PEROXISOMAL HMG-COA REDUCTASE

在过去的几年里，这个组织和其他人已经证明了 大鼠肝脏过氧化物酶体参与胆固醇合成。 过氧化物酶体含有以下酶和蛋白质， 胆固醇合成：1）3-羟基-3-甲基戊二酰辅酶A（HMG-CoA） 还原酶，胆固醇合成的限速酶; 2） 胆固醇合成初始步骤所必需的硫解酶活性; 和3）细胞固醇载体蛋白2（SCP-2），一种 胆固醇利用和生物合成的几个步骤。 此外，本发明还提供了一种方法， 过氧化物酶体可以在存在下将甲羟戊酸转化为胆固醇， 胞质蛋白质 这些意想不到的发现提出了有趣的问题 过氧化物酶体中蛋白质的特性 胆固醇合成，过氧化物酶体合成胆固醇的命运，以及 过氧化物酶体系统的调节和功能。 这项建议会 重点关注以下方面： 1.过氧化物酶体HMG-CoA还原酶的纯化和生产 过氧化物酶体特异性的多克隆和单克隆抗体 还原酶; 2.大鼠和/或小鼠过氧化物酶体HMG-CoA的cDNA克隆 还原酶及其核苷酸序列的测定; 3.人过氧化物酶体HMG-CoA还原酶cDNA的克隆。 我们已经表明 过氧化物酶体HMG-CoA还原酶构成了大多数 人肝癌细胞系HepG 2中的免疫活性物质; 4.过氧化物酶体HMG-CoA还原酶的调节分析。 由于过氧化物酶体是生命所必需的， 参与胆固醇代谢，这是至关重要的，以获得答案， 以下问题。 过氧化物酶体HMG-CoA的结构是什么 还原酶是如何调节的？的意义是什么 胆固醇合成系统中的过氧化物酶体？这是一条什么样的道路呢？ 过氧化物酶体胆固醇合成胆固醇的命运是什么 由过氧化物酶体合成：用于胆汁酸合成，类固醇 激素合成维生素D还是脂蛋白过氧化物酶体胆固醇 合成发生在肝脏以外的组织中？只有系统地研究 过氧化物酶体中参与胆固醇合成的蛋白质将开始 回答以上问题。 了解其功能至关重要， 过氧化物酶体还原酶和胆固醇合成的命运 过氧化物酶体之前，我们可以开始评估的意义和作用， 过氧化物酶体胆固醇合成调节总胆固醇 体内平衡

In the last few years, it has been demonstrated by this group and others that rat liver peroxisomes participate in cholesterol synthesis. Peroxisomes contain the following enzymes and proteins involved in cholesterol synthesis: 1) 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme of cholesterol synthesis; 2) the thiolase activity necessary for the initial step in cholesterol synthesis; and 3) cellular sterol carrier protein 2 (SCP-2), a protein required for several steps in cholesterol utilization and biosynthesis. In addition, peroxisomes can convert mevalonic acid to cholesterol in the presence of cytosolic proteins. These unexpected findings raise interesting questions about the characteristics of the proteins involved in peroxisomal cholesterol synthesis, the fate of peroxisome-synthesized cholesterol, and the regulation and function of the peroxisomal system. This proposal will focus on the following: 1. Purification of peroxisomal HMG-CoA reductase and production of polyclonal and monoclonal antibodies that are specific for the peroxisomal reductase; 2. Cloning of the cDNA for the rat and/or mouse peroxisomal HMG-CoA reductase and determination of its nucleotide sequence; 3. Cloning of the human peroxisomal HMG-CoA reductase cDNA. We have shown that the peroxisomal HMG-CoA reductase constitutes the majority of the immunoreactive material in the human hepatoma cell line HepG2; 4. Analysis of the regulation of the peroxisomal HMG-CoA reductase. Since peroxisomes are essential for life, and have also been shown to be involved in cholesterol metabolism, it is critical to obtain answers to the following questions. What is the structure of the peroxisomal HMG-CoA reductase and how is it regulated? What is the significance of the cholesterol synthesis system in peroxisomes? What is the pathway of peroxisomal cholesterol synthesis? What is the fate of the cholesterol synthesized by peroxisomes: is it used for bile acid synthesis, steroid hormone synthesis, vitamin D, or lipoproteins? Does peroxisomal cholesterol synthesis occur in tissues other than the liver? Only a systematic study of the proteins involved in cholesterol synthesis in peroxisomes will begin to answer the above questions. It is essential to understand the function of the peroxisomal reductase and the fate of the cholesterol synthesized by peroxisomes before we can begin to assess the significance and the role of peroxisomal cholesterol synthesis in regulation of total cholesterol homeostasis.