Regulation of Caspase-1 Signaling and Inflammation by the P2X7 ATP Receptor

P2X7受体（P2X7R）是在免疫效应细胞中表达的细胞外ATP门控离子通道，例如 作为巨噬细胞，在微生物感染的早期阶段进行关键的保护性反应， 急性组织创伤由于ATP存在于所有细胞中，因此ATP可以在100 ° C下释放到细胞外区室中。 组织损伤和微生物侵入的部位。P2X7R的刺激迅速触发了 促炎细胞因子，白细胞介素-1 β（IL-1 β）通过激活半胱天冬酶-1，一种调节 炎症和细胞死亡。因为caspase-1信号是自我放大的，而且不可逆，所以它必须是 在免疫效应细胞整合多种刺激之前， 在微生物感染或组织损伤的场所内产生。这些刺激因素包括： 病原体相关分子模式（PAMP）配体的特征性Toll样受体（TLR）， 被入侵的微生物释放出来我们认为P2X7R的激活提供了一种重要的佐剂， 对TLR和PAMP引起的caspase-1信号级联的作用。我们假设P2X7R> caspase-1> IL-1 β级联反应涉及P2X7 R信号在细胞间和细胞外的协同调节。 细胞内水平。目的1是确定P2X7 R与P2X7 R偶联的细胞内信号转导机制。 作为IL-1 β基础的caspase-1炎性体复合物的组装、活化和输出 加工和分泌。目的2是确定P2X7R调节的信号通路在活化中的作用， 非致病性与非致病性小鼠巨噬细胞体外感染过程中caspase-1/IL-1 β的表达和输出 李斯特菌和沙门氏菌的致病菌株。目的3是明确细胞外ATP依赖的 与ATP非依赖性机制相比，在P2X7 R/caspase-1/11_1 β. a级联反应的激活中， 强调细胞外NAD和胞外ADP核糖基转移酶的调节作用， 与感染和炎症部位的受损宿主细胞相互作用。这些P2X7R- 调节途径（半胱天冬酶-1的激活和IL-1 β的分泌）与多种 炎性和自身免疫性疾病，包括周期性发热综合征、克罗恩病和 类风湿性关节炎，以及致病细菌的致病性，包括沙门氏菌，志贺氏菌， 李斯特菌和炭疽

P2X7 receptors (P2X7R) are extracellular ATP-gated ion channels expressed in immune effector cells, such as macrophages, that carry out critical protective responses during the early phases of microbial infection or acute tissue trauma. Given its presence in all cells, ATP can be released into extracellular compartments at sites of tissue damage and microbial invasion. Stimulation of P2X7R rapidly triggers secretion of the proinflammatory cytokine, interleukin-1beta (IL-1beta) via activation of caspase-1, a protease that regulates inflammation and cell death. Because caspase-1 signaling is self-amplifying and poorly reversible, it must be stringently maintained in an inactive state until immune effector cells integrate multiple stimuli that are generated within the locus of microbial infection or tissue damage. These stimuli include the well- characterized Toll-like receptors (TLR) for Pathogen-Associated Molecular Pattern (PAMP) ligands that are released by invading microbes. We propose that the activation of P2X7R provides an important adjuvant action to the caspase-1 signaling cascades elicited by TLRs and PAMPs. We hypothesize that the P2X7R > caspase-1 > IL-1beta cascade involves synergistic regulation of P2X7R signaling at both the intercellular and intracellular levels. Aim 1 is to define the intracellular signal transduction mechanisms that couple P2X7R to the assembly, activation, and export of the caspase-1 inflammasome complexes which underlie IL-1beta processing and secretion. Aim 2 is to define the role of P2X7R-regulated signaling pathways in activation and export of caspase-1/ IL-1beta during in vitro infection of murine macrophages by non-pathogenic versus pathogenic strains of Listeria and Salmonella. Aim 3 is to define the roles of extracellular ATP-dependent versus ATP-independent mechanisms in the activation of the P2X7R/ caspase-1/ ll_-1bet.a cascade with emphasis on the regulatory effects of extracellular NAD and ecto-ADP-ribosyltransferases, and by interactions with damaged host cells that populate sites of infection and inflammation. These P2X7R- regulated pathways (activation of caspase-1 and secretion of IL-1beta) have been linked to multiple inflammatory and autoimmune diseases including the Periodic Fever Syndromes, Crohn's disease, and rheumatoid arthritis, as well as the pathogenicity of disease-causing bacteria including Salmonella, Shigella, Listeria, and Anthrax.