Duchemin A M, Anderson C L
Department of Internal Medicine, Ohio State University College of Medicine, Columbus, OH 43210, USA.
J Immunol. 1997 Jan 15;158(2):865-71.
To characterize the functional macromolecular complex of the high affinity receptor for IgG (Fc gamma RI), we have undertaken the identification of the molecules associated with the ligand binding unit and its associated subunit, gamma-chain, in a monocyte cell line, U937. Comparison of the pattern of tyrosine-phosphorylated proteins that coprecipitate with anti-Fc gamma RI or anti-gamma-chain Abs after Fc gamma RI clustering suggests that, like other receptor systems, the different units of the receptor associate or recruit different elements of the signaling pathway. Syk associates preferentially with the gamma-chain subunit and not with Fc gamma RI itself. This association is dependent on receptor clustering and correlates with gamma-chain phosphorylation. The Src kinase Lyn is also part of the receptor complex. Lyn associates with both units of the receptor, and this association is independent of receptor engagement; however, the level of tyrosine phosphorylation of the kinase increases after Fc gamma RI clustering. Association of a 35-kDa phosphoprotein with the binding unit was also observed after receptor clustering. We further found that after Fc gamma RI clustering, tyrosine-phosphorylated Syk associates with Lyn. These data suggest that several levels of interaction occur between these molecules or that different pools of tyrosine kinases become activated after Fc gamma RI clustering.
为了表征IgG高亲和力受体（FcγRI）的功能性大分子复合物，我们已着手在单核细胞系U937中鉴定与配体结合单元及其相关亚基γ链相关的分子。FcγRI聚集后，与抗FcγRI或抗γ链抗体共沉淀的酪氨酸磷酸化蛋白模式的比较表明，与其他受体系统一样，受体的不同单元会结合或募集信号通路的不同元件。Syk优先与γ链亚基结合，而不与FcγRI本身结合。这种结合依赖于受体聚集，并与γ链磷酸化相关。Src激酶Lyn也是受体复合物的一部分。Lyn与受体的两个单元都结合，且这种结合不依赖于受体激活；然而，FcγRI聚集后，该激酶的酪氨酸磷酸化水平会增加。受体聚集后，还观察到一种35 kDa的磷蛋白与结合单元结合。我们进一步发现，FcγRI聚集后，酪氨酸磷酸化的Syk与Lyn结合。这些数据表明，这些分子之间存在多个相互作用层面，或者说FcγRI聚集后，不同池的酪氨酸激酶被激活。
