Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada.
Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.
PLoS One. 2018 May 25;13(5):e0197491. doi: 10.1371/journal.pone.0197491. eCollection 2018.
Toll-like receptors (TLRs) recognize the conserved molecular patterns in microorganisms and trigger myeloid differentiation primary response 88 (MyD88) and/or TIR-domain-containing adapter-inducing interferon-β (TRIF) pathways that are critical for host defense against microbial infection. However, the molecular mechanisms that govern TLR signaling remain incompletely understood. Regulator of calcineurin-1 (RCAN1), a small evolutionarily conserved protein that inhibits calcineurin phosphatase activity, suppresses inflammation during Pseudomonas aeruginosa infection. Here, we define the roles for RCAN1 in P. aeruginosa lipopolysaccharide (LPS)-activated TLR4 signaling. We compared the effects of P. aeruginosa LPS challenge on bone marrow-derived macrophages from both wild-type and RCAN1-deficient mice and found that RCAN1 deficiency increased the MyD88-NF-κB-mediated cytokine production (IL-6, TNF and MIP-2), whereas TRIF-interferon-stimulated response elements (ISRE)-mediated cytokine production (IFNβ, RANTES and IP-10) was suppressed. RCAN1 deficiency caused increased IκBα phosphorylation and NF-κB activity in the MyD88-dependent pathway, but impaired ISRE activation and reduced IRF7 expression in the TRIF-dependent pathway. Complementary studies of a mouse model of P. aeruginosa LPS-induced acute pneumonia confirmed that RCAN1-deficient mice displayed greatly enhanced NF-κB activity and MyD88-NF-κB-mediated cytokine production, which correlated with enhanced pulmonary infiltration of neutrophils. By contrast, RCAN1 deficiency had little effect on the TRIF pathway in vivo. These findings demonstrate a novel regulatory role of RCAN1 in TLR signaling, which differentially regulates MyD88 and TRIF pathways.
Toll 样受体 (TLRs) 识别微生物中保守的分子模式，并触发髓样分化初级反应 88 (MyD88) 和/或 TIR 结构域包含衔接子诱导干扰素-β (TRIF) 途径，这些途径对宿主抵抗微生物感染至关重要。然而，TLR 信号转导的分子机制仍不完全清楚。钙调神经磷酸酶 1 调节因子 (RCAN1) 是一种小的进化上保守的蛋白质，可抑制钙调神经磷酸酶的活性，可抑制铜绿假单胞菌感染期间的炎症。在这里，我们定义了 RCAN1 在铜绿假单胞菌脂多糖 (LPS) 激活 TLR4 信号转导中的作用。我们比较了铜绿假单胞菌 LPS 对野生型和 RCAN1 缺陷型骨髓来源巨噬细胞的影响，发现 RCAN1 缺陷增加了 MyD88-NF-κB 介导的细胞因子产生 (IL-6、TNF 和 MIP-2)，而 TRIF-干扰素刺激反应元件 (ISRE) 介导的细胞因子产生 (IFNβ、RANTES 和 IP-10) 受到抑制。RCAN1 缺陷导致 MyD88 依赖性途径中 IκBα 磷酸化和 NF-κB 活性增加，但损害了 TRIF 依赖性途径中的 ISRE 激活和 IRF7 表达减少。铜绿假单胞菌 LPS 诱导的急性肺炎小鼠模型的补充研究证实，RCAN1 缺陷型小鼠表现出 NF-κB 活性和 MyD88-NF-κB 介导的细胞因子产生的显著增强，这与中性粒细胞在肺部的浸润增加有关。相比之下，RCAN1 缺陷对体内的 TRIF 途径影响不大。这些发现表明 RCAN1 在 TLR 信号转导中具有新的调节作用，可差异调节 MyD88 和 TRIF 途径。
