REGULATION OF MEMBRANE BIOSYNTHESIS BY CSF-1

这项研究计划的长期目标是为 了解关键代谢途径是如何需要的 造血细胞的增殖受生长因子的调节。 我们的研究将集中在集落刺激因子1(CSF-1)，a 增殖所需的造血生长因子， 单核巨噬细胞的分化和存活。我们已经选择了 以BAC1.2F5细胞系为模型巨噬细胞系统。这些细胞 表现出绝对的生长和生存能力所需的CSF-1，以及 短暂剥夺时细胞周期的早期G1期停滞 因此，可以研究细胞周期特异性代谢。 改装。与正常巨噬细胞一样，BAC1.2F5细胞的增殖是 被增加细胞内cAMP的配体阻断。我们的研究计划 重点介绍了两者对膜磷脂生物合成的调节作用 BAC1.2F5细胞中的cAMP和CSF-1的表达。虽然很明显细胞必须 增加它们在细胞周期中形成磷脂的净速率 为了产生子代细胞，几乎没有关于 细胞周期与磷脂形成的关系。这个 BAC1.2F5磷脂生物合成途径中的速率控制酶 是CTP：磷酸胆碱胞苷转移酶，我们的工作假设是 胞苷转移酶活性的调节是其主要机制。 其中膜磷脂的生物发生受CSF-1和cAMP的调控。 胞苷转移酶在非分裂细胞中得到了广泛的研究。 并且它的酶活性通过与膜和 通过磷酸化而减弱。我们已经产生了增长的证据 胞苷酰转移酶mRNA水平的因子调节，说明了 对此键的蜂窝活动的额外控制级别 酵素。明确CSF1和CAMP在治理中的作用 胞苷转移酶在BAC1.2F5细胞中的催化活性将有所贡献 对于我们对协调巨噬细胞生长的机制的理解 和膜生物发生。该项目围绕三个具体的 目的：(1)研究CTP：磷胆碱的调控表达 胞苷酰转移酶mRNA与脑脊液-1的关系；(2)确定两者之间的关系 胞苷酰转移酶的翻译后修饰与 在细胞周期中的膜形成速率；和(3)定义 胞苷转移酶在抑制巨噬细胞cAMP中的作用 膜磷脂的生物发生。

The long-term goal of this research plan is to contribute to the understanding of how key metabolic pathways required for the proliferation of hematopoietic cells are regulated by growth factors. Our investigations will center on colony-stimulating factor 1 (CSF-1), a hematopoietic growth factor required for the proliferation, differentiation and survival of mononuclear phagocytes. We have selected the BAC1.2F5 cell line as the model macrophage system. These cells exhibit an absolute CSF-1 requirement for both growth and viability and arrest in the early G1 phase of the cell cycle when transiently deprived of CSF-1, thus permitting investigations of cell cycle-specific metabolic alterations. Like normal macrophages, BAC1.2F5 cell proliferation is blocked by ligands that increase intracellular cAMP. Our research plan focuses on the regulation of membrane phospholipid biosynthesis by both CSF-1 and cAMP in BAC1.2F5 cells. While it is apparent that cells must increase their net rate of phospholipid formation during the cell cycle to produce daughter cells, little information is available on the relationship between the cell cycle and phospholipid formation. The rate-controlling enzyme in the BAC1.2F5 phospholipid biosynthetic pathway is CTP:phosphocholine cytidylyltransferase, and our working hypothesis is that modulation of cytidylyltransferase activity is the major mechanism by which membrane phospholipid biogenesis is regulated by CSF-1 and cAMP. Cytidylyltransferase has been extensively studied in nondividing cells and its enzymatic activity is enhanced by association with membranes and attenuated by phosphorylation. We have generated evidence for growth factor regulation of cytidylyltransferase mRNA levels, illustrating an additional level of control over the cellular activity of this key enzyme. Defining the role of CSF1 and cAMP in governing cytidylyltransferase catalytic activity in BAC1.2F5 cells will contribute to our understanding of the mechanisms that coordinate macrophage growth and membrane biogenesis. The project is organized around three specific aims: (1) To characterize the regulated expression of CTP:phosphocholine cytidylyltransferase mRNA by CSF-1; (2) To determine the relationship between post-translational modifications of cytidylyltransferase and the rate of membrane formation during the cell cycle; and (3) To define the role of cytidylyltransferase in the cAMP inhibition of macrophage membrane phospholipid biogenesis.