title: Activation of CpxRA in Haemophilus ducreyi primarily inhibits the expression of its targets, including major virulence determinants.
abstract: 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.
authors.affiliation: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, USA. dgangaia@iupui.edu
authors.forename: Dharanesh
authors.initials: D
authors.lastname: Gangaiah
authors.forename: Xinjun
authors.initials: X
authors.lastname: Zhang
authors.forename: Kate R
authors.initials: KR
authors.lastname: Fortney
authors.forename: Beth
authors.initials: B
authors.lastname: Baker
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Liu
authors.forename: Robert S
authors.initials: RS
authors.lastname: Munson
authors.forename: Stanley M
authors.initials: SM
authors.lastname: Spinola
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006191:Haemophilus ducreyi / Q000235:genetics*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D018085:Regulon; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D037521:Virulence Factors / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D037521:Virulence Factors; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; C092472:CpxA protein, bacteria; D010749:Phosphoprotein Phosphatases