Repression of the RcsC-YojN-RcsB phosphorelay by the IgaA protein is a requisite for Salmonella virulence
Repression of the RcsC-YojN-RcsB phosphorelay by the IgaA protein is a requisite for Salmonella virulence
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DOI：
10.1111/j.1365-2958.2004.04213.x
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发表时间：
2004-09-01
影响因子：
3.6
通讯作者：
García-del Portillo, F
中科院分区：
文献类型：
--
作者：
Domínguez-Bernal, G;Pucciarelli, MG;García-del Portillo, F
细菌的致病机制依赖于激活毒力基因的调节因子。此外，它们中的一些还充当特定基因的阻遏物。胞内生长衰减因子A（IgaA）是一种肠道沙门氏菌膜蛋白，可防止RcsC-YojN-RcsB调节系统的过度激活。该阴性对照对生长至关重要，因为igaA基因的破坏仅可能发生在rcsC、yojN或rcsB菌株中。在这项工作中，我们研究了这种调节回路对毒力的贡献。分离并表征了活的igaA点突变等位基因。这些等位基因编码IgaA变体，导致RcsC-YojN-RcsB系统的不同水平的激活。IgA介导的RcsB-YojN-RcsC系统的抑制发生在翻译后水平，如rcsC、yojN和rcsB基因的染色体表位标记所示。RcsC-YojN-RcsB系统的活性，用标记的gmd-3xFLAG基因（由RcsC-YojN-RcsB正调控）的产物监测，在小鼠靶器官中被野生型细菌完全消除。这种紧密的抑制只发生在体内，并介导的IgA。RcsC-YojN-RcsB系统的减毒是沙门氏菌毒力的必要条件，因为所有igaA点突变菌株都是高度减毒的。衰减程度与RcsC-YojN-RcsB的激活状态相关。在某些情况下，记录的衰减是前所未有的，竞争指数（CI）值低至10（-6）。引人注目的是，IgaA是一种在具有非功能性RcsC-YojN-RcsB系统的突变株中绝对不具有毒力的蛋白质。据我们所知，IgaA通过在宿主定殖后专门充当负调节剂而使第一种有助于毒力的蛋白质变性。
Bacterial pathogenesis relies on regulators that activate virulence genes. Some of them act, in addition, as repressors of specific genes. Intracellular-growth-attenuator-A (IgaA) is a Salmonella enterica membrane protein that prevents overactivation of the RcsC-YojN-RcsB regulatory system. This negative control is critical for growth because disruption of the igaA gene is only possible in rcsC, yojN or rcsB strains. In this work, we examined the contribution of this regulatory circuit to virulence. Viable igaA point mutant alleles were isolated and characterized. These alleles encode IgaA variants leading to different levels of activation of the RcsC-YojN-RcsB system. IgaA-mediated repression of the RcsB-YojN-RcsC system occurred at the post-translational level, as shown by chromosomal epitope tagging of the rcsC, yojN and rcsB genes. The activity of the RcsC-YojN-RcsB system, monitored with the product of a tagged gmd-3xFLAG gene (positively regulated by RcsC-YojN-RcsB), was totally abolished by wild-type bacteria in mouse target organs. Such tight repression occurred only in vivo and was mediated by IgaA. Shutdown of the RcsC-YojN-RcsB system is a requisite for Salmonella virulence since all igaA point mutant strains were highly attenuated. The degree of attenuation correlated to that of the activation status of RcsC-YojN-RcsB. In some cases, the attenuation recorded was unprecedented, with competitive index (CI) values as low as 10(-6). Strikingly, IgaA is a protein absolutely dispensable for virulence in mutant strains having a non-functional RcsC-YojN-RcsB system. To our knowledge, IgaA exemplifies the first protein that contributes to virulence by exclusively acting as a negative regulator upon host colonization.