Coorssen J R
Department of Pathology, McMaster University, Hamilton, Ontario, Canada.
Am J Physiol. 1996 Apr;270(4 Pt 1):C1153-63. doi: 10.1152/ajpcell.1996.270.4.C1153.
Numerous studies have identified phospholipase metabolites as membrane fusogens, and phospholipase D (PLD) (J.R. Coorssen and R.J. Haslam. FEBS Lett. 316: 170-174, 1993), C (PLC), and A2 (PLA2) activities correlate with secretion. Do these enzymes have essential or modulatory roles? This study confirms that secretion does not require Ca2+ or PLC (Coorssen et al. Cell Regul. 1: 1027-1041, 1990). Arachidonic acid (AA), phosphatidic acid (PA) and analogues, exogenous metabolites of PLA2 and PLD, were tested in electropermeabilized human platelets. AA potentiated guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S)-induced secretion, and eicosanoids were not essential. Endogenous [3H]AA formation correlated with GTP gamma S-induced secretion, and phorbol 12-myristate 13-acetate (PMA) promoted these effects. Inhibitors were used to probe phospholipase influences on secretion. Only PLD inhibitors blocked secretion. However, PMA blocked inhibition of protein kinase C (PKC) and secretion by quercetin, suggesting that PA formed by PLD supports PKC activation and GTP gamma S-induced secretion. Thus PA analogues had no effect alone but enhanced GTP gamma S-induced PKC activity and secretion. Slower PLD activation compared with secretion also indicates a nonessential role. This is the first report of a Ca(2+)-independent PLA2 activity in human platelets, use of quercetin as a PLD inhibitor, and dissociation of PLA2, PLC, and PLD activities from secretion. No major phospholipase activities are essential to the final steps in exocytosis, but modulatory roles are indicated.
众多研究已将磷脂酶代谢产物鉴定为膜融合剂，并且磷脂酶D（PLD）（J.R. 库森和R.J. 哈斯拉姆。《欧洲生物化学学会联合会快报》316: 170 - 174, 1993）、C（PLC）和A2（PLA2）的活性与分泌相关。这些酶具有关键作用还是调节作用呢？本研究证实分泌不需要Ca2+或PLC（库森等人。《细胞调控》1: 1027 - 1041, 1990）。在电通透处理的人血小板中测试了花生四烯酸（AA）、磷脂酸（PA）及其类似物，它们是PLA2和PLD的外源性代谢产物。AA增强了鸟苷5'-O-(3 - 硫代三磷酸)（GTPγS）诱导的分泌，并且类花生酸并非必不可少。内源性[3H]AA的形成与GTPγS诱导的分泌相关，佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）促进了这些效应。使用抑制剂来探究磷脂酶对分泌的影响。只有PLD抑制剂能阻断分泌。然而，PMA能阻断槲皮素对蛋白激酶C（PKC）的抑制和分泌，这表明PLD形成的PA支持PKC激活和GTPγS诱导的分泌。因此，PA类似物单独使用没有作用，但能增强GTPγS诱导的PKC活性和分泌。与分泌相比，PLD激活较慢也表明其并非关键作用。这是关于人血小板中不依赖Ca(2+)的PLA2活性、使用槲皮素作为PLD抑制剂以及PLA2、PLC和PLD活性与分泌解离的首次报道。没有主要的磷脂酶活性对于胞吐作用的最终步骤是必不可少的，但显示出具有调节作用。
