Szente B E, Subramaniam P S, Johnson H M
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611, USA.
J Immunol. 1995 Dec 15;155(12):5617-22.
The tyrosine kinase JAK2 is an integral part of the signal transduction pathways of a number of cytokines and growth factors, including IFN-gamma. Previously, we identified a species-nonspecific binding site for the C terminus of IFN-gamma, encompassed by IFN-gamma peptide IFN-gamma(95-133), on the membrane proximal region of the cytoplasmic domain of the IFN-gamma R alpha-chain. Using both a radioligand binding assay and coimmunoprecipitation with antireceptor antiserum, we were able to demonstrate specific interaction of JAK2 with the murine IFN-gamma R(MIR) alpha-chain. Furthermore, this interaction is increased by the addition of murine IFN-gamma or its C-terminal peptide, muIFN-gamma(95-133). We also identified two regions of the cytoplasmic domain of the receptor that interact with JAK2 using synthetic peptides of the MIR alpha-chain in receptor competition studies. These regions are encompassed by receptor peptide MIR(283-309), which is adjacent to the membrane proximal region at which the C terminus of IFN-gamma binds, and receptor peptide MIR(404-432), which lies near the C terminus of the receptor, encompassing a potentially important phosphorylation site. These data show site-specific interaction between JAK2 and IFN-gamma with the IFN-gamma R and have broader implications for the role of the IFN-gamma ligand in the IFN-gamma signal transduction pathway. Furthermore, the data support previous studies that demonstrated that intracellular IFN-gamma plays a role in cell activation.
酪氨酸激酶JAK2是包括干扰素-γ（IFN-γ）在内的多种细胞因子和生长因子信号转导途径的一个组成部分。此前，我们在IFN-γRα链胞质结构域的膜近端区域鉴定出一个IFN-γ C末端的物种非特异性结合位点，该位点由IFN-γ肽IFN-γ(95 - 133)包围。通过放射性配体结合试验以及与抗受体抗血清的共免疫沉淀，我们能够证明JAK2与小鼠IFN-γR（MIR）α链存在特异性相互作用。此外，添加小鼠IFN-γ或其C末端肽muIFN-γ(95 - 133)会增强这种相互作用。在受体竞争研究中，我们还使用MIRα链的合成肽鉴定出受体胞质结构域中与JAK2相互作用的两个区域。这些区域由受体肽MIR(283 - 309)包围，该肽与IFN-γ C末端结合的膜近端区域相邻，以及受体肽MIR(404 - 432)，其位于受体C末端附近，包含一个潜在的重要磷酸化位点。这些数据显示了JAK2与IFN-γR之间的位点特异性相互作用，并且对IFN-γ配体在IFN-γ信号转导途径中的作用具有更广泛的意义。此外，这些数据支持了先前的研究，即细胞内IFN-γ在细胞激活中发挥作用。
