Regulatory role for cytosolic nucleic acid sensors in bone

描述(申请人提供)：先天免疫传感器检测病毒和细菌感染的核酸以清除感染，也检测应激或濒临死亡的细胞的内源性核酸。长期以来，人们一直知道Toll样受体可以检测核酸，而细胞质中的核酸传感器直到最近才被发现。胞质DNA传感器通路的激活与自身免疫性疾病有关，在自身免疫性疾病中，来自凋亡细胞的DNA积聚。此外，细胞内的DNA内源性来源可以激活这些途径，包括随着年龄增长而积累并可以逃脱降解的氧化的、“受损的”DNA，以及来自复制人类基因组内内源性逆转录元件的DNA。尽管这些途径很重要，但除了巨噬细胞和树突状细胞外，人们对它们在细胞类型中的作用知之甚少。来自我们实验室的数据显示，骨骼中的胞质DNA传感器通路具有潜在的重要作用，可能为了解衰老和某些自身免疫性疾病中发生的骨丢失提供线索。一些胞质DNA传感器通过内质网相关蛋白、干扰素基因刺激物(STING)，包括干扰素诱导蛋白16(IFI16/p204)和环状GMP-AMP合成酶(CGAS)发出信号，导致I型干扰素和促炎细胞因子的产生。胞质DNA传感器AIM2不通过刺痛发出信号，而是协调炎症体复合体的组装，导致IL-1b的产生。我们证明胞浆DNA传感器在破骨细胞(OC)和成骨细胞(OB)谱系细胞中都有表达，而且刺痛缺陷小鼠是骨量减少的，而AIM2缺陷小鼠在长骨中积累了骨。此外，在一种由于DNaseII缺乏而导致细胞质DNA积累的关节炎小鼠模型中，STING和AIM2以不同的方式调节骨表型。我们推测，STING和AIM2通路调节OC和/或OB的分化/功能。目标1将确定STING和AIM2通路在OC分化和/或功能中的细胞内在作用。A部分将通过调节OC功能的抑制因子A20或通过产生细胞因子来确定刺痛在破骨细胞形成中的作用。B部分将确定AIM2在OC分化/功能中的炎症依赖或独立作用。我们将探索这些通路在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AIM2通路对巨噬细胞衍生的细胞因子/调节骨重建的因子表达的影响。这一建议探索了一个全新的假设，即胞浆DNA传感器及其配体调控骨重建，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.