REGULATION OF MEMBRANE BIOSYNTHESIS BY CSF 1

研究计划的长期目标是了解 膜磷脂的生物发生与生物合成的相互关系 生长因子对造血细胞生理学的调节。 磷脂酰胆碱(PtdCho)是公认的主要结构建筑 生物膜块和二酰基甘油的前体 刺激细胞表面后的二十烷类第二信使 感受器。研究将集中在CTP：磷胆碱 胞苷转移酶(CT)，控制PtdCho速率的酶 生物合成，以及PtdCho代谢与生长的关系 细胞集落刺激中的因子刺激与细胞周期进展 因子1(CSF-1)依赖的小鼠巨噬细胞系。膜 磷脂合成是一个受细胞周期调控的过程，受 PtdCho合成与降解的相互作用。PtdCho降解 受Gi期生长因子刺激和PtdCho合成的调节 是由周期性CT磷酸化控制的。反过来，PtdCho也会影响 细胞周期调节。AN对S相PtdCHO合成的抑制作用 抗肿瘤溶血磷脂酰胆碱类似物导致细胞停滞 BAC1.2F5巨噬细胞处于G2期，随后发生凋亡。这项研究 表明PtdCho的合成是一个必要的过程，受到 这类独特的抗癌药物，从而定义了它们的作用机制 CT作为新的抗癌药物靶点的作用和鉴定。这些数据 也揭示了PtdCho合成和细胞周期之间的相互作用 确保膜形成与细胞协调的机器 成长。所提议的项目的目标是阐明 这些细节构成了这个监管循环的基础。实验计划是 围绕三个具体目标组织，将涉及： 1)主要的磷酸化位点Ser-315上CT磷酸化的作用 在体内，通过细胞周期蛋白依赖性蛋白激酶对PtdCHo的调节 新陈代谢， 2)脑脊液中CT和PtdCho合成失活的机制 被剥夺的细胞，以及 3)细胞膜PtdCho含量和细胞周期的调节 CT在脑脊液-1刺激的PtdCho降解中的作用这些实验是 旨在生成新信息，这些信息将有助于 对进入、运输和转运过程中膜磷脂形成的理解 退出细胞周期。因为只有一个CT基因，而且 蛋白质，这一无处不在的调控因子的拟议研究 磷脂合成与其他哺乳动物细胞直接相关 系统。确定CT和PtdCho在细胞生长和功能中的作用 将提供对开发有用的重要信息 开发CDP-胆碱中CT和其他酶的新方法 作为治疗靶点的途径。

The long term goal of the research plan is to understand the interrelationship between the biogenesis of membrane phospholipids and growth factor regulation of hematopoietic cell physiology. Phosphatidylcholine (PtdCho) is recognized as a major structural building block of biological membranes and the precursor to diacylglycerol and eicosanoid second messengers following stimulation of cell surface receptors. The research will focus on CTP:phosphocholine cytidylyltransferase (CT), the enzyme that governs the rate of PtdCho biosynthesis, and the relationship between PtdCho metabolism, growth factor stimulation and cell cycle progression in a colony-stimulating factor 1 (CSF-1)-dependent murine macrophage cell line. Membrane phospholipid synthesis is a cell cycle-regulated process governed by the interaction between PtdCho synthesis and degradation. PtdCho degradation is regulated by growth factor stimulation in GI phase and PtdCho synthesis is controlled by periodic CT phosphorylation. PtdCho, in turn, influences cell cycle regulation. The inhibition of S phase PtdCho synthesis with an antineoplastic lysophosphatidylcholine analog leads to the arrest of BAC1.2F5 macrophage cells in G2 phase followed by apoptosis. This research demonstrates that PtdCho synthesis is an essential process inhibited by this unique class of anticancer drugs, thus defining their mechanism of action and identifying CT as a novel anticancer drug target. These data also reveal an interaction between PtdCho synthesis and the cell cycle machine that ensures the coordination of membrane formation with cell growth. The goals of the proposed project are to clarify the mechanistic details that underlie this regulatory loop. The experimental plan is organized around three specific aims that will address: 1) the role of CT phosphorylation at Ser-315, a major phosphorylation site in vivo, by cyclin-dependent protein kinases in the regulation of PtdCho metabolism, 2) the mechanism for the inactivation of CT and PtdCho synthesis in CSF-1- deprived cells, and 3) the regulation of the cell cycle by membrane PtdCho content and the role of CT in CSF-1-stimulated PtdCho degradation. These experiments are designed to generate new information that will contribute to the understanding of membrane phospholipid formation during entry, transit and exit from the cell cycle. Since there is only a single CT gene and protein, the proposed research on this ubiquitous regulator of phospholipid synthesis is directly relevant to other mammalian cell systems. Defining the role of CT and PtdCho in cell growth and function will provide important information that will be useful in the development of new approaches to exploiting CT and other enzymes in the CDP-choline pathway as therapeutic targets.