Intercellular cGAMP transmission induces innate immune activation and tissue inflammation in Trex1 deficiency

Intercellular transmission of the second messenger 2',3'-cGAMP, synthesized by the viral DNA sensor cGAMP synthase (cGAS), is a potent mode of bystander activation during host defense. However, whether this mechanism also contributes to cGAS-dependent autoimmunity remains unknown. Here, using a murine bone marrow transplantation strategy, we demonstrate that, in Trex1-/--associated autoimmunity, cGAMP shuttling from radioresistant to immune cells induces NF-?B activation, interferon regulatory protein 3 (IRF3) phosphorylation and subsequent interferon signaling. cGAMP travel prevented myeloid cell and lymphocyte death, promoting their accumulation in secondary lymphoid tissue. Nonetheless, it did not stimulate B cell differentiation into autoantibody-producing plasmablasts or aberrant T cell priming in the steady state. Although cGAMP-mediated bystander activation did not induce spontaneous organ disease, it did trigger interface dermatitis after UV light exposure, similar to cutaneous lupus erythematosus. These findings reveal that, in Trex1-deficiency, intercellular cGAMP transfer propagates cGAS signaling and, under conducive conditions, causes tissue inflammation. Overall design: Total RNA was isolated from single-cell suspensions of bone marrow from Cgas-/- mice and Trex1-/-;Sting1gt/gt mice (called dKO). In addition, total RNA was isolated from single-cell suspensions of spleens from dKO mice 12 weeks after they were lethally irradiated and transplanted with Cgas-/- or dKO bone marrow. 3'-mRNA Seq was performed on an Illumina HiSeq 2500.

由病毒DNA感受器环鸟苷酸-腺苷酸合成酶（cGAS, cyclic GMP-AMP synthase）催化合成的第二信使2',3'-cGAMP的细胞间传递，是宿主防御过程中介导旁侧激活的强效途径。然而，该机制是否同样参与cGAS依赖的自身免疫反应，目前仍未明确。本研究采用小鼠骨髓移植策略，证实于Trex1基因敲除（Trex1-/-）相关自身免疫模型中，cGAMP从辐射抗性细胞向免疫细胞的穿梭转运可诱导核因子κB（NF-κB）激活、干扰素调节因子3（IRF3, interferon regulatory factor 3）磷酸化，以及后续的干扰素信号通路活化。cGAMP的细胞间传递可抑制髓系细胞与淋巴细胞凋亡，促进其在次级淋巴组织中蓄积。尽管如此，在生理稳态条件下，其并未诱导B细胞分化为分泌自身抗体的浆母细胞，也未引发异常的T细胞活化启动。虽然cGAMP介导的旁侧激活不会诱导自发性器官病变，但在紫外线照射后，可触发界面性皮炎，其表现与皮肤红斑狼疮相似。上述研究结果表明，在Trex1缺陷状态下，细胞间cGAMP传递可扩增cGAS信号通路，并在适宜条件下引发组织炎症。整体实验设计：从Cgas基因敲除（Cgas-/-）小鼠及Trex1-/-;Sting1gt/gt双基因敲除小鼠（下称dKO小鼠）的骨髓单细胞悬液中提取总RNA；此外，将dKO小鼠经致死剂量辐照后，移植Cgas-/-或dKO小鼠的骨髓，并于移植后12周采集其脾脏单细胞悬液，提取总RNA；采用Illumina HiSeq 2500平台完成3'端mRNA测序（3'-mRNA Seq）。