MECHANISM OF PHORBOL ESTER-INDUCED LIPID METABOLISM

拟议的研究涉及定义近端细胞内事件 参与促进肿瘤的佛波醇酯的作用。 具体地说， 花生四烯酸释放的生化机制， 将使用GH3大鼠垂体研究磷脂酰胆碱代谢 细胞 尽管已经提出，刺激磷脂酶 A2和磷脂酶C分别是这些事件的原因， 缺乏确凿的证据。 这些事件很重要，因为 来自许多细胞类型的累积证据表明：1）花生四烯酸 和/或代谢物可介导肿瘤促进，和2）磷脂酰胆碱 代谢似乎与佛波酯作用特别相关。 GH3细胞为这些研究提供了极好的模型，因为1）它们是 允许明确分配变化的同质细胞群 2）对蛋白激酶C的广泛研究， 推定的佛波酯受体已经在这些细胞中进行。 关于完整细胞研究中涉及的酶反应的建议 将在亚细胞级分中得到证实。 无论是蛋白激酶C还是 佛波醇酯的另一种细胞受体介导这些事件， 直接在粗制和纯化的膜中研究。 的影响 将二酰基甘油与佛波酯对花生四烯酸的作用进行比较 释放和磷脂酰胆碱代谢、细胞增殖和蛋白质 磷酸化 花生四烯酸作为细胞内 评价佛波醇酯和/或甘油二酯作用介质。 这些研究将进一步加深我们对生物化学的理解。 参与佛波酯诱导的花生四烯酸释放的机制， 磷脂酰胆碱代谢 此外，重要的是，这些 对佛波酯作用中近端细胞内事件的研究可能有助于 阐明某些肿瘤形成的过程。

The proposed research involves defining proximal intracellular events involved in the action of tumor-promoting phorbol esters. Specifically, the biochemical mechanisms of arachidonic acid release and phosphatidylcholine metabolism will be investigated using GH3 rat pituitary cells. Although it has been suggested that stimulation of a phospholipase A2 and phospholipase C, respectively are causative in these events, conclusive evidence is lacking. These events are important because accumulated evidence from many cell types suggests 1) that arachidonic acid and/or metabolites may mediate tumor promotion and 2) phosphatidylcholine metabolism appears specifically related to phorbol ester action. GH3 cells provide an excellent model for these studies because 1) they are a homogeneous cell population permitting unambiguous assignment of changes to a specific cell type and 2) extensive research into protein kinase C, the putative phorbol ester receptor has been performed in these cells. Suggestions as to the enzymic reactions involved from intact cell studies will be confirmed in subcellular fractions. Whether protein kinase C or another cellular acceptor for phorbol esters mediates these events will be studied directly in crude and purified membranes. The effects of diacylglycerols will be compared to phorbol esters on arachidonic acid release and phosphatidylcholine metabolism, cell proliferation, and protein phosphorylation. A potential role for arachidonic acid as an intracellular mediator of phorbol ester and/or diacylglycerol action will be assessed. These studies should further our understanding of the biochemical mechanisms involved in phorbol ester-induced arachidonic acid release and phosphatidylcholine metabolism. Furthermore, and importantly, these studies into proximal intracellular events in phorbol ester action may help elucidate processes involved in the development of some neoplasias.