假定调控蛋白STM14_3514可降低鼠伤寒沙门菌对上皮细胞的侵袭力

Putative regulatory protein STM14_3514 decreases Salmonella Typhimurium invasion of epithelial cells

摘要:

[目的]研究鼠伤寒沙门菌致病岛1（SPI-1）内部的假定调控蛋白STM14_3514的功能及其作用机制。[方法]以鼠伤寒沙门菌模式菌株ATCC 14028为亲本株，构建了STM14_3514基因的缺失突变体及互补菌株，通过小鼠实验、细胞侵袭实验、western blot及实时荧光定量PCR （qRT-PCR）等实验技术，深入研究了STM14_3514基因对鼠伤寒沙门菌致病过程的影响。[结果]STM14_3514突变提高了细菌对小鼠的致病能力，突变体在小鼠肠道、肝和脾中的定殖能力均增强；细胞实验揭示，突变体致病力提升主要由于STM14_3514突变能显著增强细菌对上皮细胞的侵袭力（>2倍，P<0.05）。qRT-PCR及western blot分析表明，STM14_3514显著抑制SPI-1内部主要调控因子hilA及侵袭相关基因的表达。此外，STM14_3514对hilA的抑制由HilC介导。[结论]STM14_3514是鼠伤寒沙门菌SPI-1内部的负调控因子，能通过HilC抑制hilA及SPI-1其他入侵基因的表达，该基因的生物学意义可能与细菌进入细胞后对SPI-1的负调控相关。

Abstract:

[Objective] To study the function and mechanism of STM14_3514 gene that encoded in Salmonella pathogenicity island (SPI)-1 of Salmonella enterica serovar Typhimurium strain ATCC 14028. [Methods] We constructed STM14_3514 mutant strain and a complemented strain of the mutant. Through mice experiment, attachment assays, invasion assays, macrophage replication assays, western blot, and Quantitative real-time PCR analysis (qRT-PCR), we compared the virulence of the mutant strain to that of the wild-type 14028. [Results] STM14_3514 mutant shows increased virulence to mice, and the bacterial number of STM14_3514 mutant in liver, spleen, and ileum was more abundant than that of the wild-type strain. The increased virulence of STM14_3514 mutant is caused by its elevated invasion ability to epithelial cells (>2-fold and P<0.05). qRT-PCR and western blot results show that STM14_3514 reduced the expression of HilA and another SPI-1invasion locus. Moreover, the repression of HilA by STM14_3514 is mediated by HilC.[Conclusion] STM14_3514 is a negative regulator in SPI-1, which can repress HilA and SPI-1invasion locus through HilC, and possibly contribute to the repression on SPI-1 after bacterial invasion.