PH CONTROL OF PROTEIN SYNTHESIS

蛋白质合成的 pH 控制

基本信息

批准号：
6517551
负责人：
Peter James Garlick
金额：
$ 28.98万
依托单位：
STATE UNIVERSITY NEW YORK STONY BROOK
依托单位国家：
美国
项目类别：
财政年份：
2000
资助国家：
美国
起止时间：
2000-06-01 至 2004-05-31
项目状态：
已结题

项目摘要

Patients with renal failure, diabetic ketosis, severe trauma or sepsis often become acidotic. Moreover, they are also susceptible to body protein wasting. Experimental acidosis has been shown to result in negative nitrogen balance, and body protein loss in acidotic patients can be alleviated by normalization of pH. Previous work has concentrated on the effects of pH on protein degradation and no systematic studies have been performed on pH and protein synthesis. However, measurements in animals and human volunteers have shown that both metabolic and respiratory acidosis are associated with depressed rates of synthesis of skeletal muscle protein and serum albumin. The purpose of the present proposal is therefore to characterize the relationship between protein synthesis rates in tissues, especially muscle and liver, of rats and humans in relation to changes in intra- and extracellular pH, to confirm the hypotheses: (i) that changes in blood pH, both by metabolic and respiratory means, modify rates of tissue protein synthesis and gene expression and contribute to the protein wasting of patients with acidosis, and (ii) that these effects of pH operate directly via the intracellular pH and do not involve extracellular mediators such as hormones. The studies will employ measurements of rates of protein synthesis in tissues of rats and human volunteers to characterize the responses to changes in intra- and extracellular pH induced by metabolic and respiratory means and to confirm that these effects are rapid, operate over the full range of pH from acidosis to alkalosis and are independent of oxygen supply. In the animals, the responses of gene expression in the liver will be investigated by determining the levels of mRNA for 3 liver proteins. In particular, the treatments studied will produce different changes in the infra- and extracellular pH. Measurements of intracellular pH will be made by nuclear magnetic resonance, to confirm the hypothesis that changes in protein synthesis are determined by the intracellular rather than extracellular pH. A separate set of studies will be performed in isolated tissues and cells, to determine whether responses to changes in pH are direct or act through circulating hormones. The cellular and molecular mechanisms through peptide chain initiation and initiation factors eIF-2 and eIF-4 will also be identified. Finally, the effect of changes in pH on tissue protein synthesis will be measured in human volunteers and hemodialysis patients, to identify the role of pH control of protein synthesis in health and in protein wasting conditions with abnormalities of pH control.

患有肾功能衰竭、糖尿病酮症、严重创伤或败血症的患者常常会出现酸中毒。此外，它们还容易受到体内蛋白质浪费的影响。实验性酸中毒已被证明会导致负氮平衡，酸中毒患者的体内蛋白质损失可以通过 pH 值正常化来缓解。以往的工作主要集中在pH值对蛋白质降解的影响上，尚未对pH值和蛋白质合成进行系统的研究。然而，对动物和人类志愿者的测量表明，代谢性酸中毒和呼吸性酸中毒都与骨骼肌蛋白和血清白蛋白合成率降低有关。因此，本提案的目的是描述大鼠和人类组织（尤其是肌肉和肝脏）中蛋白质合成速率与细胞内和细胞外 pH 值变化之间的关系，以证实以下假设：（i）血液 pH 值通过代谢和呼吸方式改变组织蛋白合成和基因表达的速率，并导致酸中毒患者的蛋白质浪费，并且 (ii) pH 值的这些影响直接通过细胞内 pH 值起作用，不涉及细胞外中介者如荷尔蒙。这些研究将采用测量大鼠和人类志愿者组织中蛋白质合成速率的方法来表征对代谢和呼吸方式引起的细胞内和细胞外pH变化的反应，并确认这些影响是快速的，在整个范围内发挥作用。 pH值从酸中毒到碱中毒并且与氧气供应无关。在动物中，将通过测定 3 种肝脏蛋白的 mRNA 水平来研究肝脏中基因表达的反应。特别是，所研究的治疗方法会导致细胞内和细胞外 pH 值发生不同的变化。将通过核磁共振测量细胞内 pH 值，以证实蛋白质合成的变化是由细胞内而不是细胞外 pH 值决定的假设。一组单独的研究将在分离的组织和细胞中进行，以确定对 pH 值变化的反应是直接的还是通过循环激素起作用。还将确定通过肽链起始和起始因子 eIF-2 和 eIF-4 的细胞和分子机制。最后，将在人类志愿者和血液透析患者中测量pH变化对组织蛋白质合成的影响，以确定蛋白质合成的pH控制在健康和pH控制异常的蛋白质消耗条件下的作用。