Justement L B, Wienands J, Hombach J, Reth M, Cambier J C
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
J Immunol. 1990 May 1;144(9):3272-80.
We have measured Ca2+ mobilization in a panel of B lineage cell lines after stimulation with anti-Ig to assess whether membrane Ig transduces a functional signal in cells that are representative of immature, mature, or terminally differentiated stages. For these studies, three transfected cell lines which express the same IgM molecule (300-19 microns lambda 36/8, K46-17 microns lambda, and J558L microns lambda 3) as well as two lines expressing an identical IgD molecule (K46 delta m2.6 and J558L delta m8.8) were used. Cross-linking of membrane Ig on IgM+ or IgD+ lymphomas (K46-17 microns lambda or K46 delta m2.6) resulted in a Ca2+ mobilization response that is similar to that seen in mature, resting B cells. Both intracellular release and extracellular influx of Ca2+ were observed. In contrast, ligation of membrane Ig on an IgM+ pre-B cell line (300 - 19 microns lambda 36/8) induced extracellular influx of Ca2+ but no detectable intracellular release. Finally, cross-linking of membrane Ig on IgM+ or IgD+ plasmacytomas (J558L microns 3 or J558L delta m8.8) or an IgD+ B cell hybridoma (B1.8.delta 1) expressing an endogenous Ig gene, did not result in a detectable Ca2+ mobilization response. Importantly, stimulation of cells with the GTP-binding protein activator, aluminum fluoride, resulted in a comparable Ca2+ mobilization response in all cell lines. In view of the fact that aluminum fluoride induced a Ca2+ response in the terminally differentiated B cell lines, J558L microns 3, J558L delta m8.8, and B1.8.delta 1, it is likely that there is an alteration in the signal transduction cascade at some point proximal to GTP binding protein activation. This finding suggests that differentiation of the B cell is accompanied by the loss or alteration of one or more components that couple membrane Ig to subsequent signal transduction elements. Finally, it has previously been demonstrated that the IgM+ cell lines described above, express the recently described membrane Ig-associated protein, B34. Thus, it is apparent based on the fact that the J558L microns 3 cell line does not mobilize Ca2+ after stimulation with anti-Ig, that coexpression of B34 in association with membrane Ig does not constitute a functional receptor complex capable of activating GTP-binding proteins that in turn regulate Ca2+ mobilization.
我们在用抗 Ig 刺激一组 B 系细胞系后测量了 Ca2+动员情况，以评估膜 Ig 是否能在代表未成熟、成熟或终末分化阶段的细胞中传递功能性信号。在这些研究中，使用了三种表达相同 IgM 分子（300 - 19 微米 lambda 36/8、K46 - 17 微米 lambda 和 J558L 微米 lambda 3）的转染细胞系以及两种表达相同 IgD 分子（K46 delta m2.6 和 J558L delta m8.8）的细胞系。IgM+或 IgD+淋巴瘤（K46 - 17 微米 lambda 或 K46 delta m2.6）上膜 Ig 的交联导致 Ca2+动员反应，这与在成熟静止 B 细胞中观察到的反应相似。观察到了 Ca2+的细胞内释放和细胞外流入。相比之下，IgM+前 B 细胞系（300 - 19 微米 lambda 36/8）上膜 Ig 的连接诱导了 Ca2+的细胞外流入，但未检测到细胞内释放。最后，IgM+或 IgD+浆细胞瘤（J558L 微米 3 或 J558L delta m8.8）或表达内源性 Ig 基因的 IgD+B 细胞杂交瘤（B1.8.delta 1）上膜 Ig 的交联未导致可检测到的 Ca2+动员反应。重要的是，用 GTP 结合蛋白激活剂氟化铝刺激细胞在所有细胞系中导致了类似的 Ca2+动员反应。鉴于氟化铝在终末分化的 B 细胞系 J558L 微米 3、J558L delta m8.8 和 B1.8.delta 1 中诱导了 Ca2+反应，很可能在靠近 GTP 结合蛋白激活的某个点信号转导级联发生了改变。这一发现表明 B 细胞的分化伴随着将膜 Ig 与后续信号转导元件偶联的一个或多个成分的丧失或改变。最后，先前已证明上述 IgM+细胞系表达最近描述的膜 Ig 相关蛋白 B34。因此，基于 J558L 微米 3 细胞系在用抗 Ig 刺激后不能动员 Ca2+这一事实很明显，B34 与膜 Ig 的共表达并不构成能够激活进而调节 Ca2+动员的 GTP 结合蛋白的功能性受体复合物。
