Marquardt D L, Alongi J L, Walker L L
Department of Medicine, University of California, San Diego, La Jolla 92093, USA.
J Immunol. 1996 Mar 1;156(5):1942-5.
Phosphatidylinositol 3-kinase (PI3-kinase) activity has been shown to be important in cellular signaling via receptors associated with tyrosine kinases and receptors coupled to small or heterotrimeric G proteins. The importance of this activity in mast cell degranulation, leukotriene C4 generation, and IL-6 production was examined in mouse bone marrow-derived mast cells stimulated by high affinity IgE receptor cross-linking, direct influx of calcium, and/or adenosine receptor agonist exposure. Wortmannin, a fungal metabolite that at nanomolar concentrations inhibits PI3-kinase relatively specifically, blocked the release of granule-associated mast cell mediators independent of the secretory stimulus used. This inhibition was most prominent after a 2- to 5-min preincubation with wortmannin and was equally effective in cells additionally treated with exogenous N-ethylcarboxamidoadenosine to potentiate preformed mediator release. Mast cell production of leukotriene C4 20 min after activation or IL-6 16 h after activation was unaffected by up to 100 nM of wortmannin exposure. Mast cells preincubated with wortmannin failed to develop the classic electronmicroscopic evidence of granule swelling and fusion, increased membrane ruffling, or exocytosis upon Ag challenge. Activation of PI3-kinase appears to be critical for mast cell degranulation but is not required for arachidonic acid metabolism or cytokine production to occur. Furthermore, the inhibition of mast cell secretion by wortmannin is not stimulus specific but is evident for both IgE receptor cross-linking and direct calcium influx.
磷脂酰肌醇3激酶（PI3激酶）活性已被证明在通过与酪氨酸激酶相关的受体以及与小G蛋白或异源三聚体G蛋白偶联的受体进行的细胞信号传导中起重要作用。在通过高亲和力IgE受体交联、钙直接内流和/或腺苷受体激动剂暴露刺激的小鼠骨髓来源肥大细胞中，研究了该活性在肥大细胞脱颗粒、白三烯C4生成和IL-6产生中的重要性。渥曼青霉素是一种真菌代谢产物，在纳摩尔浓度下相对特异性地抑制PI3激酶，它阻断了颗粒相关肥大细胞介质的释放，而与所使用的分泌刺激无关。在用渥曼青霉素预孵育2至5分钟后，这种抑制最为明显，并且在外源N-乙基羧酰胺腺苷处理以增强预先形成的介质释放的细胞中同样有效。激活后20分钟白三烯C4的产生或激活后16小时IL-6的产生不受高达100 nM渥曼青霉素暴露的影响。用渥曼青霉素预孵育的肥大细胞在受到抗原刺激时未能出现颗粒肿胀和融合、膜皱褶增加或胞吐作用的经典电子显微镜证据。PI3激酶的激活似乎对肥大细胞脱颗粒至关重要，但花生四烯酸代谢或细胞因子产生并不需要它。此外，渥曼青霉素对肥大细胞分泌的抑制不是刺激特异性的，在IgE受体交联和直接钙内流中均很明显。
