REGULATION OF PGHS-2 SYNTHESIS--ROLE OF LIPID MEDIATORS

我们的长期目标是确定前列腺素合成的作用 细胞生长控制。 最近的几项研究表明， 前列腺素内过氧化物合酶2型（PGHS-2）在 细胞内稳态 PGHS-2基因的缺失导致严重的 小鼠肾脏病理学。 相反，PGHS-2的过表达导致 细胞凋亡的抗性，这可能有助于致癌作用。 这些观察结果提出了解释 抑制前列腺素合成减少癌症的观察 人类的风险。 为了实现这一长期目标，我们将确定 脂质介质在前列腺素合成调节中的作用。 在我们以前的研究中，我们使用了Madin-Darby犬肾细胞， 研究前列腺素合成对肿瘤促进剂的反应 12-O-十四酰基-佛波醇-13-乙酸酯（TPA）。 我们发现TPA 通过磷脂酶D（PLD）刺激磷脂酸（PA）产生。 在TPA刺激的细胞中，PLD产生的PA是膜 Raf-1和PGHS-2基因表达的诱导。 在 相反，表皮生长因子对PGHS-2的诱导作用并不 依赖于PLD或蛋白激酶C（PKC）。 这些数据表明 存在导致PGHS-2诱导的不同途径。 之一 途径显然需要PKC、PLD和Raf-1。 另一途径 既不需要PKC也不需要PLD，但可能需要Raf-1或类似激酶 活动 为了进一步确定控制PGHS-2的这些途径， 综合我们将追求以下具体目标：1）确定 磷脂酶D在蛋白激酶C依赖性信号传导中的作用， 2)确定Raf-1在前列腺素控制中的作用 合成. 这些研究将使我们更好地了解 前列腺素合成的控制，并导致进一步的研究 PGHS-2在生长控制中的作用。 此外，新目标 治疗干预应该变得明显，可以用来 制定更具选择性的治疗策略， 比目前的不良影响。

Our long-term goal is to determine the role of prostaglandin synthesis in cellular growth control. Several recent studies indicate the importance of prostaglandin endoperoxide synthase, type 2 (PGHS-2) in cellular homeostasis. Deletion of the PGHS-2 gene results in severe renal pathology in mice. In contrast, overexpression of PGHS-2 results in resistance to apoptosis which may contribute to carcinogenesis. These observations suggest potential mechanisms to explain the observation that inhibition of prostaglandin synthesis decreases cancer risk in humans. To approach this long-term goal we will determine the role of lipid mediators in the regulation of prostaglandin synthesis. In our previous studies, we have used the Madin-Darby canine kidney cell line to study prostaglandin synthesis in response to the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). We find that TPA stimulates phosphatidic acid (PA) production by phospholipase D (PLD). In TPA-stimulated cells, the PA produced by PLD is required for membrane association of Raf-1 and for induction of PGHS-2 gene expression. In contrast, induction of PGHS-2 by epidermal growth factor is not dependent on PLD or protein kinase C (PKC). These data indicate that there are distinct pathways that result in PGHS-2 induction. One of the pathways apparently requires PKC, PLD and Raf-1. Another pathway requires neither PKC nor PLD but may require Raf-1 or a similar kinase activity. To further define these pathways for the control of PGHS-2 synthesis we will pursue the following specific aims: 1) to determine the role of phospholipase D in protein kinase C-dependent signalling and 2) to define the role of Raf-1 in the control of prostaglandin synthesis. Together these studies will give us a better understanding of the control of prostaglandin synthesis and lead to further studies of the role of PGHS-2 in growth control. In addition, new targets for therapeutic intervention should become apparent that can be used to develop treatment strategies that are more selective and have less adverse effects than those currently available.