title: The CpxR/CpxA two-component regulatory system up-regulates the multidrug resistance cascade to facilitate Escherichia coli resistance to a model antimicrobial peptide.
abstract: A genome-wide susceptibility assay was used to identify specific CpxR-dependent genes that facilitate Escherichia coli resistance to a model cationic antimicrobial peptide, protamine. A total of 115 strains from the Keio Collection, each of which contained a deletion at a demonstrated or predicted CpxR/CpxA-dependent locus, were tested for protamine susceptibility. One strain that exhibited high susceptibility carried a deletion of tolC, a gene that encodes the outer membrane component of multiple tripartite multidrug transporters. Concomitantly, two of these efflux systems, AcrAB/TolC and EmrAB/TolC, play major roles in protamine resistance. Activation of the CpxR/CpxA system stimulates mar transcription, suggesting a new regulatory circuit that enhances the multidrug resistance cascade. Tripartite multidrug efflux systems contribute to bacterial resistance to protamine differently from the Tat system. DNase I footprinting analysis demonstrated that the CpxR protein binds to a sequence located in the -35 and -10 regions of mar promoter. This sequence resembles the consensus CpxR binding site, however, on the opposite strand. aroK, a CpxR-dependent gene that encodes a shikimate kinase in the tryptophan biosynthesis pathway, was also found to facilitate protamine resistance. Specific aromatic metabolites from this pathway, such as indole, can stimulate expression of well studied CpxR-dependent genes degP and cpxP, which are not components of the tripartite multidrug transporters. Thus, we propose a novel mechanism for E. coli to modulate resistance to protamine and likely other cationic antimicrobial peptides in which the CpxR/CpxA system up-regulates mar transcription in response to specific aromatic metabolites, subsequently stimulating the multidrug resistance cascade.
authors.affiliation: From The School of Life Sciences.
authors.forename: Natasha
authors.initials: N
authors.lastname: Weatherspoon-Griffin
authors.affiliation: the College of Life Sciences, Inner Mongolia University, Hohhot, Inner Mongolia 010021, China, and From The School of Life Sciences, The Center for Infectious Diseases and Vaccinology at the Biodesign Institute, Arizona State University, Tempe, Arizona, 85287-4501.
authors.forename: Dezhi
authors.initials: D
authors.lastname: Yang
authors.affiliation: The Center for Infectious Diseases and Vaccinology at the Biodesign Institute, Arizona State University, Tempe, Arizona, 85287-4501.
authors.forename: Wei
authors.initials: W
authors.lastname: Kong
authors.affiliation: The State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, Jiangsu, 210093, China.
authors.forename: Zichun
authors.initials: Z
authors.lastname: Hua
authors.affiliation: From The School of Life Sciences, The Center for Infectious Diseases and Vaccinology at the Biodesign Institute, Arizona State University, Tempe, Arizona, 85287-4501, yixin.shi@asu.edu.
authors.forename: Yixin
authors.initials: Y
authors.lastname: Shi
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D050296:Microbial Viability / Q000187:drug effects / Q000235:genetics; D008957:Models, Genetic; D009154:Mutation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011479:Protamines / Q000494:pharmacology*; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D015854:Up-Regulation
chemical_list: D023181:Antimicrobial Cationic Peptides; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; C080004:MarR protein, E coli; D026901:Membrane Transport Proteins; D011479:Protamines; D012097:Repressor Proteins; C073126:tolC protein, E coli; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); C022642:shikimate kinase; C490475:CpxA protein, E coli
keywords: Bacterial Signal Transduction; CpxR Box; Multidrug Transporter; The CpxR/CpxA Two-Component System; The mar Operon; Transcription Factor; Transcription Promoter; Transcription Regulation