The erythropoietin receptor transmembrane domain mediates complex formation with viral anemic and polycythemic gp55 proteins
The erythropoietin receptor transmembrane domain mediates complex formation with viral anemic and polycythemic gp55 proteins
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DOI：
10.1074/jbc.m302974200
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发表时间：
2003-10-31
影响因子：
4.8
通讯作者：
Henis, YI
中科院分区：
文献类型：
--
作者：
Constantinescu, SN;Keren, T;Henis, YI
促红细胞生成素受体（EpoR）的激活对于成熟红细胞的产生至关重要。鼠EpoR也可以被红细胞增多（P）脾病灶形成病毒（SFFV）的包膜蛋白gp 55-P激活。由于TM序列的差异，贫血（A）株SFFV的gp 55-A不能有效地激活EpoR。使用抗体介导的免疫荧光共修补，我们表明，大多数的EpoR形成异源寡聚体在细胞表面与gp 55-P，令人惊讶的是，与gp 55-A。EpoR TM结构域被gp 55-P和-A靶向，因为只有嵌合受体含有与gp 55蛋白寡聚化的EpoR TM序列。gp 55-P和gp 55-A在细胞表面上都是同源二聚体，如通过共修补所示。然而，当用TOXCAT细菌报告系统分析分离的TM结构域的同源相互作用时，只有gp 55-P的TM序列被二聚化。因此，gp 55蛋白的同源寡聚化不足以完全激活EpoR，并且需要TM区域中二聚体的正确构象。这得到了gp 55-A3 P（一种其TM结构域可以同源寡聚化的突变蛋白）完全激活EpoR的失败的支持。由于未配体的EpoR形成TM依赖性的，但无活性的同源二聚体，我们建议EpoR可以激活到不同程度的同源二聚体的gp 55蛋白，这取决于在TM区域的gp 55蛋白二聚体的构象。
Erythropoietin receptor (EpoR) activation is crucial for mature red blood cell production. The murine EpoR can also be activated by the envelope protein of the polycythemic (P) spleen focus forming virus (SFFV), gp55-P. Due to differences in the TM sequence, gp55 of the anemic (A) strain SFFV, gp55-A, cannot efficiently activate the EpoR. Using antibody-mediated immunofluorescence co-patching, we show that the majority of EpoR forms hetero-oligomers at the cell surface with gp55-P and, surprisingly, with gp55-A. The EpoR TM domain is targeted by gp55-P and -A, as only chimeric receptors containing EpoR TM sequences oligomerized with gp55 proteins. Both gp55-P and gp55-A are homodimers on the cell surface, as shown by co-patching. However, when the homomeric interactions of the isolated TM domains were assayed by TOXCAT bacterial reporter system, only the TM sequence of gp55-P was dimerized. Thus, homo-oligomerization of gp55 proteins is insufficient for full EpoR activation, and a correct conformation of the dimer in the TM region is required. This is supported by the failure of gp55-A3P, a mutant protein whose TM domain can homo-oligomerize, to fully activate EpoR. As unliganded EpoR forms TM-dependent but inactive homodimers, we propose that the EpoR can be activated to different extents by homodimeric gp55 proteins, depending on the conformation of the gp55 protein dimer in the TM region.