Li Zhunan, Han Jing, Jing Jiayi, Fan Ajiao, Zhang Yong, Gao Yuanpeng
Key Laboratory of Animal Biotechnology of the Ministry of Agriculture, College of Veterinary Medicine, Northwest A&F University, Yangling 712100, China.
Animals (Basel). 2024 May 31;14(11):1650. doi: 10.3390/ani14111650.
The inflammasome is a vital part of the host's innate immunity activated by cellular infection or stress. Our previous research identified the bovine SP110c isoform (bSP110c) as a novel activator of the inflammasome that promoted the secretion of proinflammatory cytokines IL-1β and IL-18 in macrophages infected with or stimulated with lipopolysaccharide (LPS). However, the exact molecular mechanism for inhibiting bSP110c-induced inflammasome activation requires further clarification. Here, the researchers identified bovine DDX3X (bDDX3X) as an NLRP3-associated protein and an inhibitor of the bSP110c-induced inflammasome in the human THP1 macrophage cell line. Immunoprecipitation showed that bDDX3X interacted with the bSP110c CARD domain via its helicase domain. The co-expression of bSP110c and bDDX3X in THP1 macrophages significantly prevented the bSP110c-induced activation of inflammasomes. In addition, both bDDX3X and bSP110c interacted with bovine NLRP3 (bNLRP3), and bDDX3X enhanced the interaction between bSP110c and bNLRP3. The expression of bDDX3X in nigericin-stimulated THP1 macrophages significantly suppressed NLRP3 inflammasome activation, ASC speck formation, and pyroptosis. These findings demonstrate that bDDX3X negatively regulates the bSP110c-mediated inflammatory response by restricting the activation of the NLRP3 inflammasome. This discovery unveils a novel regulatory mechanism involving bDDX3X and bSP110c in coordinating inflammasome activation and subsequent cell-fate decisions in LPS-treated macrophages and, in turn, constitutes a step forward toward the implementation of marker-assisted selection in breeding programs aimed at utilizing cattle's immune defenses.
炎性小体是宿主固有免疫的重要组成部分，可被细胞感染或应激激活。我们之前的研究确定牛SP110c异构体（bSP110c）是炎性小体的一种新型激活剂，可促进感染或用脂多糖（LPS）刺激的巨噬细胞中促炎细胞因子IL-1β和IL-18的分泌。然而，抑制bSP110c诱导的炎性小体激活的确切分子机制仍需进一步阐明。在此，研究人员确定牛DDX3X（bDDX3X）是一种与NLRP3相关的蛋白，也是人THP1巨噬细胞系中bSP110c诱导的炎性小体的抑制剂。免疫沉淀显示bDDX3X通过其解旋酶结构域与bSP110c的CARD结构域相互作用。bSP110c和bDDX3X在THP1巨噬细胞中的共表达显著阻止了bSP110c诱导的炎性小体激活。此外，bDDX3X和bSP110c均与牛NLRP3（bNLRP3）相互作用，并且bDDX3X增强了bSP110c与bNLRP3之间的相互作用。bDDX3X在尼日利亚菌素刺激的THP1巨噬细胞中的表达显著抑制了NLRP3炎性小体激活、ASC斑点形成和细胞焦亡。这些发现表明，bDDX3X通过限制NLRP3炎性小体的激活来负向调节bSP110c介导的炎症反应。这一发现揭示了一种涉及bDDX3X和bSP110c的新型调节机制，该机制在协调LPS处理的巨噬细胞中炎性小体激活和随后的细胞命运决定方面发挥作用，进而朝着在旨在利用牛免疫防御的育种计划中实施标记辅助选择迈出了一步。
