Dissecting the mechanism of RIPK1 kinase-dependent cell death in control of Yersinia infection

项目摘要 针对细菌感染的免疫防御需要激活上调表达的保守信号通路 产生炎性介质以清除感染。许多病原体，包括致病性耶尔森氏菌 抑制这些信号通路，以逃避宿主的免疫防御。耶尔西尼亚病毒注入了一种毒力因子， YopJ，阻断NF-ΚB和MAPK信号转导。免疫防御是如何介导对抗病原体的 阻断免疫信号通路仍然知之甚少。核因子-κB对暴露于巨噬细胞的阻断作用 细菌PAMPs导致的细胞死亡以细胞凋亡为特征，但这种死亡具有促炎作用 后果。值得注意的是，假结核杆菌或鼠疫杆菌的细胞毒性增加会导致减少 细菌毒力，表明诱导细胞死亡是对耶尔森氏菌的一种宿主免疫 保护机制。我们的中心假说是耶尔森氏菌阻断引起的细胞死亡 核因子-κB和丝裂原活化蛋白激酶释放促炎信号，提醒未感染的邻近细胞注意 感染。然而，这种反应的细胞和分子基础仍不清楚。我们最近出版的 初步数据表明，RIPK1激酶活性是耶尔森氏菌诱导细胞死亡所必需的。 此外，RIPK1激酶活性有助于控制耶尔森氏菌感染和炎性细胞因子 活体生产。然而，RIPK1激酶活性和细胞死亡是如何与炎症联系在一起的 对细菌感染的反应和宿主防御尚不清楚。这是一个重要的问题，因为 通路可能对许多病原体做出反应，这些病原体阻断了关键的先天性免疫信号通路，并且在 导致RIPK1诱导细胞死亡的病理刺激的背景。我们提出了两个具体目标来解决 我们知识中的这一重要鸿沟。首先，我们将定义需要RIPK1激酶的细胞群体 活性，并确定RIPK1是以细胞内的方式还是以细胞外的方式发挥功能来介导抗菌 免疫防御。其次，我们将确定RIPK1对下游病原体特异性的贡献 并将剖析RIPK1是否具有控制细菌传播或复制的功能。

Project Summary Immune defense against bacterial infection requires activation of conserved signaling pathways that upregulate production of inflammatory mediators to clear infection. Many pathogens, including the pathogenic Yersinia inhibit these signaling pathways in order to evade host immune defenses. Yersinia injects a virulence factor, YopJ, which blocks NF-ΚB and MAPK signaling. How immune defense is mediated against pathogens that block immune signaling pathways remains poorly understood. NF-κB blockade in macrophages exposed to bacterial PAMPs leads to cell death with characteristics of apoptosis, yet this death has pro-inflammatory consequences. Notably, increasing cytotoxicity of Y. pseudotuberculosis or Y. pestis results in decreased bacterial virulence, suggesting that induction of cell death in response to Yersinia serves as a host immune protective mechanism. Our central hypothesis is that cell death triggered in response to Yersinia blockade of NF-κB and MAPK releases pro-inflammatory signals that alert uninfected neighboring cells to the presence of infection. However, the cellular and molecular basis for this response remains unclear. Our recently published and preliminary data demonstrate that RIPK1 kinase activity is required for Yersinia-induced cell death. Moreover, RIPK1 kinase activity contributes to control of Yersinia infection and to inflammatory cytokine production in vivo. Nevertheless, how RIPK1 kinase activity and cell death are coupled to inflammatory responses and host defense against bacterial infection is not known. This is an important problem as this pathway likely responds to many pathogens that block critical innate immune signaling pathways and in the context of pathological stimuli that lead to RIPK1-induced cell death. We propose two Specific Aims to address this important gap in our knowledge. First we will define the cellular population that requires RIPK1 kinase activity, and determine whether RIPK1 functions in a cell-intrinsic or extrinsic manner to mediate anti-bacterial immune defense. Second, we will will determine the contribution of RIPK1 to downstream pathogen-specific immune responses and will dissect whether RIPK1 functions to control bacterial dissemination or replication.