A novel role of HSP70 proteins in antiviral immune response

非自身或非典型自身核酸对I型和III型干扰素的转录诱导是激活抗病毒天然免疫和炎症的关键步骤，也是一个需要严格控制的过程，因为过度和长期的干扰素诱导可能会导致自身免疫性疾病。在我们以前的工作中，我们已经确定了迄今为止尚未被认识的细胞HSP70蛋白家族在调节RIG-I样受体介导的干扰素诱导中的关键作用。最初，HSP70被确定为狂犬病病毒磷酸蛋白P的直接靶点，P是一种有效的干扰素拮抗剂。P与HSP70的直接结合是由特定的P肽基序介导的，不同于HSP70底物的结合。与HSP70的结合与P关闭干扰素转录因子IRF3激活的能力密切相关，这一点通过对质粒型P和工程重组病毒的诱变表明。选择的HSP70突变体的表达强烈干扰RIG-I诱导的干扰素，进一步证实了在控制干扰素诱导中的内在调节作用。在本项目中，我们的目标是明确热休克和可能的多个HSP70成员在调节干扰素反应中的新作用，并阐明像P这样的病毒蛋白如何利用HSPs来防止抗病毒宿主反应。这些研究包括对多效性HSP70功能的突变和药理学分析，以及在没有和存在工程P蛋白的情况下的细胞生物学研究。这一结果可能会为抗病毒治疗或免疫抑制设计新的策略。

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.