Signal transduction in IgE receptor transfected mast cells

我们建立了IgE受体转染的小鼠肥大细胞瘤P815细胞。IgE受体由三种类型的多肽组成；一个结合ige的α亚基，一个β亚基和两个二硫化物连接的α亚基。制备了三种P815转染体；引入编码全部三个亚基的cdna (Wt)，引入编码全部α和γ亚基和c端缺失β亚基的cdna (beta cd)，引入编码全部α和β亚基和c端缺失γ亚基的cdna （gamma cd）。在Wt细胞中，IgE受体的内吞作用、IgE受体β亚基和γ亚基酪氨酸磷酸化、Lyn和Syk激酶以及42k蛋白增加。胞质Ca^<2+>浓度（[Ca^<2+>]i）和细胞表面CD63抗原表达增加。而在β - cd和γ - cd细胞中，IgE受体的内吞作用、上述蛋白的酪氨酸磷酸化、[Ca^<2+>]i增加，cd63抗原在细胞上的表达没有或很少增加。在Wt细胞中，CD63抗原在细胞表面的表达大部分被herbyycin a预处理阻断，CD63抗原的表面表达反映了RBL-2H3细胞的脱粒。因此，这些结果表明，β和γ亚基的c端胞质结构域的酪氨酸磷酸化对于IgE受体内溶胞、[Ca^<2+>]i增加和脱粒是必需的。

We estabilshed the IgE receptor transfected-mouse mastocytoma P815 cells. The IgE receptors are composed of three types of polypeptides ; an IgE-biniding alpha subunit, a beta subunit, and two disulfide-linked gamma subunits. Three types of P815 transfectant were made ; cDNAs coding for each of whole three subunits were introduced (Wt) , cDNAs coding for whole alpha and gamma subunit and C-terminal depleted beta subunit were introduced (beta cd), cDNAs coding for whole alpha and beta subunit and C-terminal depleted gamma subunit were introduced (gamma cd). In Wt cells, endocytosis fo IgE receptors, tyrosine phosphorylation of beta and gamma subunit of IgE receptors, Lyn and Syk kinases and 42k protein ware increased. And the cytosolic Ca^<2+> concentration ([Ca^<2+>]i) and CD63 antigen expression on the cell surfaces were increased. However, in beta cd and gamma cd cells, the endocytosis of IgE receptor, tyrosine phosphorylation of above proteins, [Ca^<2+>]i increase and CD 63 antigen expression on the cells were not or little increased. In Wt cells, CD63 antigen expression on the cell surfaces was mostly blocked by the preteatment of herbimycin A.The surface expression of CD63 antigen reflected the degranulation in RBL-2H3 cells. Therefore, these results suggested that tyrosing phosphorylation of the C-terminal cytoplasmic domains of beta and gamma subunits was essential for IgE receptor endo cytosis, [Ca^<2+>]i increase and degranulation.