College of Pharmacy and Research Institute of Drug Development, Chonnam National University, Gwangju, South Korea.
Clinical Vaccine R&D Center, Department of Microbiology, Combinatorial Tumor Immunotherapy MRC, Chonnam National University Medical School, Hwasun-gun, South Korea.
Front Cell Infect Microbiol. 2021 Apr 30;11:673222. doi: 10.3389/fcimb.2021.673222. eCollection 2021.
RtxA1 is a major cytotoxin of () causing fatal septicemia and necrotic wound infections. Our previous work has shown that RpoS regulates the expression and secretion of RtxA1 toxin. This study was conducted to further investigate the potential mechanisms of RpoS on RtxA1 secretion. First, TolCV1 and TolCV2 proteins, two TolC homologs, were measured at various time points by Western blotting. The expression of TolCV1 was increased time-dependently, whereas that of TolCV2 was decreased. Expression of both TolCV1 and TolCV2 was significantly downregulated in an deletion mutation. Subsequently, we explored the roles of TolCV1 and TolCV2 in pathogenesis. Western blot analysis showed that RtxA1 toxin was exported by TolCV1, not TolCV2, which was consistent with the cytotoxicity results. Furthermore, the expression of TolCV1 and TolCV2 was increased after treatment of the host signal bile salt and the growth of mutant was totally abolished in the presence of bile salt. A mutation resulted in significant reduction of induced-virulence in mice. Taken together, TolCV1 plays key roles in RtxA1 secretion, bile salt resistance, and mice lethality of , suggesting that TolCV1 could be an attractive target for the design of new medicines to treat infections.
RtxA1 是（）的一种主要细胞毒素，可导致致命性败血症和坏死性伤口感染。我们之前的工作表明，RpoS 调节 RtxA1 毒素的表达和分泌。本研究旨在进一步探讨 RpoS 对 RtxA1 分泌的潜在机制。首先，通过 Western blot 法在不同时间点测量 TolCV1 和 TolCV2 两种 TolC 同源蛋白。TolCV1 的表达随时间呈时间依赖性增加，而 TolCV2 的表达则减少。在缺失突变中，两种 TolCV1 和 TolCV2 的表达均显著下调。随后，我们探讨了 TolCV1 和 TolCV2 在发病机制中的作用。Western blot 分析表明，RtxA1 毒素是由 TolCV1 而不是 TolCV2 输出的，这与细胞毒性结果一致。此外，宿主信号胆盐处理后 TolCV1 和 TolCV2 的表达增加，而在胆盐存在下，突变体的生长完全被抑制。突变导致 诱导的小鼠毒力显著降低。总之，TolCV1 在 RtxA1 分泌、胆盐耐药和 对小鼠的致死性中起关键作用，表明 TolCV1 可能成为设计治疗 感染新药的有吸引力的靶标。
