Song J, Jiang Y W, Foster D A
Department of Biological Sciences, Hunter College, City University of New York, New York 10021.
Cell Growth Differ. 1994 Jan;5(1):79-85.
An early response to epidermal growth factor in A431 cells is the generation of diglyceride, a physiological activator of protein kinase C. By differentially prelabeling cellular phospholipids with [3H]arachidonate and [3H]myristate, which are incorporated primarily into phosphatidylinositol and phosphatidylcholine, respectively, we have found that epidermal growth factor induces an increase in diglyceride levels from both phosphatidylinositol and phosphatidylcholine via distinct mechanisms and kinetics. The epidermal growth factor-induced increase in phosphatidylinositol-derived diglyceride was transient and peaked at 5 min. As diglyceride levels dropped, there was a corresponding increase in phosphatidic acid, suggesting that the diglyceride is efficiently converted to phosphatidic acid by a diglyceride kinase. In contrast, epidermal growth factor-induced increases in phosphatidylcholine-derived diglyceride peaked at 30 min and remained elevated for greater than 2 h. The epidermal growth factor-induced increases in phosphatidic acid detected in [3H]myristate-prelabeled cells paralleled the increase in diglyceride, suggesting that the phosphatidylcholine-derived diglyceride is produced from phosphatidic acid via a phosphatidic acid phosphatase. Consistent with this hypothesis, epidermal growth factor also induced a protein kinase C-independent phospholipase D activity that was specific for phosphatidylcholine. These data suggest that epidermal growth factor induces diglyceride production from phosphatidylinositol and phosphatidylcholine via two distinct mechanisms: a rapid and transient induction of diglyceride that likely involves phospholipase c-gamma-mediated hydrolysis of phosphatidylinositol-4,5-bisphosphate and a slower, more sustained induction of diglyceride via a phospholipase D-mediated hydrolysis of phosphatidylcholine to produce phosphatidic acid, which is then converted to diglyceride by a phosphatidic acid phosphatase.(ABSTRACT TRUNCATED AT 250 WORDS)
A431细胞对表皮生长因子的早期反应是生成甘油二酯，它是蛋白激酶C的一种生理激活剂。通过分别用[3H]花生四烯酸和[3H]肉豆蔻酸对细胞磷脂进行差异预标记，它们主要分别掺入磷脂酰肌醇和磷脂酰胆碱，我们发现表皮生长因子通过不同的机制和动力学，使磷脂酰肌醇和磷脂酰胆碱的甘油二酯水平均升高。表皮生长因子诱导的磷脂酰肌醇衍生的甘油二酯增加是短暂的，在5分钟时达到峰值。随着甘油二酯水平下降，磷脂酸相应增加，这表明甘油二酯被甘油二酯激酶有效地转化为磷脂酸。相比之下，表皮生长因子诱导的磷脂酰胆碱衍生的甘油二酯在30分钟时达到峰值，并在2小时以上保持升高。在[3H]肉豆蔻酸预标记的细胞中检测到的表皮生长因子诱导的磷脂酸增加与甘油二酯的增加平行，这表明磷脂酰胆碱衍生的甘油二酯是通过磷脂酸磷酸酶由磷脂酸产生的。与该假设一致，表皮生长因子还诱导了一种不依赖蛋白激酶C的磷脂酶D活性，该活性对磷脂酰胆碱具有特异性。这些数据表明，表皮生长因子通过两种不同机制诱导磷脂酰肌醇和磷脂酰胆碱产生甘油二酯：一种是快速且短暂的甘油二酯诱导，可能涉及磷脂酶c-γ介导的磷脂酰肌醇-4,5-二磷酸水解；另一种是通过磷脂酶D介导的磷脂酰胆碱水解产生磷脂酸，然后由磷脂酸磷酸酶将其转化为甘油二酯，从而进行较慢且更持久的甘油二酯诱导。（摘要截断于250字）
