A novel role of HSP70 proteins in antiviral immune response

I型和III型干扰素（IFN）对非自身或非典型自身核酸的转录诱导是激活抗病毒先天免疫和炎症的关键步骤，这一过程需要严格控制，因为过度和慢性的IFN诱导可能导致自身免疫性疾病。在我们之前的工作中，我们已经确定了到目前为止尚未认识到的细胞HSP70蛋白家族在调节RIG-I样受体介导的IFN诱导中的关键作用。最初，HSP70被确定为狂犬病毒磷蛋白P（一种强效IFN拮抗剂）的直接靶点。P与HSP70的直接结合是由一个特定的P肽基序介导的，与HSP70底物的结合不同。与HSP70的结合与P关闭IFN转录因子IRF3的激活能力密切相关，质粒表达的P和工程重组病毒的突变表明了这一点。选定的HSP70突变体的表达强烈干扰RIG-I诱导IFN，进一步证实了其在控制IFN诱导中的内在调节作用。在目前的项目中，我们的目标是明确热休克和可能的多个HSP70成员在调节IFN反应中的新作用，并阐明像P这样的病毒蛋白如何利用HSP70来阻止抗病毒宿主反应。这些研究包括对多效性HSP70功能的突变和药理学分析，以及在缺乏和存在工程P蛋白的情况下的细胞生物学研究。研究结果可能有助于设计抗病毒治疗或免疫抑制的新策略。

Transcriptional induction of type I and III interferons (IFN) in response to non-self or atypical self-nucleic acids is a crucial step in the activation of antiviral innate immunity and inflammation, and a process that needs to be tightly controlled, as excessive and chronic IFN induction may lead to autoimmune diseases. In our previous work we have identified a so far not appreciated crucial role of the cellular HSP70 protein family in regulation of RIG-I like receptor-mediated IFN induction. Initially, HSP70 was identified as a direct target of the rabies virus phosphoprotein P, a potent IFN antagonist. Direct binding of P to HSP70 is mediated by a specific P peptide motif, and distinct from HSP70 substrate binding. Binding to HSP70 strictly correlates with the ability of P to shut down activation of the IFN transcription factor IRF3, as shown by mutagenesis of plasmid-expressed P and engineered recombinant viruses. Expression of selected HSP70 mutants strongly interferes with IFN induction by RIG-I, further confirming an intrinsic regulatory role in the control of IFN induction. In the present project we aim at specifying the novel role of heat shock and possibly multiple HSP70 members in regulation of the IFN response, and to clarify how viral proteins like P can exploit HSPs to prevent the antiviral host response. The studies involve mutational and pharmacological analyses of the pleiotropic HSP70 functions, and cell biological studies in the absence and presence of engineered P proteins. The results might allow devising novel strategies for antiviral treatment or immune suppression.