Functional characterization of CARD9 genetic variants in fungal immunity

摘要 真菌是皮肤和粘膜表面无处不在的定殖者。虽然许多人表现出轻微的真菌生长，但数以百万计的人经历了危及生命的系统性感染。许多基因的多态与个体对真菌病原体产生炎症反应的能力有关。在这些基因中的许多中，已经观察到罕见的高外显性等位基因，它们强烈破坏基因功能，导致初级免疫缺陷和传染病易感性的增加。此外，据报道，在这些基因中有常见的遗传变异，它们通过改变基因产物的活性或表达来增加疾病的风险，程度很小，但很明显。这些基因为理解如何调整对病原体的免疫反应以实现适当水平的免疫反应提供了一个独特的机会。与CARD9的不同遗传变异相关的各种表型很好地说明了这一假设。CARD9是一种信号蛋白，在许多C型凝集素受体(CLR)下游发挥作用，CLR识别真菌和其他病原体上的碳水化合物部分。了解这些与人类疾病相关的CARD9突变是如何影响CARD9功能的，将促进我们对真菌免疫的理解。在这项建议的目标1中，我们研究了CARD9泛素化在树突状细胞检测真菌中的作用。在目标2中，我们将确定控制CARD9磷酸化的分子机制及其对真菌检测的影响。在目标3中，我们比较了CARD9基因变异如何影响念珠菌感染和结肠炎的发展。总之，这些目标将破译CARD9调节的机制基础，并表征CARD9基因变异，以确定在真菌防御和炎症中具有重要作用的新的分子机制。

ABSTRACT Fungi are ubiquitous colonizers of skin and mucosal surfaces. While many individuals exhibit minor fungal outgrowth, millions of others experience systemic infections with life-threatening consequences. Polymorphisms in numerous genes have been associated with the ability of an individual to generate an inflammatory response to fungal pathogens. In many of these genes, rare high-penetrance alleles have been observed that strongly disrupt gene function, resulting in primary immunodeficiencies and an increase in infectious disease susceptibility. Additionally, common genetic variants have been reported in these genes that increase the risk of disease by modifying the activity or expression of the gene product to a small but significant degree. These genes offer a unique opportunity to understand how immune responses to pathogens are tuned to achieve an appropriate level of immune response. This hypothesis is well illustrated by the various phenotypes associated with different genetic variants of CARD9. CARD9 is a signaling protein that functions downstream of many C type lectin receptors (CLRs), which recognize carbohydrate moieties on fungi and other pathogens. Understanding how these human disease-related CARD9 mutations affect CARD9 functions will advance our understanding of fungal immunity. In Aim 1 of this proposal, we examine the role of Card9 ubiquitination on fungal detection by dendritic cells. In Aim 2, we will identify the molecular mechanisms controlling Card9 phosphorylation and their consequences for fungal detection. In Aim 3, we compare how Card9 genetic variants affect Candida infection and the development of colitis. Together, these aims will decipher the mechanistic basis of CARD9 regulation and characterize CARD9 genetic variants to identify novel molecular mechanisms with important roles in fungal defense and inflammation.