Nakatani Y, Murakami M, Kudo I, Inoue K
Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
J Immunol. 1994 Jul 15;153(2):796-803.
We have reported previously that cultured mast cells (MC) express three discrete phospholipases A2 (PLA2s), one of which corresponds to arachidonoyl-preferential cytosolic PLA2 (cPLA2). In the present study, we investigated the possible role of cPLA2 in eicosanoid synthesis by activating mouse bone marrow-derived mast cells (BMMC) through cross-linking of the high affinity IgE receptor (Fc epsilon RI) with a specific Ag. BMMC released arachidonic acid within 2 min after Fc epsilon RI cross-linking. A rapid, transient phosphorylation of cPLA2 was observed after Fc epsilon RI cross-linking, reaching the maximum within 2 min, and accompanied by an increase of cPLA2 activity in the cell lysate. Exposure of BMMC to the IgE-Ag for longer periods resulted in a time-dependent increase of the cPLA2 protein. The increase was detected within 10 h after stimulation and reached the maximum within 30 h. Dexamethasone inhibited the Ag-stimulated cPLA2 induction significantly. cPLA2 activity in cells stimulated for 24 h was increased significantly, and suppressed in cells treated with dexamethasone. When the cells were exposed to IgE-Ag for 36 h and then challenged with a secondary agonist, thrombin, arachidonate release was augmented significantly in comparison with cells without the Ag pretreatment. Thus, cPLA2 activation in BMMC by short term exposure to the Ag might be regulated by post-Fc epsilon RI modification (phosphorylation) of pre-existing enzyme, whereas that observed after long term exposure might be explained by the increase in cPLA2 protein.
我们先前曾报道，培养的肥大细胞（MC）表达三种不同的磷脂酶A2（PLA2s），其中一种对应于花生四烯酰优先的胞质磷脂酶A2（cPLA2）。在本研究中，我们通过用特异性抗原交联高亲和力IgE受体（FcεRI）激活小鼠骨髓来源的肥大细胞（BMMC），研究了cPLA2在类花生酸合成中的可能作用。FcεRI交联后2分钟内，BMMC释放花生四烯酸。FcεRI交联后观察到cPLA2迅速、短暂的磷酸化，在2分钟内达到最大值，并伴随着细胞裂解物中cPLA2活性的增加。BMMC长时间暴露于IgE-抗原导致cPLA2蛋白随时间依赖性增加。刺激后10小时内检测到增加，30小时内达到最大值。地塞米松显著抑制抗原刺激的cPLA2诱导。刺激24小时的细胞中cPLA2活性显著增加，用地塞米松处理的细胞中cPLA2活性受到抑制。当细胞暴露于IgE-抗原36小时，然后用二次激动剂凝血酶刺激时，与未进行抗原预处理的细胞相比，花生四烯酸释放显著增加。因此，短期暴露于抗原时BMMC中cPLA2的激活可能受预先存在的酶的FcεRI修饰后（磷酸化）调节，而长期暴露后观察到的激活可能由cPLA2蛋白增加来解释。
