BCAP regulation of TLR7/9 signaling in Lupus

项目摘要 系统性红斑狼疮（SLE）是一种复杂的自身免疫性疾病，其特征在于存在 自身抗体的循环，以核酸和蛋白质与他们联系。信令通过 核酸感应TLR，TLR 7和TLR 9，在SLE发病机制中至关重要，TLR信号转导失调 可以促进人类和小鼠模型中的狼疮。浆细胞样树突状细胞（pDC）和B细胞均 表达这些核酸感应TLR并且在SLE发病机制中是重要的。自身反应性B细胞产生 SLE中的致病性自身抗体和B细胞抗体的产生通过TLR 7和TLR 9信号传导促进。 pDC利用TLR 7和TLR 9应答免疫复合物中的核酸，导致分泌大量的 大量的I型IFN细胞因子，其对免疫应答具有多效性作用，包括增强 树突状细胞（DC）成熟、浆细胞形成和T细胞应答，所有这些都可以促进饲料 免疫激活的前向循环因此，了解TLR 7和TLR 9 在这两种关键细胞类型中调节信号传导对于理解SLE的发病机制是重要的 以及确定这种疾病的治疗靶点。我们已经确定了信号适配器B细胞适配器， PI 3-激酶（BCAP）作为多种免疫谱系中TLR信号传导的关键调节剂。首先，我们发现， 巨噬细胞BCAP通过激活PI 3-激酶抑制TLR诱导的炎性细胞因子产生。我们 最近表明，BCAP促进pDC IFNα分泌，但不促进IL-6分泌。我们也开始研究 BCAP调节B细胞TLR 7/9应答，这是一个研究不足的领域。我们的初步数据显示，BCAP是一种 所有B细胞亚群中B细胞TLR 7/9应答的关键调节因子， 脾边缘区B细胞增殖和IgG分泌。此外，我们还发现BCAP- TLR7.1缺陷保护小鼠狼疮模型免于疾病。总之，我们的研究结果表明， BCAP在pDC和B细胞中的内体TLR信号传导中的作用，两者在SLE发病机制中都很重要。鉴于 TLR 7和TLR 9信号传导在SLE中的B细胞和pDC中的重要性，本申请的前提是 BCAP对pDC和B细胞TLR 7/9信号传导的调节在狼疮样疾病的发展中至关重要。 具体来说，我们将1）确定BCAP调节TLR 7/9诱导的IFNα产生的机制， pDCs，2）确定BCAP调节B细胞TLR 7/9应答的机制，和3）确定BCAP的免疫应答。 使用两种小鼠模型，pDC和B细胞中BCAP对狼疮样疾病的相对贡献。

PROJECT SUMMARY Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by the presence of circulating autoantibodies to nucleic acids and to proteins with which they associate. Signaling through the nucleic acid sensing TLRs, TLR7 and TLR9, is critical in SLE pathogenesis, and dysregulated TLR signaling can promote lupus in humans and in mouse models. Plasmacytoid dendritic cells (pDC) and B cells both express these nucleic acid sensing TLR and are important in SLE pathogenesis. Autoreactive B cells produce pathogenic autoantibodies in SLE, and B cell antibody production is promoted by TLR7 and TLR9 signaling. pDC use TLR7 and TLR9 to respond to nucleic acids in immune complexes resulting in the secretion of large quantities of type I IFN cytokines, which have pleiotropic effects on the immune response, including enhancing dendritic cell (DC) maturation, plasma cell formation, and T cell responses, all of which can promote a feed forward loop of immune activation. Therefore, understanding the mechanisms by which TLR7 and TLR9 signaling are regulated in these two critical cell types is important for understanding the pathogenesis of SLE and in defining therapeutic targets for this disease. We have identified the signaling adapter B cell adapter for PI3-kinase (BCAP) as a key modulator of TLR signaling in multiple immune lineages. First, we found that in macrophages BCAP inhibits TLR-induced inflammatory cytokine production via activation of PI3-kinase. We recently showed that BCAP promotes pDC IFNα, but not IL-6, secretion. We have also begun to examine how BCAP regulates B cell TLR7/9 responses, an understudied area. Our preliminary data show that BCAP is a key regulator of B cell TLR7/9 responses in all B cell subsets, with a particularly striking decrease in proliferation and IgG secretion from splenic marginal zone B cells. Additionally, we have found that BCAP- deficiency protects the TLR7.1 mouse lupus model from disease. Together, our findings show an important role of BCAP in endosomal TLR signaling in pDC and B cells, both important in SLE pathogenesis. Given the importance of TLR7 and TLR9 signaling in both B cells and pDC in SLE, the premise of this application is that BCAP regulation of pDC and B cell TLR7/9 signaling is critical in the development of lupus-like disease. Specifically, we will 1) determine the mechanism by which BCAP regulates TLR7/9-induced IFNα production in pDCs, 2) determine the mechanism by which BCAP regulates B cell TLR7/9 responses, and 3) determine the relative contribution of BCAP in pDCs and B cells to lupus-like disease using two mouse models.