REGULATION OF MEMBRANE BIOSYNTHESIS BY CSF-1

这项研究计划的长期目标是为 了解如何关键代谢途径所需的 造血细胞的增殖受生长因子调节。 我们的研究将集中在集落刺激因子1（CSF-1）， 增殖所需的造血生长因子， 单核吞噬细胞的分化和存活。 我们选择 以BAC1.2F5细胞系为模型巨噬细胞系统。 这些细胞 表现出生长和生存力的绝对CSF-1需求， 短暂剥夺时细胞周期的早期G1期阻滞 的CSF-1，从而允许研究细胞周期特异性代谢 改变。 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 着重于膜磷脂生物合成的调节， BAC 1.2F5细胞中的CSF-1和cAMP。 虽然很明显，细胞必须 增加细胞周期中磷脂形成的净速率 为了产生子细胞，很少有关于 细胞周期和磷脂形成之间的关系。 的 BAC 1.2F5磷脂生物合成途径中的速率控制酶 CTP：磷酸胆碱胞苷酰转移酶，我们的工作假设是 胞苷酰转移酶活性的调节是 膜磷脂生物合成受CSF-1和cAMP调节。 胞苷酰转移酶在非分裂细胞中已被广泛研究 其酶活性通过与膜结合而增强， 通过磷酸化减弱。 我们有证据表明 胞苷酰转移酶mRNA水平的因子调节，说明了 对该键的细胞活动的额外控制水平 酵素 定义CSF1和cAMP在调节 BAC1.2F5细胞中的胞苷酰转移酶催化活性将有助于 我们对巨噬细胞生长协调机制的理解 和膜生物发生。 该项目围绕三个具体的 目的：（1）研究CTP：磷酸胆碱（CTP：Phosphocholine）的表达调控 通过CSF-1检测胞苷酰转移酶mRNA的表达， 胞苷酰转移酶的翻译后修饰与 细胞周期中膜形成的速率;和（3）为了定义 胞苷酰转移酶在cAMP抑制巨噬细胞中的作用 膜磷脂生物合成

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.