Role of caspase-8 in innate immunity to infection

项目总结 尽管炎症反应在控制感染中起着关键作用，但失调的炎症反应 与炎症和免疫介导性疾病有关。IL-1b是一种在宿主体内发挥作用的细胞因子 防御作为炎症的始发者，以及髓系细胞合成和释放IL-1b的途径 都被描述过。在经典的激活途径中，通过Toll样受体(TLRs)的信号触发核因子-kB 激活和IL-1b转录，前-IL-1b被蛋白水解酶切割成成熟的、具有生物活性的IL-1b Caspase-1在炎症小体中发挥作用。这一途径在小鼠巨噬细胞中表现得最好。 然而，有趣的是，人类细胞对炎症体的调节与小鼠细胞不同，而且 这些炎症途径的功能差异的分子基础相对较少。 我研究的长期目标是确定人类先天免疫的分子机制 感染细胞内原生动物弓形虫。尽管弓形虫感染估计 全世界三分之一的人类会导致免疫功能受损的人患上致命疾病，相对较少的人是 已知人类对这种寄生虫的先天识别，因为在老鼠身上识别弓形虫的TLRs (TLR11/TLR12)在人类细胞中不起作用。我们最近报道了人类外周感染 弓形虫感染的血单核细胞通过Syk-CARD9-NF-kB信号和NLRP3释放IL-1b 炎性小体激活。在使用基因敲除细胞和药物抑制剂的初步研究中， 我们发现caspase-8缺乏导致弓形虫感染者IL-1b释放减少。 单核细胞。我们推测caspase-8参与了炎症小体下游IL-1b的释放。 弓形虫感染人单核细胞过程中的激活。Caspase-8对炎症和单核细胞至关重要- 介导小鼠对弓形虫的宿主防御。然而，目前仍不清楚caspase-8在 弓形虫感染人单核细胞的炎症途径。这项建议的目的是 确定caspase-8在调节弓形虫感染人单核细胞释放IL-1b中的作用。 这项研究意义重大，因为人类免疫细胞中的炎症途径相对较少。 明确并理解这些过程可能有助于开发治疗方法来调节或 抑制炎症。在目标1中，我们将确定caspase-8在感染的人释放IL-1b中的作用。 单核细胞。在目标2中，我们将定义caspase-8活性的功能要求，包括其处理 以及在弓形虫感染期间与细胞伙伴的联系。这项提议试图破译分子 弓形虫感染人单核细胞过程中炎症信号的决定因素 确定响应感染全球健康的人类病原体而激活的先天免疫途径 重要性。

PROJECT SUMMARY Although inflammatory responses play a key role in controlling infection, dysregulated inflammation is associated with inflammatory and immune-mediated diseases. IL-1b is a cytokine that functions in host defense as an initiator of inflammation, and the pathways of IL-1b synthesis and release by myeloid cells have been described. In the classical pathway of activation, signals through Toll-like receptors (TLRs) trigger NF-kB activation and IL-1b transcription, and pro-IL-1b is proteolytically cleaved to mature, bioactive IL-1b by caspase-1 functioning in the inflammasome. This pathway is best characterized in mouse macrophages. Interestingly, however, human cells regulate the inflammasome differently than mouse cells, and the molecular basis for the functional differences in these inflammatory pathways are relatively poorly understood. The long-term goal of my research is to define molecular mechanisms of human innate immunity during infection with the intracellular protozoan parasite Toxoplasma gondii. Although T. gondii infects an estimated one-third of humans worldwide and causes fatal disease in immune-compromised individuals, relatively little is known about human innate recognition of the parasite, since the TLRs that recognize T. gondii in mice (TLR11/TLR12) are not functional in human cells. We recently reported that infection of human peripheral blood monocytes with T. gondii results in IL-1b release via Syk-CARD9-NF-kB signaling and NLRP3 inflammasome activation. In preliminary studies using genetic knockout cells and pharmacological inhibitors, we found that caspase-8 deficiency resulted in reduced IL-1b release from T. gondii-infected human monocytes. We hypothesize that caspase-8 is involved in IL-1b release downstream of inflammasome activation during T. gondii infection of human monocytes. Caspase-8 is critical for inflammation and monocyte- mediated host defense against T. gondii in mice. However, it remains unknown how caspase-8 functions in inflammatory pathways during T. gondii infection of human monocytes. The objective of this proposal is to determine the role of caspase-8 in the regulation of IL-1b release from T. gondii-infected human monocytes. This research is significant because pathways of inflammation in human immune cells are relatively poorly defined, and understanding these processes may contribute to efforts to develop therapeutics to modulate or dampen inflammation. In Aim 1, we will determine the role of caspase-8 in IL-1b release from infected monocytes. In Aim 2, we will define the functional requirements of caspase-8 activity, including its processing and association with cellular partners, during T. gondii infection. This proposal seeks to decipher the molecular determinants of inflammatory signaling during T. gondii infection of human monocytes and will contribute to defining innate immune pathways activated in response to infection with a human pathogen of global health importance.