PRENYLATION, MEMBRANE ASSOCIATION, AND RAS TRANSFORMATIO

尽管我们对ras蛋白质结构有相当的了解， 在生物化学方面，我们仍然不知道 正常细胞生长中的正常ras蛋白质的研究以及 致癌Ras蛋白触发恶性细胞的异常生长。的 最近观察到ras蛋白的翻译后修饰 法呢基类异戊二烯（胆固醇的重要中间体 生物合成）对于ras膜结合和转化至关重要 活动促使RAS研究有两个新方向：1）具体 阻断ras蛋白的法尼基修饰作为一种新的方法， 癌症治疗的合理药物设计，以及2）确定 这种脂质修饰对正常和致癌ras意义 生物活动。 本提案中的实验研究基于最近的 观察到法呢基类异戊二烯在正常 ras通过香叶基香叶基类异戊二烯产生了一类新的优势 抑制ras突变蛋白，而脂肪酸的取代 肉豆蔻酸酯产生转化蛋白。 这些脂质中的任何一种都可以 促进癌基因ras的膜结合和生物学功能 proteins.因此，尽管膜结合对于ras至关重要， 功能，正常和致癌ras蛋白显然具有不同的 对该协会的要求，可能反映他们的监管， 不同的促有丝分裂信号转导途径。具体 该建议的目的是确定（1）蛋白质异戊二烯化的作用 在正常和致癌ras蛋白的生物活性中，（2） 质膜结合在ras生物学活性中的作用， 这一作用对于正常蛋白和致癌蛋白是不同的，（3）为了确定 特定类型脂质对蛋白质进行特定修饰的基础 （类异戊二烯与脂肪酸），以及（4）特定的 脂质修饰的性质和电位的亚细胞定位 新的癌基因蛋白TC 21与ras共有。 这些目标将是 通过比较真实的生物化学和生物学来探讨 法尼基化的ras转化为经异源性修饰的ras的突变形式， 脂质。 这些研究应该有助于理解 正常和致癌ras蛋白生化功能，并提供 这是理解不同国家的贡献的重要基础， 脂质修饰对其他蛋白质的功能，包括src， 异源三聚体G蛋白和ras相关蛋白，调节多种 正常的细胞过程。

Despite our considerable knowledge of ras protein structure and biochemistry, we remain ignorant both of the precise biological function of normal ras proteins in normal cell growth and of the mechanism whereby oncogenic ras proteins trigger the aberrant growth of malignant cells. The recent observation that the posttranslational modification of ras proteins by a farnesyl isoprenoid (an essential intermediate in cholesterol biosynthesis) is critical for ras membrane association and transforming activity has prompted two new directions for ras studies: 1) specifically blocking the farnesyl modification of ras proteins as a novel method of rational drug design for cancer treatment, and 2) determining the significance of this lipid modification for normal and oncogenic ras biological activities. The experimental studies in this proposal are based on the recent observations that the substitution of the farnesyl isoprenoid on normal ras by a geranylgeranyl isoprenoid gave rise to a new class of dominant inhibitory ras mutant protein, whereas the substitution of the fatty acid myristate gave rise to a transforming protein. Either of these lipids can promote the membrane association and biological function of oncogenic ras proteins. Therefore, although membrane association is critical for ras function, normal and oncogenic ras proteins apparently possess different requirements for this association that may reflect their regulation of distinctly different mitogenic signal transduction pathways. The specific aims of this proposal are to determine (1) the role of protein prenylation in the biological activity of normal and oncogenic ras proteins, (2) the role of plasma membrane association in ras biological activity and whether this role differs for normal and oncogenic proteins, (3) to determine the basis for specific modification of proteins by specific types of lipids (isoprenoids versus fatty acids), and (4) whether the particular properties of lipid modification and subcellular location of a potential new oncogene protein, TC21, are shared with ras. These aims will be approached by comparing the biochemistry and biology of authentically farnesylated ras to mutant forms of ras that modified by heterologous lipids. These studies should contribute significantly to understanding the biochemical function of normal and oncogenic ras proteins and provide an important foundation for understanding the contribution of different lipid modifications to the function of other proteins, including src, the heterotrimeric G proteins, and ras-related proteins, that regulate diverse normal cellular processes.