Stephan V, Seibt A, Dukanovic D, Skasa M, Swaim W D, Berenstein E H, Siraganian R P, Wahn V
University Children's Hospital, Düsseldorf, Germany.
Mol Immunol. 1997 Feb;34(3):227-35. doi: 10.1016/s0161-5890(97)00026-6.
In rat basophilic leukemia 2H3 (RBL-2H3) cells, mAb AA4 binds to two derivatives of ganglioside GD1b that associate with the Src family kinase p53/56lyn and a serine kinase. Pre-incubation of cells with mAb AA4 blocks immunoglobulin E (IgE) mediated histamine release. In the present study we investigated the effect of incubation with mAb AA4 on signal transduction events. In addition to stimulation of the high affinity IgE receptor (Fc epsilonRI), cells were also activated by the calcium ionophore A23187 and the acetylcholine agonist carbachol in RBL-2H3 cells transfected with the G protein-coupled m3 muscarinic receptor. Incubation of cells with mAb AA4 in a dose-dependent manner inhibited the following Fc epsilonRI-induced signal transduction events: the increase of intracellular free calcium, phosphoinositol breakdown, tyrosine phosphorylation of proteins including the beta- of Fc epsilonRI and secretion. However, there was no inhibition of degranulation or of these biochemical events when cells were stimulated with calcium ionophore or activated via a G protein-coupled pathway. Our results demonstrate that mAb AA4 selectively blocks Fc epsilonRI-induced cell activation at a very early step upstream of receptor tyrosine phosphorylation. As mAb AA4 has previously been found to bind to gangliosides associated with Fc epsilonRI, inhibition of very early biochemical events may be due to interaction of mAb AA4 with the Fc epsilonRI induced signal transduction cascade at the receptor level.
在大鼠嗜碱性白血病2H3（RBL - 2H3）细胞中，单克隆抗体AA4与神经节苷脂GD1b的两种衍生物结合，这两种衍生物与Src家族激酶p53/56lyn和一种丝氨酸激酶相关。用单克隆抗体AA4对细胞进行预孵育可阻断免疫球蛋白E（IgE）介导的组胺释放。在本研究中，我们研究了用单克隆抗体AA4孵育对信号转导事件的影响。除了刺激高亲和力IgE受体（FcεRI）外，在用G蛋白偶联的m3毒蕈碱受体转染的RBL - 2H3细胞中，细胞还被钙离子载体A23187和乙酰胆碱激动剂卡巴胆碱激活。用单克隆抗体AA4以剂量依赖性方式孵育细胞可抑制以下FcεRI诱导的信号转导事件：细胞内游离钙增加、磷酸肌醇分解、包括FcεRIβ在内的蛋白质酪氨酸磷酸化以及分泌。然而，当用钙离子载体刺激细胞或通过G蛋白偶联途径激活细胞时，脱颗粒或这些生化事件没有受到抑制。我们的结果表明，单克隆抗体AA4在受体酪氨酸磷酸化上游的非常早期阶段选择性地阻断FcεRI诱导的细胞活化。由于先前已发现单克隆抗体AA4与与FcεRI相关的神经节苷脂结合，对非常早期生化事件的抑制可能是由于单克隆抗体AA4与FcεRI诱导的信号转导级联在受体水平的相互作用。
