CIRI, Centre International de Recherche en Infectiologie, Université de Lyon, Inserm U1111, Université Claude Bernard Lyon 1, CNRS UMR5308, ENS de Lyon, Lyon, France.
Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, IBMC, Strasbourg, France.
Microbiol Spectr. 2023 Aug 17;11(4):e0107323. doi: 10.1128/spectrum.01073-23. Epub 2023 Jun 22.
Staphylococcus aureus gamma-hemolysin CB (HlgCB) is a core-genome-encoded pore-forming toxin that targets the C5a receptor, similar to the phage-encoded Panton-Valentine leucocidin (PVL). Absolute quantification by mass spectrometry of HlgCB in 39 community-acquired pneumonia (CAP) isolates showed considerable variations in the HlgC and HlgB yields between isolates. Moreover, although HlgC and HlgB are encoded on a single operon, their levels were dissociated in 10% of the clinical strains studied. To decipher the molecular basis for the variation in expression and protein production among strains, different regulation levels were analyzed in representative clinical isolates and reference strains. Both the HlgCB level and the HlgC/HlgB ratio were found to depend on promoter activity and mRNA processing and translation. Strikingly, only one single nucleotide polymorphism (SNP) in the 5' untranslated region (UTR) of mRNA strongly impaired translation in the USA300 strain, leading to a strong decrease in the level of HlgC but not in HlgB. Finally, we found that high levels of HlgCB synthesis led to mortality in a rabbit model of pneumonia, correlated with the implication of the role of HlgCB in severe S. aureus CAP. Taken together, this work illustrates the complexity of virulence factor expression in clinical strains and demonstrates a butterfly effect where subtle genomic variations have a major impact on phenotype and virulence. S. aureus virulence in pneumonia results in its ability to produce several virulence factors, including the leucocidin PVL. Here, we demonstrate that HlgCB, another leucocidin, which targets the same receptors as PVL, highly contributes to S. aureus virulence in -negative strains. In addition, considerable variations in HlgCB quantities are observed among clinical isolates from patients with CAP. Biomolecular analyses have revealed that a few SNPs in the promoter sequences and only one SNP in the 5' UTR of mRNA induce the differential expression of , drastically impacting mRNA translation. This work illustrates the subtlety of regulatory mechanisms in bacteria, especially the sometimes major effects on phenotypes of single nucleotide variation in noncoding regions.
金黄色葡萄球菌γ-溶血素 CB（HlgCB）是一种核心基因组编码的成孔毒素，与噬菌体编码的潘顿-瓦伦丁白细胞毒素（PVL）类似，靶向 C5a 受体。通过质谱法对 39 株社区获得性肺炎（CAP）分离株中的 HlgCB 进行绝对定量，显示分离株之间 HlgC 和 HlgB 的产量存在很大差异。此外，尽管 HlgC 和 HlgB 编码在单个操纵子上，但在研究的 10%临床菌株中，它们的水平是分离的。为了解释菌株之间表达和蛋白产生差异的分子基础，在代表性临床分离株和参考株中分析了不同的调节水平。发现 HlgCB 水平和 HlgC/HlgB 比值既取决于启动子活性，也取决于 mRNA 加工和翻译。令人惊讶的是，仅在 USA300 株 mRNA 的 5'非翻译区（UTR）中的一个单核苷酸多态性（SNP）强烈削弱了 翻译，导致 HlgC 水平大幅下降，但 HlgB 水平没有下降。最后，我们发现 HlgCB 高水平合成导致肺炎兔模型的死亡率增加，这与 HlgCB 在严重金黄色葡萄球菌 CAP 中的作用有关。总之，这项工作说明了临床菌株中毒力因子表达的复杂性，并证明了细微的基因组变异对表型和毒力有重大影响的蝴蝶效应。金黄色葡萄球菌肺炎的毒力导致其能够产生多种毒力因子，包括白细胞毒素 PVL。在这里，我们证明了另一种白细胞毒素 HlgCB 也高度参与了 -阴性菌株金黄色葡萄球菌的毒力。此外，从 CAP 患者中分离的临床分离株中观察到 HlgCB 数量存在相当大的差异。生物分子分析表明，启动子序列中的几个 SNP 和 mRNA 5'UTR 中的一个 SNP 诱导 的差异表达，极大地影响了 mRNA 的翻译。这项工作说明了细菌中调控机制的微妙性，尤其是非编码区域中单核苷酸变异对表型的有时重大影响。
