Campbell K S, Cambier J C
Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
EMBO J. 1990 Feb;9(2):441-8. doi: 10.1002/j.1460-2075.1990.tb08129.x.
T and B lymphocyte antigen receptors exhibit single transmembrane spanning regions and very short, three to five amino acid, C-terminal cytoplasmic tails. Ligation of these receptors leads, apparently through GTP binding protein activation, to rapid stimulation of a polyphosphoinositide specific phosphodiesterase (PPI-PDE). T lymphocyte antigen receptors (alpha beta) are coupled to PPI-PDE via a receptor associated complex of membrane proteins, designated CD3. Although an analogous transducer complex is presumed to exist in B cells, no such structure has been defined. We utilized in vitro [32P]phosphorylation to identify and characterize a membrane immunoglobulin (mIg) associated phosphoprotein complex which appears to represent a B cell analog of CD3. The phosphoprotein complex consists of three N-glycosylated polypeptides which occur as disulfide linked dimers, non-covalently associated with mIg. The complex associated with mIgM (pp32, pp34 and pp37 subunits) differs from that associated with mIgD (pp33, pp34 and pp37 subunits), and the isotype specific phosphoprotein (pp32 or pp33) appears to exist as a disulfide linked heterodimer with either pp34 or pp37. Aluminum fluoride stimulates phosphorylation of all of the subunits, and at least one of the proteins is phosphorylated on a tyrosine residue(s).
T和B淋巴细胞抗原受体具有单个跨膜区以及非常短的、由三到五个氨基酸组成的C末端胞质尾。这些受体的连接显然通过GTP结合蛋白激活，导致多磷酸肌醇特异性磷酸二酯酶（PPI-PDE）的快速刺激。T淋巴细胞抗原受体（αβ）通过一种称为CD3的膜蛋白相关复合物与PPI-PDE偶联。虽然推测B细胞中存在类似的转导复合物，但尚未确定这样的结构。我们利用体外[32P]磷酸化来鉴定和表征一种膜免疫球蛋白（mIg）相关的磷蛋白复合物，它似乎代表了CD3的B细胞类似物。该磷蛋白复合物由三种N-糖基化多肽组成，它们以二硫键连接的二聚体形式存在，与mIg非共价结合。与mIgM相关的复合物（pp32、pp34和pp37亚基）与与mIgD相关的复合物（pp33、pp34和pp37亚基）不同，并且同种型特异性磷蛋白（pp32或pp33）似乎以与pp34或pp37形成的二硫键连接的异二聚体形式存在。氟化铝刺激所有亚基的磷酸化，并且至少有一种蛋白在酪氨酸残基上被磷酸化。
