免疫球蛋白介导的信号转导是通过Igα和Igβ实现的。
Signal transduction by immunoglobulin is mediated through Ig alpha and Ig beta.
作者信息
Sanchez M, Misulovin Z, Burkhardt A L, Mahajan S, Costa T, Franke R, Bolen J B, Nussenzweig M
机构信息
Howard Hughes Medical Institute, Rockefeller University, New York, NY 10021.
出版信息
J Exp Med. 1993 Sep 1;178(3):1049-55. doi: 10.1084/jem.178.3.1049.
Immunoglobulin (Ig) antigen receptors are composed of a noncovalently-associated complex of Ig and two other proteins, Ig alpha and Ig beta. The cytoplasmic domain of both of these Ig associated proteins contains a consensus sequence that is shared with the signaling proteins of the T cell and Fc receptor. To test the idea that Ig alpha-Ig beta heterodimers are the signaling components of the Ig receptor, we have studied Ig mutations that interfere with signal transduction. We find that specific mutations in the transmembrane domain of Ig that inactivate Ca2+ and phosphorylation responses also uncouple IgM from Ig alpha-Ig beta. These results define amino acid residues that are essential for the assembly of the Ig receptor. Further, receptor activity can be fully reconstituted in Ca2+ flux and phosphorylation assays by fusing the cytoplasmic domain of Ig alpha with the mutant Igs. In contrast, fusion of the cytoplasmic domain of Ig beta to the inactive Ig reconstitutes only Ca2+ responses. Thus, Ig alpha and Ig beta are both necessary and sufficient to mediate signal transduction by the Ig receptor in B cells. In addition, our results suggest that Ig alpha and Ig beta can activate different signaling pathways.
免疫球蛋白（Ig）抗原受体由Ig与另外两种蛋白质（Igα和Igβ）通过非共价结合形成的复合物组成。这两种与Ig相关的蛋白质的胞质结构域都含有一个与T细胞和Fc受体的信号蛋白共有的共有序列。为了验证Igα-Igβ异二聚体是Ig受体的信号传导成分这一观点，我们研究了干扰信号转导的Ig突变。我们发现，Ig跨膜结构域中的特定突变会使Ca2+和磷酸化反应失活，同时也会使IgM与Igα-Igβ解偶联。这些结果确定了Ig受体组装所必需的氨基酸残基。此外，通过将Igα的胞质结构域与突变型Ig融合，在Ca2+通量和磷酸化测定中可以完全重建受体活性。相比之下，将Igβ的胞质结构域与无活性的Ig融合只能重建Ca2+反应。因此，Igα和Igβ对于介导B细胞中Ig受体的信号转导既是必要的也是充分的。此外，我们的结果表明Igα和Igβ可以激活不同的信号通路。
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