PRENYLATION, MEMBRANE ASSOCIATION, AND RAS TRANSFORMATIO

尽管我们对ras蛋白结构和 生物化学，我们仍然对两者的确切生物功能一无所知 正常ras蛋白在正常细胞生长中的作用及其机制 致癌的ras蛋白可触发恶性细胞的异常生长。这个 最近观察到ras蛋白的翻译后修饰 通过法尼基异戊二烯(胆固醇的一种重要中间体) 生物合成)是ras膜结合和转化的关键。 活动为RAS研究提出了两个新方向：1)具体地说 阻断ras蛋白的法尼基修饰作为一种新的方法 合理的癌症治疗药物设计；2)确定合理的治疗方案 这种脂质修饰对正常和致癌RAS的意义 生物活动。 这项建议中的实验研究是基于最近的 观察到法尼基异戊二烯取代正常 香叶基香叶基异戊二烯的RAS反应产生了一类新的显性 抑制性ras突变蛋白，而脂肪酸的替代 肉豆蔻酸盐产生了一种转化蛋白。这两种脂类都可以 促进致癌ras的膜结合和生物学功能 蛋白质。因此，尽管膜结合对ras至关重要。 功能，正常和致癌的ras蛋白明显具有不同的功能 这一协会的要求可能反映了他们对 明显不同的有丝分裂信号转导途径。具体的 这项建议的目的是确定(1)蛋白质预烯基化的作用 在正常和致癌ras蛋白的生物学活性中，(2) 质膜结合在RAS生物活性中的作用 这一作用对于正常和致癌蛋白是不同的，(3)确定 特定类型的脂类对蛋白质进行特定修饰的基础 (异戊二烯与脂肪酸)，以及(4)是否特定的 脂类修饰的性质和潜在的亚细胞定位 新的癌基因蛋白TC21与ras共享。这些目标将是 通过比较真正的生物化学和生物学来探讨 异源修饰的法尼化ras突变形式的ras 脂类。这些研究应该大大有助于理解 正常和致癌ras蛋白的生化功能并提供 了解不同组织的贡献的重要基础 对其他蛋白质功能的脂质修饰，包括src， 异三聚体G蛋白和ras相关蛋白，调节不同的 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.