NUTRITIONAL REGULATION OF RAS PROTO-ONCOGENE ACTIVITY

该项目的目标是调查营养与健康之间的联系。 因子和ras蛋白的活性。 虽然这种原癌基因产物的细胞功能仍然存在， RAS从正常调节中逃逸可能导致 形态转变，似乎是一个频繁的事件， 癌症的多步骤发生。 营养状况可能影响ras活性 通过影响蛋白质的翻译后脂质修饰 这是质膜定位和活性所必需的。 可以想象，这种脂质效应可能与流行病学有关。 饮食脂肪与结肠癌和乳腺癌之间的相关性。 探讨营养素和营养素对ras活性的影响， 通过相对蛋白质水平和细胞定位评估， 开发了一种灵敏的半定量免疫测定法。 等 敏感性消除了对突变表达的细胞系的需要， 激活的或基因扩增水平的ras蛋白，其中 RAS可能被不适当地调节或可能表现出异常活性。 能够使用表达正常低水平和 难以检测的蛋白质水平可能对阐明 营养因素影响ras。 我们用这个系统来调查 似乎具有抗癌活性的化合物的作用。 我们有 发现类固醇脱氢表雄酮（DHEA）降低 ras蛋白在多种细胞系中的表达。 DHEA是一种有效的非竞争性 葡萄糖-6-磷酸脱氢酶抑制剂， 中间代谢，但也可以通过调节细胞活性， 对内源性甲羟戊酸库的影响。 该系统将使我们能够 研究这种和其他潜在的RAS调节剂的作用 活动

The goal of this project is to investigate links between nutritional factors and the activity of ras proteins in a cell culture system. Although the cellular function of this proto-oncogene product remains to be determined, escape by ras from normal regulation can result in morphological transformation and appears to be a frequent event in the multi-step genesis of cancer. Nutritional status may affect ras activity by influencing the post-translational lipid modifications of the protein that are required for plasma membrane localization and hence activity. Conceivably, such lipid effects could be involved in the epidemiologic correlations between dietary fat and colon and breast cancers. To investigate the effects of nutrients and anutrients on ras activity, as assessed by relative protein levels and cellular localization, we have developed a sensitive and semi-quantitative immunoassay. Such sensitivity obviates the need for cell lines expressing mutationally activated or genetically amplified levels of ras protein, cells in which ras may be inappropriately regulated or may exhibit abnormal activities. Being able to use cells that express the normally low and difficult-to-detect levels of protein may be crucial to elucidating how nutritional factors affect ras. We are using this system to investigate the effects of compounds that seem to have anti-cancer activity. We have found that the steroid dehydroepiandrosterone (DHEA) decreases levels of ras protein in a variety of cell lines. DHEA is a potent uncompetitive inhibitor of glucose-6-phosphate dehydrogenase, a key enzyme of intermediate metabolism, but may also modulate cellular activity through effects on endogenous mevalonate pools. This system will enable us to investigate the effects of this and other potential modulators of ras activity.