Serine phosphorylation of FcγRI cytoplasmic domain directs lipid raft localization and interaction with protein 4.1G
Serine phosphorylation of FcγRI cytoplasmic domain directs lipid raft localization and interaction with protein 4.1G
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DOI：
10.1189/jlb.0711368
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发表时间：
2012-01-01
影响因子：
5.5
通讯作者：
Kimberly, Robert P.
中科院分区：
文献类型：
--
作者：
Gibson, Andrew W.;Li, Xinrui;Kimberly, Robert P.
高亲和力IgG受体（CD 64，Fc γ RI）具有几种特殊能力，包括TNF超家族的细胞表面B细胞活化因子（TNFSF 13 B）的受体刺激裂解。通过使用酵母双杂交系统，我们和其他人已经证明Fc γ RI与蛋白4.1G（EPB 41 L2）相互作用。我们的突变分析确定了Fc γ RI CY中两个必需的4.1G相互作用区域和蛋白4.1G C末端中的一个Fc γ RI相互作用位点。在此，我们探索了可能调节蛋白4.1G和Fc γ RI CY之间相互作用并影响Fc γ RI膜迁移率和功能的机制。我们表明，Fc γ RI CY在体外与蛋白4.1G相互作用，并且Fc γ RI在新鲜分离的人PBMC中与蛋白4.1G共免疫沉淀。通过使用免疫染色，我们表明Fc γ RI与未刺激的U937细胞中的蛋白4.1G共定位，其中Fc γ RI CY是组成性丝氨酸磷酸化的，但在Fc γ RI交联后发生显着的解偶联，表明磷酸化丝氨酸调节的相互作用。在体外，蛋白4.1G优先与CK 2-磷酸化Fc γ RI CY相互作用，与WT Fc γ RI相比，非磷酸化Fc γ RI突变体受体被排除在脂筏之外，表明蛋白4.1G在将磷酸化Fc γ RI靶向脂筏中起关键作用。这些数据与蛋白4.1G在维持脂筏中的Fc γ RI中的磷酸丝氨酸依赖性束缚作用一致，并提供了对Fc γ RI CY对受体信号传导的独特的基于磷酸丝氨酸的调节的见解。J. Leukoc. 91：97-103; 2012.
The high-affinity IgG receptor (CD64, Fc gamma RI) has several special capacities, including the receptor-stimulated cleavage of the cell surface B cell-activating factor of the TNF superfamily (TNFSF13B). With the use of the yeast two-hybrid system, we and others have shown that Fc gamma RI interacts with protein 4.1G (EPB41L2). Our mutational analyses identified two required 4.1G-interacting regions in the Fc gamma RI CY and one Fc gamma RI-interacting site in the C-terminus of protein 4.1G. Herein, we explore mechanism(s) that may regulate the interaction between protein 4.1G and Fc gamma RI CY and influence Fc gamma RI membrane mobility and function. We show that Fc gamma RI CY interacts with protein 4.1G in vitro and that Fc gamma RI co-immunoprecipitates protein 4.1G in freshly isolated human PBMC. With the use of immunostaining, we show that Fc gamma RI colocalizes with protein 4.1G in unstimulated U937 cells, in which the Fc gamma RI CY is constitutively serine-phosphorylated, but significant uncoupling occurs following Fc gamma RI cross-linking, suggesting phosphoserine-regulated interaction. In vitro, protein 4.1G interacted preferentially with CK2-phosphorylated Fc gamma RI CY, and compared with WT Fc gamma RI, a nonphosphorylatable Fc gamma RI mutant receptor was excluded from lipid rafts, suggesting a key role for protein 4.1G in targeting phosphorylated Fc gamma RI to rafts. These data are consistent with a phosphoserine-dependent tethering role for protein 4.1G in maintaining Fc gamma RI in lipid rafts and provide insight into the unique phosphoserine-based regulation of receptor signaling by Fc gamma RI CY. J. Leukoc. Biol. 91: 97-103; 2012.