Kotenko S V, Izotova L S, Mirochnitchenko O V, Lee C, Pestka S
Department of Molecular Genetics and Microbiology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854-5635, USA.
Proc Natl Acad Sci U S A. 1999 Apr 27;96(9):5007-12. doi: 10.1073/pnas.96.9.5007.
Type I IFNs activate the Jak-Stat signal transduction pathway. The IFN-alpha receptor 1 (IFN-alphaR1) subunit and two splice variants of the IFN-alphaR2 subunit, IFN-alphaR2c and IFN-alphaR2b, are involved in ligand binding. All these receptors have been implicated in cytokine signaling and, specifically, in Stat recruitment. To evaluate the specific contribution of each receptor subunit to Stat recruitment we employed chimeric receptors with the extracellular domain of either IFN-gammaR2 or IFN-gammaR1 fused to the intracellular domains of IFN-alphaR1, IFN-alphaR2b, and IFN-alphaR2c. These chimeric receptors were expressed in hamster cells. Because human IFN-gamma exhibits no activity on hamster cells, the use of the human IFN-gamma receptor extracellular domains allowed us to avoid the variable cross-species activity of the type I IFNs and eliminate the possibility of contributions of endogenous type I IFN receptors into the Stat recruitment process. We demonstrate that Stat recruitment is solely a function of the IFN-alphaR2c intracellular domain. When chimeric receptors with the human IFN-gammaR1 extracellular domain and various human IFN-alpha receptor intracellular domains were expressed in hamster cells carrying the human IFN-gammaR2 subunit, only the IFN-alphaR2c subunit was capable of supporting IFN-gamma signaling as measured by MHC class I induction, antiviral protection, and Stat activation. Neither the IFN-alphaR2b nor the IFN-alphaR1 intracellular domain was able to recruit Stats or support IFN-gamma-induced biological activities. Thus, the IFN-alphaR2c intracellular domain is necessary and sufficient to activate Stat1, Stat2, and Stat3 proteins.
I型干扰素激活Jak-Stat信号转导通路。干扰素α受体1（IFN-αR1）亚基以及IFN-αR2亚基的两种剪接变体IFN-αR2c和IFN-αR2b参与配体结合。所有这些受体都与细胞因子信号传导有关，特别是与Stat募集有关。为了评估每个受体亚基对Stat募集的具体贡献，我们使用了嵌合受体，其将IFN-γR2或IFN-γR1的细胞外结构域与IFN-αR1、IFN-αR2b和IFN-αR2c的细胞内结构域融合。这些嵌合受体在仓鼠细胞中表达。由于人IFN-γ对仓鼠细胞无活性，使用人IFN-γ受体细胞外结构域使我们能够避免I型干扰素的可变跨物种活性，并消除内源性I型干扰素受体对Stat募集过程产生贡献的可能性。我们证明，Stat募集仅仅是IFN-αR2c细胞内结构域的功能。当在携带人IFN-γR2亚基的仓鼠细胞中表达具有人IFN-γR1细胞外结构域和各种人IFN-α受体细胞内结构域的嵌合受体时，通过MHC I类诱导、抗病毒保护和Stat激活测量，只有IFN-αR2c亚基能够支持IFN-γ信号传导。IFN-αR2b和IFN-αR1细胞内结构域均不能募集Stats或支持IFN-γ诱导的生物学活性。因此，IFN-αR2c细胞内结构域对于激活Stat1、Stat2和Stat3蛋白是必要且充分的。
