PHOSPHATIDYLETHANOLAMINE AND CELL PROLIFERATION

我们研究的长期目标是了解 细胞增殖和分化的调控机制 正常和肿瘤性乳腺上皮细胞。哺乳动物细胞 可归类为乙醇胺(ETN)反应或- 对他们的成长反应迟钝。正常乳腺细胞 是ETN反应的，一些肿瘤乳腺细胞也是ETN- 反应性，而其他肿瘤乳腺细胞是ETN- 没有反应。在ETN反应细胞中从头合成 磷脂酰乙醇胺(PE)由于减少了 丝氨酸交换酶的活性，该酶负责 PE前体磷脂酰丝氨酸(PS)的生物合成。什么时候 培养液中不添加膜磷脂ETN 在ETN反应的细胞中，PE缺乏，增殖 停下来。眼下的目标是阐明生物化学 乳腺细胞对ETN的反应和无反应的机制 并确定负责授权给 细胞ETN-无反应。目前的提案有三个 明确的目标。 第一个目的是阐明活性降低的原因 ETN反应细胞中的丝氨酸交换酶。被缩减的 这种酶的活性似乎不是由有限的 酶的数量，而不是由于实际的减少 活动。这种酶的性质将用 粗细胞提取液和微粒体组分。 第二个目的是分析体育缺乏对健康的影响。 细胞外信号转导，以阐明 PE缺乏导致细胞增殖停止的机制。 我们已经有明确的迹象表明一种信号转导 促进肿瘤的佛波酯和EGF受体不起调节作用 正确地进行。结合特性的进一步分析 将进行EGF和胰岛素治疗。 第三个目标是识别和分离出 使单元格ETN无响应。这一目标将会实现 通过1)研究INT-1和INT-2癌基因，这些癌基因最初是 显示将ETN响应性细胞转换为-无响应性，以及2) 从对ETN无反应的人乳房中分离DNA片段 ETN反应性大鼠肿瘤细胞株的建立 细胞。 这些研究将有助于理解 细胞膜磷脂在多种细胞代谢过程中的作用 恶性肿瘤的进展过程。

The long term objective of our research is to understand the regulatory mechanisms of proliferation and differentiation of normal and neoplastic mammary epithelial cells. Mammalian cells in culture can be classified as ethanolamine (Etn)-responsive or - nonresponsive with regard to their growth. Normal mammary cells are Etn-responsive and some neoplastic mammary cells are also Etn- responsive, whereas other neoplastic mammary cells are Etn- nonresponsive. In Etn-responsive cells de novo biosynthesis of phosphatidylethanolamine (PE) is limited due to the reduced activity of the serine exchange enzyme which is responsible for the biosynthesis of the precursor of PE, phosphatidylserine (PS). When the medium is not supplemented with Etn, the membrane phospholipid in Etn-responsive cells becomes PE-deficient, the proliferation stops. The immediate objective is to elucidate the biochemical mechanism of Etn-responsive and -nonresponsiveness of mammary cells and to identify the gene or genes responsible for conferring to the cells Etn-nonresponsiveness. The present proposal has three specific aims. The first aim is to elucidate the cause of the reduced activity of the serine exchange enzyme in Etn-responsive cells. The reduced activity of the enzyme does not seem to result from a limited amount of enzyme, but rather results from an actual reduction in activity. The properties of the enzyme will be examined using crude cell extract and the microsomal fraction. The second aim is to analyze the effect of PE-deficiency on extracellular signal transductions in order to elucidate the mechanism of cessation of cell proliferation due to PE-deficiency. We already have clear indications that a signal transduction mediate by tumor promoting phorbol esters and EGF receptor does not proceed properly. Further analyses of binding characteristics of EGF and insulin will be carried out. The third aim is to identify and isolate the gene (or genes) which renders the cell Etn-nonresponsive. This aim will be accomplished by 1) studying int-1 and int-2 oncogenes which have initially been shown to convert Etn-responsive cells to -nonresponsive, and 2) isolating DNA fragment from an Etn-nonresponsive human breast carcinoma cell line by transfection of Etn-responsive rat carcinoma cells. These studies will contribute to the understanding of the role of membrane phospholipids in various cellular metabolic processes and the process of malignant tumor progression.