Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA.
J Bacteriol. 2013 Aug;195(15):3486-502. doi: 10.1128/JB.00372-13. Epub 2013 May 31.
Haemophilus ducreyi causes chancroid, a genital ulcer disease that facilitates the transmission of human immunodeficiency virus type 1. In humans, H. ducreyi is surrounded by phagocytes and must adapt to a hostile environment to survive. To sense and respond to environmental cues, bacteria frequently use two-component signal transduction (2CST) systems. The only obvious 2CST system in H. ducreyi is CpxRA; CpxR is a response regulator, and CpxA is a sensor kinase. Previous studies by Hansen and coworkers showed that CpxR directly represses the expression of dsrA, the lspB-lspA2 operon, and the flp operon, which are required for virulence in humans. They further showed that CpxA functions predominantly as a phosphatase in vitro to maintain the expression of virulence determinants. Since a cpxA mutant is avirulent while a cpxR mutant is fully virulent in humans, CpxA also likely functions predominantly as a phosphatase in vivo. To better understand the role of H. ducreyi CpxRA in controlling virulence determinants, here we defined genes potentially regulated by CpxRA by using RNA-Seq. Activation of CpxR by deletion of cpxA repressed nearly 70% of its targets, including seven established virulence determinants. Inactivation of CpxR by deletion of cpxR differentially regulated few genes and increased the expression of one virulence determinant. We identified a CpxR binding motif that was enriched in downregulated but not upregulated targets. These data reinforce the hypothesis that CpxA phosphatase activity plays a critical role in controlling H. ducreyi virulence in vivo. Characterization of the downregulated genes may offer new insights into pathogenesis.
杜克嗜血杆菌引起软性下疳，这是一种生殖器溃疡病，可促进人类免疫缺陷病毒 1 的传播。在人体中，杜克嗜血杆菌被吞噬细胞包围，必须适应恶劣的环境才能生存。为了感知和响应环境线索，细菌经常使用双组分信号转导（2CST）系统。杜克嗜血杆菌中唯一明显的 2CST 系统是 CpxRA；CpxR 是一种反应调节剂，CpxA 是一种感应激酶。Hansen 及其同事的先前研究表明，CpxR 直接抑制 dsrA、lspB-lspA2 操纵子和 flp 操纵子的表达，这些基因对人类的毒力是必需的。他们进一步表明，CpxA 在体外主要作为磷酸酶发挥作用，以维持毒力决定因素的表达。由于 cpxA 突变体在人体内无毒性，而 cpxR 突变体完全具有毒性，因此 CpxA 在体内也可能主要作为磷酸酶发挥作用。为了更好地理解 H.ducreyi CpxRA 在控制毒力决定因素中的作用，我们使用 RNA-Seq 定义了可能受 CpxRA 调节的基因。CpxA 的缺失激活 CpxR 抑制了其近 70%的靶基因，包括七个已建立的毒力决定因素。CpxR 的缺失失活通过删除 cpxR 差异调节了少数基因，并增加了一个毒力决定因素的表达。我们鉴定了一个 CpxR 结合基序，该基序在下调但未上调的靶基因中富集。这些数据强化了 CpxA 磷酸酶活性在体内控制 H.ducreyi 毒力的假设。下调基因的特征可能为发病机制提供新的见解。
