Nlrp3 inflammasome signaling in immune responses to Candida albicans

描述（由申请人提供）：C。白色念珠菌是一种成功的真菌寄生菌，高度适应于在宿主表面如粘膜组织上生存，在粘膜组织中它无症状地定殖于上皮表面。C.白色念珠菌还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，从粘膜皮肤念珠菌病到血流感染。即使有最佳的医疗保健，仍然有大量的死亡率和发病率与侵袭性真菌病。为了开发针对真菌病原体的新的治疗模式，详细了解参与控制病原体如C。白色是必需的。在这个建议中，我们将研究核苷酸结合域富含亮氨酸重复序列的受体（NLR）家族成员Nlrp 3在识别和响应C感染中的作用。白色念珠菌在巨噬细胞中，Nlrp 3在称为炎性体的多蛋白复合物中被激活，以响应各种各样的刺激。Nlrp 3炎性体的活化最终导致半胱氨酸蛋白酶半胱天冬酶-1的活化及其促炎细胞因子的加工和分泌。C.白色念珠菌以Nlrp 3依赖性方式激活半胱天冬酶-1，导致白细胞介素（IL）-12的释放。Nlrp 3缺陷小鼠也表现出对C.体内白色念珠菌。该提案概述了三个新的目标，将检查参与激活Nlrp 3的C的分子机制。白色念珠菌在目标1中，响应于C.将通过确定通过Syk/Card 9介导的信号传导是否是Nlrp 3炎性小体激活所需的来解决白色念珠菌的感染。在目标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C中起作用。白色念珠菌诱导的Nlrp 3炎性体活化。我们还将鉴定在酵母-菌丝转变期间表达的念珠菌特异性因子，其直接由Nlrp 3炎性小体感知。在目的3中，我们将研究Nlrp 3炎性小体如何在体内感染C.白色念珠菌，特别是如果产生IL-17的Th 17细胞的发育依赖于Nlrp 3的存在。这些研究的成功完成将有助于从分子水平上了解C.白色念珠菌激活Nlrp 3炎性体，将大大增加我们对免疫系统如何控制真菌病原体的了解。此外，对C.从这些研究中产生的白色念珠菌可能提出新的治疗方法来对抗这种病原体。 公共卫生相关性：白色念珠菌是一种真菌病原体，可引起各种机会性感染，特别是在住院患者人群中，它是导致显著发病率和死亡率的原因。了解这种病原体如何与免疫系统相互作用并逃避免疫系统将有助于我们确定治疗真菌感染的新治疗靶点，因此与公共卫生直接相关。我们的研究将集中在细胞溶质模式识别受体Nlrp 3是如何被白色念珠菌激活的，以及它如何影响宿主随后的免疫反应。此外，从拟议的研究中获得的信息也将阐明其他真菌生物的发病机制。

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. PUBLIC HEALTH RELEVANCE: Candida albicans is a fungal pathogen that causes a wide variety of opportunistic infections, particularly in hospitalized patient populations where it is responsible for significant morbidity and mortality. Understanding how this pathogen interacts with and evades the immune system will help us identify new therapeutic targets to treat fungal infections and is hence directly relevant to public health. Our studies will focus on how the cytosolic pattern recognition receptor Nlrp3 is activated by Candida albicans and how this shapes subsequent immune responses by the host. In addition the information gained from the proposed studies will also shed light on the pathogenesis of other fungal organisms.