CcpA-mediated repression of streptolysin S expression and virulence in the group a streptococcus
CcpA-mediated repression of streptolysin S expression and virulence in the group a streptococcus
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DOI：
10.1128/iai.00343-08
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发表时间：
2008-08-01
影响因子：
3.1
通讯作者：
McIver, Kevin S.
中科院分区：
文献类型：
--
作者：
Kinkel, Traci L.;McIver, Kevin S.
CcpA是革兰氏阳性菌中碳分解代谢产物抑制（CCR）的全局介质，并且来自包括A组链球菌（GAS）在内的几种病原体的越来越多的证据表明CcpA在毒力基因调控中起重要作用。在这项研究中，在侵袭性M1 GAS菌株中缺失ccpA用于测试CcpA对小鼠发病机制的贡献。令人惊讶的是，与亲本MGAS 5005菌株相比，Delta ccpA突变体表现出显著的“高毒力”表型，反映为在全身感染（腹膜内施用）模型中增加的致死率和在皮肤感染（皮下施用）模型中更大的病变尺寸。从其天然启动子的反式ccpA的表达能够补充两种表型，表明CcpA的作用，以抑制GAS的毒力。为了鉴定所涉及的CcpA调节基因，对在丰富培养基中生长的对数期中期细胞进行转录组分析。发现CcpA主要抑制6%的GAS基因组（124个基因），包括参与糖代谢、转录调控和毒力的基因。值得注意的是，链球菌溶血素S（SLS）生产所需的整个sag操纵子在CcpA介导的CCR下，SLS溶血活性也是如此。纯化的CcpA-His特异性结合到sagAp内的cre，表明直接抑制操纵子。最后，SLS活性是在全身感染期间增加Delta ccpA突变体的毒力所必需的，但不影响野生型背景中的毒力。因此，CcpA在小鼠全身感染过程中抑制SLS活性和毒力，揭示了碳代谢和GAS发病机制之间的重要联系。
CcpA is the global mediator of carbon catabolite repression (CCR) in gram-positive bacteria, and growing evidence from several pathogens, including the group A streptococcus (GAS), suggests that CcpA plays an important role in virulence gene regulation. In this study, a deletion of ccpA in an invasive M1 GAS strain was used to test the contribution of CcpA to pathogenesis in mice. Surprisingly, the Delta ccpA mutant exhibited a dramatic "hypervirulent" phenotype compared to the parental MGAS5005 strain, reflected as increased lethality in a model of systemic infection (intraperitoneal administration) and larger lesion size in a model of skin infection (subcutaneous administration). Expression of ccpA in trans from its native promoter was able to complement both phenotypes, suggesting that CcpA acts to repress virulence in GAS. To identify the CcpA-regulated genet(s) involved, a transcriptome analysis was performed on mid-logarithmic-phase cells grown in rich medium. CcpA was found to primarily repress 6% of the GAS genome (124 genes), including genes involved in sugar metabolism, transcriptional regulation, and virulence. Notably, the entire sag operon necessary for streptolysin S (SLS) production was under CcpA-mediated CCR, as was SLS hemolytic activity. Purified CcpA-His bound specifically to a cre within sagAp, demonstrating direct repression of the operon. Finally, SLS activity is required for the increased virulence of a Delta ccpA mutant during systemic infection but did not affect virulence in a wild-type background. Thus, CcpA acts to repress SLS activity and virulence during systemic infection in mice, revealing an important link between carbon metabolism and GAS pathogenesis.