转录因子PLZF在干扰素IFN调控抗病毒感染中的作用

Interferons (IFNs) modulate distinct aspects of both innate and adaptive immunity. They affect the activities of macrophages, natural killer cells, dendritic cells and T cells by enhancing IFN-stimulated gene (ISG) expression profiles via the Janus kinase-signal transducers and activator of transcription (JAK-STAT) pathway. IFNs have been used therapeutically against a variety of diseases. The factors determining the outcome of IFN treatment, however, are not understood and IFN therapy has had variable success. Although the essential JAK-STAT signal transduction pathway is well characterised, recent studies have revealed greater complexity in patterns of gene induction than initially envisaged. The response via the canonical JAK-STAT pathway alone is not sufficient to explain all the biological effects of type I IFNs. Our recent studies have identified a novel IFN-mediated signal that leads to activation of the promyelocytic leukemia zinc finger protein (PLZF) transcription factor that has fundamental consequences for the innate immune response (Xu et al Immunity 2009, AL&Xu et al Immunity 2012). The molecular mechanisms of PLZF action in the regulation of the innate immune response remain to be determined. We have shown that an IFN-mediated signal results in the phosphorylation of PLZF and its engagement in a transcription factor complex that includes the canonical STAT proteins. Our preliminary data suggest that PLZF has a synergistic effect on IFN regulatory factor (IRF)/STAT transcription factors, which may support crosstalk between these molecular pathways to enhance IFN signalling. In addition, we have identified DNA-binding motifs for PLZF in the promoters of two microRNAs (miRNAs), miR-155 and miR-146, previously linked to innate immunity. Thus a potential role for PLZF in the transcriptional regulation of these key miRNAs reveals a new level of complexity in our understanding of innate immune gene regulation. In support of this, preliminary data show that PLZF negatively regulates miR-155 and miR-146 in the context of innate immune receptor recruitment. Moreover, we have found that PLZF is elevated in mouse embryonic fibroblasts (MEFs) from miRNA-deficient mice (Dicer1 conditional knockout) treated with IFN. This suggests that PLZF expression itself is under negative regulation by miRNAs and reveals a level of complex regulation heretofore unrecognized. In this project we will examine the interplay between PLZF and miRNAs, focusing on miR-146 and miR-155 and utilising miRNA-deficient mice to provide a detailed understanding of coordinated ISG regulation by miRNA and PLZF. The outcomes of this project will provide new insights into the regulatory circuits of antiviral immunity(Fig1).

干扰素（IFNs）在免疫中发挥着重要作用。IFNs可通过JAK-STAT通路加强IFN刺激基因ISG表达模式影响免疫细胞的活性。IFNs已被应用于临床多种疾病的治疗。然而影响IFN治疗效果的因素尚未明确。单独的JAK-STAT通路反应不足以解释所有的I型干扰素的生物学效应。我们该项目的研究发现了早幼粒细胞白血病锌指蛋白（PLZF）转录因子调控的一条新的IFN介导信号通路，PLZF具有先天免疫反应的基本作用(Xu et al Immunity 2009,2012)。PLZF调控免疫的分子机制尚不明,我们的预实验结果表明PLZF对干扰素调节因子IRF/STAT具有协同作用,另外PLZF负向调控在免疫中发挥重要作用的miR-155和miR-146,IFN处理的miRNA缺陷小鼠的细胞高表达PLZF。本课题将重点检测miRNA和PLZF协调调控ISG，这将为抗病毒免疫的调控网络提供新的认识(图1)

Toll样受体(TLRs)既是机体天然免疫信号受体,同时也是炎症信号受体,TLRs被激活后可诱导干扰素（IFN）和NFkB介导的调控信号通路在抵抗病原感染和各种刺激时发挥着重要作用。如果调控紊乱，将导致多种疾病的发生，因此这些信号调控网络是多种疾病发生的根本原因。我们课题组以往的研究揭示了这些应答如何精确调控防止感染和炎症性疾病的发生。我们的目的是选择性调控基因转录的表达以减少相关的病理损害，同时又能保持机体对感染的反应。我们以往的结果证实急性早幼粒细胞白血病锌指蛋白（promyelocytic leukemia zinc finger protein, PLZF）转录因子在机体抗病毒反应中发挥重要作用 (Immunity 2009). 最近，我们又发现PLZF在表观水平上调控与限制NFkB 的活性（PNAS & Nat Commun 2015）。成为综述亮点在 Nature Reviews Immunology (Xuetao Cao，2016). 完全抑制NFkB的活性可导致无法控制的炎症发生等严重的机体损害，因此对NFkB恰当的调控才有利于多种疾病的治疗，我们已证实PLZF只影响部分NFkB依赖的促炎转录因子。. 炎症信号的第二条信号（炎症小体）相对于第一条信号（TLRs）在先天性免疫中扮演关键角色， 炎症小体的异常调节与大量自身免疫性疾病等相关。然而，它的激活以及调节机制仍未知,类风湿性关节炎是一种慢性的自身免疫性疾病，在风湿性疾病的软骨破坏中，白介素-1β（IL-1β）是一个关键因素，但是在一些合适的敲除小鼠模型中IL-1β的调节受到限制。这里我们建立了用K/BXN小鼠血浆诱导的小鼠关节炎模型。它的调节主要依赖于ASC（炎症小体，可以促进IL-1β分泌）炎症小体和IL-1 β受体信号。在巨噬细胞中，当我们敲除PLZF后可以减低炎症小体适配子ASC的蛋白表达水平，然而IL-1 β前体（pro-IL-1β）并没有改变。因此，巨噬细胞中PLZF敲除后，当刺激NLRP3后，可以显著降低ASC炎症小体介导的caspase-1激活，细胞凋亡以及IL-1 β的分泌。重要的是在PLZF敲除小鼠中发现，降低ASC炎症小体的活性可以限制类风湿性关节炎的病理改变。 这些结果揭示了PLZF作为ASC炎症小体的重要调节子，可以促进类风湿性关节炎相关的炎症小体疾病以及软骨破坏