Nlrp3 inflammasome signaling in immune responses to Candida albicans

描述（由申请人提供）：白色念珠菌是一种成功的真菌共生菌，高度适应于在宿主表面生存，如粘膜组织，在那里它无症状地定植上皮表面。白色念珠菌也可引起严重的机会性感染，特别是在免疫功能低下的患者中，从皮肤粘膜念珠菌病到血流感染。即使有最佳的医疗护理，仍有大量的死亡率和发病率与侵袭性真菌疾病有关。为了开发针对真菌病原体的新治疗方式，需要详细了解涉及控制病原体（如白色念珠菌）的先天和适应性免疫途径。在本研究中，我们将研究富含亮氨酸重复序列受体（NLR）家族成员Nlrp3在识别和应答白色念珠菌感染中的作用。在巨噬细胞中，Nlrp3在一种称为炎性体的多蛋白复合物中被激活，以响应各种刺激。Nlrp3炎性小体的激活最终导致半胱氨酸蛋白酶caspase-1的激活及其促炎细胞因子的加工和分泌。白色念珠菌以nlrp3依赖的方式激活caspase-1，导致白细胞介素(IL)-12的释放。nlrp3缺陷小鼠体内也表现出对白色念珠菌感染的易感性增加。这一建议概述了三个新的目标，将检查参与激活Nlrp3由白色念珠菌的分子机制。在Aim 1中，将通过确定Syk/Card9介导的Nlrp3炎性体激活是否需要信号传导来解决Nlrp3炎性体激活响应白色梭菌所需的初始启动步骤。在Aim 2中，我们将利用基因靶向小鼠来确定活性氧和组织蛋白酶B是否在白色梭菌诱导的Nlrp3炎性体激活中发挥作用。我们还将确定念珠菌在酵母-菌丝转化过程中表达的特异性因子，这些因子可被Nlrp3炎性体直接感知。在Aim 3中，我们将研究Nlrp3炎性体如何在体内感染白色梭菌后形成随后的适应性免疫反应，特别是如果产生IL-17的Th17细胞的发育依赖于Nlrp3的存在。这些研究的成功完成将提供一个关于白色念珠菌如何激活Nlrp3炎性体的分子理解，并将大大增加我们对免疫系统如何控制真菌病原体的认识。此外，从这些研究中得出的关于白色念珠菌发病机制的新见解可能为对抗这种病原体提供新的治疗方法。

DESCRIPTION (provided by applicant): C. albicans is a successful fungal commensal, highly adapted to survive on host surfaces such as mucosal tissue where it asymptomatically colonizes epithelial surfaces. C. albicans can also cause severe opportunistic infections particularly in immunocompromised patients ranging from mucocutaneous candidiasis to bloodstream infections. Even with optimal medical care there is still substantial mortality and morbidity associated with invasive fungal disease. In order to develop new therapeutic modalities directed at fungal pathogens a detailed understanding of the innate and adaptive immune pathways involved in control of pathogens such as C. albicans are required. In this proposal we will examine the role of the nucleotide-binding domain leucine-rich repeat containing receptor (NLR) family member Nlrp3 in recognition and response to infection with C. albicans. In macrophages Nlrp3 is activated in a multiprotein complex called the inflammasome in response to a wide variety of stimuli. The activation of the Nlrp3 inflammasome ultimately results in the activation of the cysteine protease caspase-1 and its processing and secretion of proinflammatory cytokines. C. albicans activates caspase-1 in an Nlrp3-dependent manner leading to the release of interleukin (IL)-12. Nlrp3-deficient mice also demonstrate increased susceptibility to infection with C. albicans in vivo. This proposal outlines three novel aims that will examine the molecular mechanism involved in activation of Nlrp3 by C. albicans. In Aim 1 the initial priming step required for Nlrp3 inflammasome activation in response to C. albicans will be addressed by determining if signaling mediated through Syk/Card9 is required for Nlrp3 inflammasome activation. In Aim 2 we will utilize gene targeted mice to determine if reactive oxygen species and cathepsin B play a role in C. albicans-induced activation of the Nlrp3 inflammasome. We will also identify Candida specific factors expressed during yeast-hyphae transition that are directly sensed by the Nlrp3 inflammasome. In Aim 3 we will examine how the Nlrp3 inflammasome shapes subsequent adaptive immune responses following in vivo infection with C. albicans and in particular if the development of IL-17 producing Th17 cells is dependent on the presence of Nlrp3. Successful completion of the proposed studies will provide a molecular understanding of how C. albicans activates the Nlrp3 inflammasome, and will substantially augment our knowledge of how the immune system controls fungal pathogens. Furthermore, new insights into the pathogenesis of C. albicans that result from these studies may suggest novel therapeutic approaches to combating this pathogen.