Pribluda V S, Metzger H
J Biol Chem. 1987 Aug 25;262(24):11449-54.
Aggregation of the receptor with high affinity for immunoglobulin E (IgE) in rat basophilic leukemia cells leads to a calcium-dependent and a calcium-independent hydrolysis of phosphoinositides. The increase in the levels of inositol phosphates induced in the absence of calcium is only 25% of that observed with 1 mM Ca2+. The inositol phosphates reach a new steady state level 2 min after stimulation in EGTA, whereas with calcium they continue to increase up to 15 min. A similar response is observed when the receptors are aggregated due to the interaction of bound IgE with antigen or with anit-IgE, or by the binding of IgE cross-linked chemically. The antigen-mediated response is inhibited by hapten and disruption of such antigen-antibody aggregates late after stimulation leads to a rapid decline in the levels of the inositol phosphates to basal values. Separation of the inositol phosphates by Dowex columns shows that there is a fast rise in inositol trisphosphate which peaks at 15 s and slowly declines to a lower plateau within 2 min. Analysis by high pressure liquid chromatography reveals a 5-fold increase in the levels of inositol 1,4,5-trisphosphate in less than 10 s after stimulation, which precedes any major change in the other inositol phosphates. Aggregation of the receptor in the absence of external calcium induces a transient increase in cytoplasmic calcium which reaches a maximum of approximately 25 nM over basal levels after activation. The onset of the rise in Ca2+ lags after the initial rise in the inositol 1,4,5-trisphosphate.
大鼠嗜碱性白血病细胞中对免疫球蛋白E（IgE）具有高亲和力的受体聚集会导致磷酸肌醇的钙依赖性和钙非依赖性水解。在无钙条件下诱导产生的肌醇磷酸水平增加量仅为1 mM Ca2+时所观察到的25%。在EGTA中刺激2分钟后，肌醇磷酸达到新的稳态水平，而在有钙的情况下，它们会持续增加直至15分钟。当受体由于结合的IgE与抗原或抗IgE相互作用而聚集，或通过化学交联的IgE结合而聚集时，会观察到类似的反应。抗原介导的反应受到半抗原的抑制，刺激后晚期此类抗原-抗体聚集体的破坏会导致肌醇磷酸水平迅速下降至基础值。用Dowex柱分离肌醇磷酸表明，肌醇三磷酸迅速升高，在15秒时达到峰值，并在2分钟内缓慢下降至较低的平稳状态。高压液相色谱分析显示，刺激后不到10秒，肌醇1,4,5-三磷酸水平增加了5倍，这先于其他肌醇磷酸的任何重大变化。在无细胞外钙的情况下受体聚集会诱导细胞质钙的短暂增加，激活后其最高比基础水平高出约25 nM。Ca2+升高的起始滞后于肌醇1,4,5-三磷酸的初始升高。
