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目的:确定钩端螺旋体LA_RS06960基因产物蛋白具有磷酸二酯酶(PDE)活性，确定该酶降解的底物细菌二核苷酸可激活巨噬细胞固有免疫因子。方法:PCR扩增钩端螺旋体56601株LA_RS06960基因并构建原核表达系统。通过Ni-NTA亲和层析法提纯表达的目的重组蛋白rPDE。高效液相色谱法(HPLC)检测rPDE降解细菌二核苷酸c-di-AMP或5′-pApA底物为AMP的活性。荧光定量RT-PCR法检测钩端螺旋体感染巨噬细胞过程中钩体LA_RS06960基因和细胞固有免疫相关因子基因mRNA水平变化。采用荧光定量RT-PCR法和ELISA法检测细菌二核苷酸影响细胞固有免疫相关因子表达及分泌水平变化。结果:成功构建钩端螺旋体LA_RS06960基因原核表达系统，纯化的rPDE具有体外降解5′-pApA和c-di-AMP为AMP的功能。钩端螺旋体感染巨噬细胞过程中，钩体LA_RS06960基因表达水平显著下降，巨噬细胞IFN-β、TNF-α、IL-6以及IL-1β编码基因表达水平均显著升高。LA_RS06960编码的PDE酶降解底物细菌二核苷酸可诱导IFN-β和IL-6基因mRNA表达水平或蛋白分泌水平的升高。结论:LA_RS06960基因产物PDE具有PDE活性，其水解底物细菌二核苷酸激活巨噬细胞固有免疫应答。

Objective:To identify the phosphodiesterase (PDE) activity of the gene product encoded by LA_RS06960 of Leptospira interrogans ( L. interrogans), and analyze whether dinucleotides that can be degraded by PDE can activate macrophages to express innate immune factors. Methods:The LA_RS06960 gene in L. interrogans strain 56601 was amplified by PCR, and the prokaryotic expression system was constructed for the protein expression. The expressed rPDE was purified by Ni-NTA affinity chromatography. High performance liquid chromatography (HPLC) was used to measure the degration of c-di-AMP or 5′-pApA to AMP by rPDE. Real-time fluorescent quantitative RT-PCR (qRT-PCR) was used to detect the changes in the expression of target genes in Leptospira or THP-1 cells associated with innate immune factors during infection. qRT-PCR and ELISA were used to detect the changes in the expression and secretion level of the innate immune factors in macrophages treated with bacterial dinucleotide. Results:The prokaryotic expression system for LA_RS06960 gene of L. interrogans was constracted successfully, and the purified rPDE could degrate 5′-pApA and c-di-AMP into AMP in vitro. The mRNA level of leptospiral LA_RS06960 gene was significantly down-regulated, while IFN-β, TNF-α, IL-6 and IL-1β encoding genes of macrophages were significantly up-regulated during infection. The mRNA level or the secretion level of IFN-β and IL-6 of macrophages were increased after treated with the bacterial dinucleotide substrate of PDE. Conclusions:PDE encoded by LA_RS06960 gene has phosphodiesterase activity, and the bacterial dinucleotide substrate of the PDE could activate the innate immune response of macrophages.