ALTERNATE PATHWAYS FOR INTERFERON AND CYTOKINE SIGNALING

该项目的长期目标是了解干扰素(IFN)诱导的信号转导通路的调节，以及它们与其他细胞因子和生长因子激活的通路的相互作用。核心是Jak-Stat途径，它通过一系列特定的蛋白质-蛋白质相互作用，然后是DNA-蛋白质相互作用，其中蛋白质磷酸化起着关键作用。Jak-Stat途径与其他信号系统之间的相互作用包括胞浆磷脂酶A2(CPLA2)参与干扰素-α(而不是干扰素-γ)信号转导，依赖dsRNA的蛋白激酶PKR参与NFkappaB和IRF-1的干扰素信号转导，以及依赖PDGF的PKR和STAT3之间的物理和功能相互作用。不同的蛋白质酪氨酸磷酸酶(PTPs)也调节Jak-Stat途径。为了更好地理解这些成分在IFN和其他细胞因子对细胞信号转导中的相对作用，我们提出了以下具体目标：1.为了验证cPLA2是干扰素-α信号通路的重要成分的假设，我们将a)研究cPLA2在ISGF3激活中的作用；b)通过绘制相互作用所需的物理结构域来表征JAK1和cPLA2之间的相互作用；以及c)确定cPLA2的磷酸化在干扰素-α信号通路中的作用。2.为了验证PKR在IFNα和PDGF信号通路中发挥独特作用的假设，我们将a)剖析导致PKR的IFN-γ激活的途径以及转录因子NFkappaB和IRF-1的调节；b)研究STAT3与PKR的物理和功能相互作用，并建立PKR在STAT3介导的PDGF依赖的即刻早期基因激活中的作用。3.为了验证不同的PTP参与Jak-Stat信号负调控的假设，我们将：a)表征SHP-1缺陷细胞中IL-4/IL-13信号的调节，b)研究IL-4/IL-13信号通路各组成部分之间的物理和功能相互作用，以及c)确定负控制IL-4/IL-13信号的额外PTP-活性。了解细胞因子和生长因子对细胞信号的复杂性，将为控制细胞生长提供新的见解，并确定未来治疗恶性肿瘤的领域。

The long term objective of this project is to understand the regulation of signal transduction pathways elicited by interferons (IFNs) and their interplay with pathways activated by other cytokines and growth factors. Central to this is the Jak-Stat pathway which operates via a cascade of specific protein-protein interactions followed by DNA-protein interactions in which protein phosphorylation plays a key role. Cross-talk between the Jak-Stat pathway and other signaling systems includes the involvement of cytosolic phospholipase A2 (cPLA2) in IFN-alpha (but not IFN-gamma) signaling, the involvement of the dsRNA-dependent protein kinase PKR in IFN signaling of NFkappaB and IRF-1 and a PDGF-dependent physical and functional interaction between PKR and Stat3. Different proteins tyrosine phosphatases (PTPs) also regulate the Jak-Stat pathway. To better understand the relative contributions of these components to cell signaling by IFNs and other cytokines we propose the following specific aims: 1. To test the hypothesis that cPLA2 is an essential component of the IFN- alpha signaling pathway we will a) investigate the role of cPLA2 in ISGF3 activation; b) characterize the interaction between Jak1 and cPLA2 by mapping the physical domains required for this interaction, and c) determine the role of phosphorylation of cPLA2 in IFN-alpha signaling. 2. To test the hypothesis that PKR plays a distinctive role in IFNalpha and PDGF signaling pathways, we will a) dissect the pathway that leads to IFNgamma activation of PKR and regulation of transcription factors NFkappaB and IRF-1, b) investigate the physical and functional interactions of Stat3 with PKR and establish the role of PKR in Stat3- mediated PDGF-dependent activation of immediate early genes. 3. To test the hypothesis that different PTPs are involved in the negative regulation of Jak-Stat signaling we will: a) characterize the regulation of IL-4/IL-13 signaling in Shp-1-deficient cells, b) investigate physical and functional interactions between components of the IL-4/IL-13 signaling pathway, and c) identify additional PTP-activities that negatively control IL-4/IL-13 signaling. Understanding the complexities of cell signaling by cytokines and growth factors will provide new insights into the control of cell growth and identify areas for future therapeutic intervention in malignancies.