REGULATION OF THE SECRETION OF APOB-LIPOPROTEINS

血浆胆固醇、LDL胆固醇和LDL浓度升高 载脂蛋白B被认为是发生 动脉粥样硬化 血浆中的LDL水平将显著降低 受LDL受体活性调节，尤其是肝LDL受体 活动 然而，LDL浓度也受到以下因素的影响： VLDL分泌和转化为LDL。 在过去的几年里， 很明显，含有载脂蛋白B的颗粒的过度产生，而不 伴随着相当的增加，在他们的分数分解率，是 高胆固醇血症患者的高胆固醇血症。 因此，拟开展的研究将探讨载脂蛋白B的调控 在人肝癌细胞（Hep G2）中的分泌，以及后来在 原代人肝细胞。 我的实验室最近完成的一项研究表明， 由Hep G2细胞合成的apo B分子中有10%是分泌的，事实上， 很大一部分在合成后很快被迅速降解。 此外，本发明还提供了一种方法， 在培养基中添加油酸， 新生载脂蛋白B细胞内降解。 因此，似乎A 翻译后机制负责决定 由肝细胞分泌的apo B分子。 这是PI的整体 含有载脂蛋白B的脂蛋白的分泌受到调节的假说 通过将载脂蛋白B导向降解或分泌的过程 途径。 这将是重要的，在理解的规则， 载脂蛋白B分泌，以更详细地定义这一途径，并研究 因素影响它。 因此，这项建议的具体目标是：1）划定员额， 翻译机制，调节新合成的 由Hep G2细胞分泌的apo B。 2)确定油酸如何改变 上述降解机制，并保护新生载脂蛋白B 细胞内降解 3)确定细胞内的变化 胆固醇利用率影响载脂蛋白B的降解机制。 四、 确定apo B分子的哪些结构域参与了 转染Hep G2对apo B细胞内降解的调节 具有编码截短的载脂蛋白B分子的cDNA的细胞。

Increased concentrations of plasma cholesterol, LDL cholesterol, and LDL apo B have been implicated as risk factors for the development of atherosclerosis. The levels of LDL in plasma will be significantly regulated by LDL receptor activity, especially hepatic LDL receptor activity. However, LDL concentrations are also influenced by the rates of VLDL secretion and conversion to LDL. In the last several years it has become evident, that overproduction of apo B-containing particles, without an accompanying comparable increase in their fractional catabolic rate, is responsible for a large percentage of patients with hypercholesterolemia. Therefore, the proposed studies will investigate the regulation of apo B secretion in human hepatoma cells (Hep G2) and, later, in cultures of primary human hepatocytes. A study recently completed in my laboratory has shown that only a fraction of the apo B molecules synthesized by Hep G2 cells are secreted, in fact, a large proportion are rapidly degraded soon after synthesis. In addition, adding oleic acid to the culture medium had the effect of protecting nascent apo B from intracellular degradation. Thus, it appears that a post-translational mechanism is responsible for determining the number of apo B molecules secreted by the hepatocyte. It is the PI's overall hypothesis that the secretion of apo B-containing lipoproteins is regulated by processes which direct apo B to either the degradative or secretory pathways. It will be important in the understanding of the regulation of apo B secretion to define this pathway in more detail and study what factors affect it. Therefore, the specific aims of this proposal are: 1) Delineate the post- translational mechanism which regulates the proportion of newly synthesized apo B that is secreted by Hep G2 cells. 2) Determine how oleic acid alters the above degradative mechanism and protects nascent apo B from intracellular degradation. 3) Determine whether changes in cellular cholesterol availability affect the apo B degradative mechanism. 4) Determine which domains of the apo B molecule are involved in the regulation of intracellular degradation of apo B by transfecting Hep G2 cells with cDNAs coding for truncated apo B molecules.