selenium transport is impaired due to selenoprotein P knockout. The long-term goals of our research are to understand the underlying molecular, cellular and tissue-specific mechanisms behind the regulatory pathways governing selenium distribution and selenoprotein synthesis. Achievement of these goals will provide information that is essential to furthering our understanding of how selenium is utilized for optimum health. Our central hypothesis is that selenocysteine lyase functions in tissue- and selenoprotein-specific recycling of selenocysteine, contributing to mechanisms whereby the most crucial tissues and selenoproteins have priority on selenium when the trace element is limiting. Our central hypothesis will be tested via the following specific aims: 1) characterize the effects of selenocysteine lyase knockout on tissue selenoprotein mRNA and protein expression, and effects on anatomy, physiology, histopathology, neuromotor function and neurobehavior; 2) generate combined selenocysteine lyase- selenoprotein P knockout mice, and characterize as described for aim 1; and 3) characterize mRNPs associated with selenoprotein mRNAs that are either preserved or targeted for degradation under the conditions in aims 1 and 2. These studies will provide new insights into the mechanisms of selenium distribution, selenoprotein synthesis, and circumventing nonsense-mediated decay of selenoprotein mRNAs.