Boonyom Rerngwit, Roytrakul Sittiruk, Thinwang Patipat
Department of Medical Technology, Faculty of Allied Health Sciences, Naresuan University, Phitsanulok, 65000, Thailand.
Proteomics Research Laboratory, National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathum Thani, 12120, Thailand.
J Genet Eng Biotechnol. 2022 Apr 5;20(1):54. doi: 10.1186/s43141-022-00336-1.
Salmonella enterica serovar Typhimurium (S. Typhimurium) causes gastroenteritis and diarrhea in humans and food-producing animals. The type III secretion system (T3SS) has been known to be a potent virulence mechanism by injecting effector proteins into the cytosol of host cells. S. Typhimurium encodes two T3SSs by Salmonella pathogenicity islands 1 and 2. Previous studies showed that T3SS shared a potent virulence mechanism and molecular structure among several gram-negative bacteria. Therefore, T3SS has been identified as an attractive target in the development of novel therapeutics for the treatment of bacterial infections. Several studies reported that small-molecule compounds are able to inhibit functions of bacterial T3SSs. A small molecule, CHClNOS, has been shown the ability to inhibit the activity of Yersinia pestis T3SS ATPase, YscN, resulting to block the secretion of effector proteins. In this study, we studied the effects and mechanism for SPI-1 T3SS inhibition of this compound in S. Typhimurium.
We demonstrated that this compound prohibited the secretion of effector proteins from Salmonella via SPI-1 T3SS at 100 μM. As the result, bacterial invasion ability into epithelial cell cultures was reduced. In contrast with previous study, the CHClNOS molecule did not inactivate the activity of SPI-1 T3SS ATPase, InvC, in Salmonella. However, we studied the global cellular effects of S. Typhimurium after being treated with this compound using a quantitative proteomic technique. These proteomic results showed that the main SPI-1 transcription regulator, InvF, and two effector proteins, SipA and SipC, were reduced in bacterial cells treated with the compound.
It may explain that action of the small-molecule compound, CHClNOS, for blocking the secretion of SPI-1 T3SS in Salmonella is through inhibition of SPI-1 regulator, InvF, expression. Further studies are necessary to identify specific mechanisms for inhibition between this small-compound and InvF SPI-1 regulator protein.
肠炎沙门氏菌鼠伤寒血清型（鼠伤寒沙门氏菌）可导致人类和产食用动物患肠胃炎和腹泻。已知III型分泌系统（T3SS）是一种强大的毒力机制，可将效应蛋白注入宿主细胞的胞质溶胶中。鼠伤寒沙门氏菌通过沙门氏菌致病岛1和2编码两种T3SS。先前的研究表明，T3SS在几种革兰氏阴性细菌中具有共同的强大毒力机制和分子结构。因此，T3SS已被确定为开发治疗细菌感染的新型疗法的一个有吸引力的靶点。几项研究报告称，小分子化合物能够抑制细菌T3SS的功能。一种小分子化合物CHClNOS已被证明能够抑制鼠疫耶尔森菌T3SS ATP酶YscN的活性，从而阻止效应蛋白的分泌。在本研究中，我们研究了该化合物对鼠伤寒沙门氏菌中SPI-1 T3SS的抑制作用及其机制。
我们证明，该化合物在100μM浓度下可通过SPI-1 T3SS阻止沙门氏菌分泌效应蛋白。结果，细菌对上皮细胞培养物的侵袭能力降低。与先前的研究不同，CHClNOS分子并未使沙门氏菌中SPI-1 T3SS ATP酶InvC的活性失活。然而，我们使用定量蛋白质组学技术研究了用该化合物处理后鼠伤寒沙门氏菌的整体细胞效应。这些蛋白质组学结果表明，在用该化合物处理的细菌细胞中，主要的SPI-1转录调节因子InvF以及两种效应蛋白SipA和SipC减少。
这可能解释了小分子化合物CHClNOS阻断沙门氏菌中SPI-1 T3SS分泌的作用是通过抑制SPI-1调节因子InvF的表达实现的。需要进一步研究以确定这种小分子化合物与InvF SPI-1调节蛋白之间抑制作用的具体机制。
