Ha K S, Exton J H
Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0295.
J Cell Biol. 1993 Dec;123(6 Pt 2):1789-96. doi: 10.1083/jcb.123.6.1789.
alpha-Thrombin induced a change in the cell morphology of IIC9 fibroblasts from a semiround to an elongated form, accompanied by an increase in stress fibers. Incubation of the cells with phospholipase D (PLD) from Streptomyces chromofuscus and exogenous phosphatidic acid (PA) caused similar morphological changes, whereas platelet-derived growth factor (PDGF) and phorbol 12-myristate 13-acetate (PMA) induced different changes, e.g., disruption of stress fibers and cell rounding. alpha-Thrombin, PDGF, and exogenous PLD increased PA by 20-40%, and PMA produced a smaller increase. alpha-Thrombin and exogenous PLD produced rapid increases in the amount of filamentous actin (F-actin) that were sustained for at least 60 min. However, PDGF produced a transient increase of F-actin at 1 min and PMA caused no significant change. Dioctanoylglycerol was ineffective except at 50 micrograms/ml. Phospholipase C from Bacillus cereus, which increased diacylglycerol (DAG) but not PA, did not change F-actin content. Down-regulation of protein kinase C (PKC) did not block actin polymerization induced by alpha-thrombin. H-7 was also ineffective. Exogenous PA activated actin polymerization with a significant effect at 0.01 microgram/ml and a maximal increase at 1 microgram/ml. No other phospholipids tested, including polyphosphoinositides, significantly activated actin polymerization. PDGF partially inhibited PA-induced actin polymerization after an initial increase at 1 min. PMA completely or largely blocked actin polymerization induced by PA or PLD. These results show that PC-derived PA, but not DAG or PKC, activates actin polymerization in IIC9 fibroblasts, and indicate that PDGF and PMA have inhibitory effects on PA-induced actin polymerization.
α-凝血酶可使IIC9成纤维细胞的形态从半圆形变为细长形，并伴有应力纤维增加。用来自暗褐链霉菌的磷脂酶D（PLD）和外源性磷脂酸（PA）孵育细胞会引起类似的形态变化，而血小板衍生生长因子（PDGF）和佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）则诱导不同的变化，例如应力纤维破坏和细胞变圆。α-凝血酶、PDGF和外源性PLD使PA增加20%-40%，而PMA的增加幅度较小。α-凝血酶和外源性PLD使丝状肌动蛋白（F-肌动蛋白）的量迅速增加，并持续至少60分钟。然而，PDGF在1分钟时使F-肌动蛋白短暂增加，而PMA则未引起显著变化。二辛酰甘油无效，除非浓度为50微克/毫升。来自蜡状芽孢杆菌的磷脂酶C可增加二酰基甘油（DAG）但不增加PA，它不会改变F-肌动蛋白含量。蛋白激酶C（PKC）的下调不会阻断α-凝血酶诱导的肌动蛋白聚合。H-7也无效。外源性PA激活肌动蛋白聚合，在0.01微克/毫升时有显著作用，在1微克/毫升时达到最大增加。所测试的其他磷脂，包括多磷酸肌醇，均未显著激活肌动蛋白聚合。PDGF在1分钟最初增加后部分抑制PA诱导的肌动蛋白聚合。PMA完全或很大程度上阻断PA或PLD诱导的肌动蛋白聚合。这些结果表明，磷脂酰胆碱衍生的PA而非DAG或PKC激活IIC9成纤维细胞中的肌动蛋白聚合，并表明PDGF和PMA对PA诱导的肌动蛋白聚合具有抑制作用。
