Regulatory role for cytosolic nucleic acid sensors in bone

描述（由申请人提供）：先天免疫传感器检测来自病毒和细菌感染的核酸以清除感染，并且还检测来自应激或垂死细胞的内源性核酸。Toll样受体早已被认为可以检测核酸，而细胞质内的核酸传感器只是最近才被发现。细胞溶质DNA传感器途径的激活与来自凋亡细胞的DNA积累的自身免疫性疾病相关。此外，细胞内DNA的内源性来源可以激活这些途径，包括随着衰老而积累并可以逃避降解的氧化的“受损”DNA，以及源自人类基因组内内源性逆转录元件复制的DNA。尽管这些途径的重要性，很少有人知道他们在细胞类型以外的巨噬细胞和树突状细胞的作用。来自我们实验室的数据表明，细胞溶质DNA传感器通路在骨中可能发挥重要作用，这可能有助于了解衰老和某些自身免疫性疾病中发生的骨丢失。几种胞质DNA传感器通过ER相关蛋白、干扰素基因刺激物（STING）（包括干扰素诱导蛋白16（IFI 16/p204）和环GMP-AMP合酶（cGAS））发出信号，导致I型干扰素和促炎细胞因子的产生。细胞溶质DNA传感器AIM 2不通过STING发出信号，而是协调炎性小体复合物的组装，导致IL-1b的产生。我们证明，细胞溶质DNA传感器在破骨细胞（OC）和成骨细胞（OB）谱系细胞中表达，STING缺陷型小鼠骨质减少，而AIM 2缺陷型小鼠在长骨中积累骨。此外，STING和AIM 2差异调节关节炎小鼠模型中的骨表型，其中细胞质DNA由于DNaseII缺乏而积累。我们假设STING和AIM 2途径调节OC和/或OB分化/功能。目的1将确定STING和AIM 2途径在OC分化和/或功能中的细胞内在作用。A部分将通过调节OC功能抑制剂A20或通过产生细胞因子来确定STING在破骨细胞生成中的作用。部分B将确定AIM 2在OC分化/功能中的炎性小体依赖性或独立性作用。我们将探讨这些途径在OBs中的作用作为一种替代方法。最后，在目标2中，我们将确定STING和AIM 2通路对调节骨重建的巨噬细胞源性细胞因子/因子表达的影响。该提案探索了一个全新的假设，即细胞溶质DNA传感器及其配体调节骨重建，并可能与衰老和自身免疫中的病理性骨重建有关。

DESCRIPTION (provided by applicant): Innate immune sensors detect nucleic acid from viral and bacterial infections to clear infection, and also detect endogenous nucleic acid from stressed or dying cells. Toll-like receptors have long been known to detect nucleic acid, while nucleic acid sensors within the cytosol have only recently been discovered. Activation of cytosolic DNA sensor pathways has been associated with autoimmune disease in which DNA from apoptotic cells accumulates. In addition, endogenous sources of DNA within cells can activate these pathways, including oxidized, "damaged" DNA that accrues with aging and can escape degradation, as well as DNA derived from replication of endogenous retroelements within the human genome. Despite the importance of these pathways, little is known about their role in cell types other than macrophages and dendritic cells. Data from our laboratory demonstrate a potentially important role for cytosolic DNA sensor pathways in bone that may provide insight into the bone loss occurring in aging and in certain autoimmune diseases. Several cytosolic DNA sensors signal through an ER-associated protein, stimulator of interferon genes (STING), including interferon-inducible protein 16 (IFI16/p204) and cyclic GMP-AMP synthase (cGAS), resulting in the production of type I interferons and proinflammatory cytokines. The cytosolic DNA sensor AIM2 does not signal through STING, but instead coordinates the assembly of an inflammasome complex, resulting in IL-1b production. We demonstrate that cytosolic DNA sensors are expressed in both osteoclast (OC) and osteoblast (OB)-lineage cells and that STING deficient mice are osteopenic, whereas AIM2 deficient mice accrue bone in long bones. Furthermore, STING and AIM2 differentially modulate the bone phenotype in a mouse model of arthritis in which cytoplasmic DNA accumulates due to deficiency in DNaseII. We hypothesize that the STING and AIM2 pathways regulate OC and/or OB differentiation/function. Aim 1 will determine the cell-intrinsic role of the STING and AIM2 pathways in OC differentiation and/or function. Part A will determine the role of STING in osteoclastogenesis through regulation of the inhibitor of OC function, A20, or through production of cytokines. Part B will determine inflammasome-dependent or independent roles of AIM2 in OC differentiation/function. We will explore the role of these pathways in OBs as an alternative approach. Finally, in Aim 2 we will determine the impact of the STING and AIM2 pathways on expression of macrophage-derived cytokines/factors that regulate bone remodeling. This proposal explores the entirely novel hypothesis that cytosolic DNA sensors and their ligands regulate bone remodeling and may be relevant to pathologic bone remodeling in aging and autoimmunity.