Tandhavanant Sarunporn, Terashima Hiroyuki, Hiyoshi Hirotaka, Anggramukti Dhira Saraswati, Precha Nopadol, Iida Tetsuya, Matsuda Shigeaki, Chantratita Narisara, Kodama Toshio
Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
mSystems. 2025 Jul 22;10(7):e0025125. doi: 10.1128/msystems.00251-25. Epub 2025 Jun 17.
Many pathogenic bacteria regulate gene expression in response to the surrounding environment to establish infection. One such mechanism is the regulation of gene expression in response to contact with host cells. Here, we show that , a causative agent of foodborne gastroenteritis, has a host-cell contact-dependent regulatory mechanism for virulence gene expression. Type III secretion system 2 (T3SS2), an essential virulence determinant for acute gastroenteritis encoded by pathogenicity island (Vp-PAI), recognizes host-cell contact by sensing high intracellular K levels and switching its secretory substrates. The switching of secretory substrates is regulated by proteins called gatekeepers. Mutants deficient in the gatekeeper genes lose the ability to switch secretory substrates and lock their secretory state into a host-cell contact-dependent manner. Transcriptomic analysis of these mutants revealed the upregulation of Vp-PAI genes, which was dependent on T3SS2 secretory activity, suggesting the presence of a negative regulator secreted by T3SS2. Comparative proteomic analyses identified a previously unrecognized T3SS2 secretory substrate, VPA1369 (VtrN), that negatively regulates Vp-PAI gene transcription. Secretion of VtrN was promoted under conditions that mimic host-cell contact. gene deletion specifically upregulated Vp-PAI gene expression, independent of T3SS2 secretory activity, indicating its role as a repressor. VtrN interacts with VtrB, a key transcription factor for Vp-PAI genes, suppressing its transcriptional activity. This mechanism illustrates how enhances virulence gene expression upon host-cell contact through the T3SS2 recognition system, highlighting an adaptive strategy for establishing infection.IMPORTANCEThe type III secretion system (T3SS) is a crucial virulence factor tightly regulated for optimal host manipulation and virulence. This study revealed that the expression of T3SS2, a key virulence factor in that causes acute gastroenteritis, is strictly regulated by host-cell contact. VtrN, a negative regulator exported from the bacterium through T3SS2, plays a key role in this host-cell contact-dependent gene transcriptional process. VtrN binds directly to the master regulator of Vp-PAI, the region encoding T3SS2, and represses its transcriptional activity. Upon host-cell contact, VtrN export is promoted, leading to the derepression of Vp-PAI gene expression. Thus, can effectively upregulate the expression of virulence factors when interacting with the host cells. Understanding these regulatory mechanisms could lead to innovative infection control strategies, opening new avenues for research and discovery.
许多致病细菌会根据周围环境调节基因表达以建立感染。其中一种机制是响应与宿主细胞的接触来调节基因表达。在此，我们表明，食源性肠胃炎的病原体，具有一种针对毒力基因表达的宿主细胞接触依赖性调节机制。III型分泌系统2（T3SS2）是由致病岛（Vp-PAI）编码的急性肠胃炎的必需毒力决定因素，它通过感知高细胞内钾水平并切换其分泌底物来识别宿主细胞接触。分泌底物的切换由称为守门人的蛋白质调节。缺乏守门人基因的突变体失去了切换分泌底物的能力，并以宿主细胞接触依赖性方式锁定其分泌状态。对这些突变体的转录组分析揭示了Vp-PAI基因的上调，这取决于T3SS2的分泌活性，表明存在一种由T3SS2分泌的负调节因子。比较蛋白质组学分析确定了一种以前未被识别的T3SS2分泌底物VPA1369（VtrN），它对Vp-PAI基因转录起负调节作用。在模拟宿主细胞接触的条件下，VtrN的分泌得到促进。基因缺失特异性地上调了Vp-PAI基因表达，与T3SS2分泌活性无关，表明其作为阻遏物的作用。VtrN与Vp-PAI基因的关键转录因子VtrB相互作用，抑制其转录活性。这种机制说明了如何通过T3SS2识别系统在宿主细胞接触时增强毒力基因表达，突出了一种建立感染的适应性策略。重要性III型分泌系统（T3SS）是一种关键的毒力因子，受到严格调控以实现对宿主的最佳操控和毒力。这项研究表明，导致急性肠胃炎的关键毒力因子T3SS2的表达受到宿主细胞接触的严格调控。VtrN是一种通过T3SS2从细菌中输出的负调节因子，在这个宿主细胞接触依赖性基因转录过程中起关键作用。VtrN直接与编码T3SS2的区域Vp-PAI的主调节因子结合，并抑制其转录活性。在宿主细胞接触时，VtrN的输出得到促进，导致Vp-PAI基因表达的去抑制。因此，在与宿主细胞相互作用时可以有效地上调毒力因子的表达。了解这些调节机制可能会带来创新的感染控制策略，为研究和发现开辟新的途径。
