Control of interferon-activated necrosis by a virus-triggered FADD checkpoint

描述（由申请人提供）：干扰素（IFN）是一种强大的抗病毒细胞因子，可通过直接触发感染细胞的死亡来限制病毒复制。我们最近报道了一个新的途径，程序性坏死激活的干扰素的鉴定，但如何在抗病毒的先天免疫反应调节这一途径仍不清楚。在这项提案中，我们概述了一个推定的新的检查点，专门许可病毒感染的细胞通过IFN细胞坏死死亡的发现。该提案的目标是确定该检查点是如何调节的，以及它在体内急性RNA病毒感染期间的作用。我们已经发现，干扰素激活RIP 1/RIP 3激酶介导的坏死只有当衔接蛋白FADD被禁用。在未感染的细胞中，FADD隔离RIP 1以阻断坏死，但在急性RNA病毒感染时，FADD在保守丝氨酸上磷酸化（小鼠中的S191或人类中的S194），并且不再抑制RIP 1。在这些情况下，IFN激活RIP激酶并诱导坏死。这些发现代表了IFN-激活的坏死途径的第一个完整轮廓，并将FADD的磷酸化确定为推定的新的先天免疫细胞命运检查点。在本提案的第一个目标中，我们将确定FADD在病毒感染期间如何磷酸化，以及该事件如何许可IFN激活的坏死。在第二个目标中，我们将使用一种独特的小鼠模型，其中FADD不能被磷酸化，以确定在RNA病毒（包括甲型流感病毒）急性呼吸道感染期间IFN-触发的坏死性死亡的作用。这些实验的成功完成将定义IFN抗病毒反应的新分支。

DESCRIPTION (provided by applicant): The interferons (IFNs) are powerful anti-viral cytokines that can limit virus replication by directly triggering the death of infected cells. We have recently reported the identification of a new pathway of programmed necrosis activated by IFNs, but how this pathway is regulated during antiviral innate-immune responses remains unclear. In this proposal, we outline the discovery of a putative new checkpoint that specifically licenses the necrotic cell death of virus-infected cells by IFNs. The goal of this proposal is to identify how this checkpoint is regulated, and what its role is during acute RNA virus infections in vivo. We have found that IFNs activate RIP1/RIP3 kinase-mediated necrosis only when the adaptor protein FADD is disabled. In uninfected cells, FADD sequesters RIP1 to block necrosis, but upon an acute RNA virus infection, FADD becomes phosphorylated on a conserved serine (S191 in mice or S194 in humans) and can no longer inhibit RIP1. Under these circumstances, IFNs activate RIP kinases and induce necrosis. These findings represent the first complete outline of an IFN-activated necrosis pathway and identify phosphorylation of FADD as a putative new innate-immune cell-fate checkpoint. In the first Aim of this proposal, we will identify how FADD is phosphorylated during virus infections, and how this event licenses IFN-activated necrosis. In the second Aim, we will use a unique mouse model in which FADD cannot be phosphorylated to identify the role of IFN- triggered necrotic death during acute respiratory infection by RNA viruses (including influenza A). The successful completion of these experiments stands to define a new arm of the IFN antiviral response.