An outer membrane protease of the omptin family prevents activation of the Citrobacter rodentium PhoPQ two-component system by antimicrobial peptides.
The PhoPQ two-component system of the intracellular pathogen Salmonella enterica senses and controls resistance to alpha-helical antimicrobial peptides (AMPs) by regulating covalent modifications of lipid A. A homologue of the phoPQ operon was found in the genome of the murine enteric extracellular pathogen, Citrobacter rodentium. Here we report that C. rodentium PhoPQ was apparently unable to mediate activation of target genes in the presence of alpha-helical AMPs. However, these AMPs activated C. rodentium PhoPQ expressed in a S. entericaDeltaphoPQ mutant. Analysis of the outer membrane (OM) fractions of the C. rodentium wild-type and DeltaphoPQ strains led to the identification of an omptin family protease (CroP) that was absent in DeltaphoPQ. Deletion of croP in C. rodentium resulted in higher susceptibility to alpha-helical AMPs, indicating a direct role of CroP in AMP resistance. CroP greatly contributed to the protection of the OM from AMP damage by actively degrading alpha-helical AMPs before they reach the periplasmic space. Accordingly, transcriptional activation of PhoP-regulated genes by alpha-helical AMPs was restored in the DeltacroP mutant. This study shows that resistance to alpha-helical AMPs by the extracellular pathogen C. rodentium relies primarily on the CroP OM protease.
Le Sage
Valerie
V
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
Zhu
Lei
L
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
Lepage
Christine
C
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
Portt
Andrea
A
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
Viau
Charles
C
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
Daigle
France
F
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
Gruenheid
Samantha
S
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
Le Moual
Hervé
H
Department of Microbiology and Immunology andFaculty of Dentistry, McGill University, Montreal, QC, H3A 2B4, Canada.Department of Microbiology and Immunology, University of Montreal, Montreal, QC, H3C 3J7, Canada.
D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D044082:Citrobacter rodentium / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D012329:RNA, Bacterial / Q000235:genetics; D012697:Serine Endopeptidases / Q000235:genetics / Q000378:metabolism*
D023181:Antimicrobial Cationic Peptides; D001426:Bacterial Proteins; C079792:PhoQ protein, Bacteria; D012329:RNA, Bacterial; C061064:PhoP protein, Bacteria; D012697:Serine Endopeptidases; C057840:omptin outer membrane protease; D008274:Magnesium