TYK2 AND IFNAR1 IN INTERFERON ALPHA SIGNALING

JAK/STAT信号级联在细胞表面上的配体结合和细胞核中的基因转录之间提供了相对简单和直接的联系。这些途径介导对调节细胞生长、分化和效应子功能的不同多肽配体组的应答。最佳表征的JAK/STAT信号传导级联之一是由干扰素-α（IFN α）刺激的途径。许多实验室对这种信号转导级联的广泛研究提供了对调节IFN α诱导的基因转录的初始分子事件的基本理解，并建立了研究其他JAK-STAT途径的范例。在本基金的上一个学期，我们已经探索了这个级联反应中各种组分之间的分子相互作用：Tyk 2酪氨酸激酶，IFNaR 1受体亚基，以及Stat 1和Stat 2转录因子。特别是：i）鉴定和表征Tyk 2激酶-IFNaR 1受体复合物; ii）鉴定和表征IFNaR 1上的配体诱导型磷酸酪氨酸对接位点，其募集Stat 2的SH 2结构域;和iii）使用嵌合受体部分重建IFN α信号传导途径。然而，控制该途径的分子相互作用的许多细节仍然未知，包括Tyk 2激酶的哪些部分是与IFNaR 1相互作用所需的，Stat 2-Stat 1异二聚体如何从受体释放，IFNaR 1亚基的远端部分的作用以及哪些特定分子参与该途径的负调控。四个具体的目标，提出了调查这些细节中的一些：1。鉴定Tyk 2中与IFNaR 1受体亚基相互作用所需的残基。2.明确Stat 1-Stat 2异二聚体形成的机制。3.确定其他IFNaR 1相互作用的蛋白质，调节IFN α信号。4.研究CIS蛋白在Tyk 2激酶和/或IFNaR 1亚基调节中的作用。

JAK/STAT signaling cascades provide a relative simple and direct connection between ligand binding on the cell surface and gene transcription in the nucleus. These pathways mediate the response to a diverse group of polypeptide ligands which regulate cell growth, differentiation and effector function. One of the best characterized JAK/STAT signaling cascades is the pathway stimulated by interferon- alpha (IFNalpha). Extensive studies of this signal transduction cascade by a number of laboratories has provided a basic understanding of the initial molecular events regulating IFNalpha-induced gene transcription and has established a paradigm for studying other JAK-STAT pathways, as well. During the previous term of this grant, we have explored the molecular interactions between the various components in this cascade: the Tyk2 tyrosine kinase, the IFNaR1 receptor subunit, and the Stat1 and Stat2 transcription factors. In particular, we have: i) identified and characterized the Tyk2 kinase-IFNaR1 receptor complex; ii) identified and characterized the ligand-inducible Phosphotyrosine docking site on IFNaR1 which recruits the SH2 domain of Stat2; and iii) partially reconstituted the IFNalpha signaling pathway using chimeric receptors. Many details of the molecular interactions controlling this pathway, however, remain unknown, including which parts of the Tyk2 kinase are required for the interaction with IFNaR1, how the Stat2-Stat1 heterodimer is released from the receptor, the role of the distal portion of the IFNaR1 subunit and which specific molecules are involved in the negative regulation of this pathway. Four specific aims are proposed to investigate some of the these details: 1. Identify the residues in Tyk2 required for interaction with the IFNaR1 receptor subunit. 2. Define the mechanism of Stat1-Stat2 heterodimer formation. 3. Identify additional IFNaR1-interacting proteins which regulate IFNalpha signaling. 4. Investigate the role of CIS proteins in the regulation of the Tyk2 kinase and/or the IFNaR1 subunit.