title: AmgRS-mediated envelope stress-inducible expression of the mexXY multidrug efflux operon of Pseudomonas aeruginosa.
abstract: AmgRS is an envelope stress-responsive two-component system and aminoglycoside resistance determinant in Pseudomonas aeruginosa that is proposed to protect cells from membrane damage caused by aminoglycoside-generated mistranslated polypeptides. Consistent with this, a ΔamgR strain showed increased aminoglycoside-promoted membrane damage, damage that was largely absent in AmgRS-activated amgS-mutant strains. Intriguingly, one such mutation, V121G, while providing for enhanced resistance to aminoglycosides, rendered P. aeruginosa susceptible to several ribosome-targeting nonaminoglycoside antimicrobials that are inducers and presumed substrates of the MexXY-OprM multidrug efflux system. Surprisingly, the amgSV 121G mutation increased mexXY expression threefold, suggesting that export of these nonaminoglycosides was compromised in the amgSV 121G mutant. Nonetheless, a link was established between AmgRS activation and mexXY expression and this was confirmed in studies showing that aminoglycoside-promoted mexXY expression is dependent on AmgRS. While nonaminoglycosides also induced mexXY expression, this was not AmgRS-dependent, consistent with these agents not generating mistranslated polypeptides and not activating AmgRS. The aminoglycoside inducibility of mexXY was abrogated in a mutant lacking the AmgRS target genes htpX and PA5528, encoding a presumed cytoplasmic membrane-associated protease and a membrane protein of unknown function, respectively. Thus, aminoglycoside induction of mexXY is a response to membrane damage and activation of the AmgRS two-component system.
authors.affiliation: Department of Biomedical and Molecular Sciences, Botterell Hall, Queen's University, Kingston, Ontario, K7L 3N6, Canada. calvin.lau@agr.gc.ca.
authors.forename: Calvin Ho-Fung
authors.initials: CH
authors.lastname: Lau
authors.forename: Thomas
authors.initials: T
authors.lastname: Krahn
authors.forename: Christie
authors.initials: C
authors.lastname: Gilmour
authors.forename: Erin
authors.initials: E
authors.lastname: Mullen
authors.forename: Keith
authors.initials: K
authors.lastname: Poole
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D019450:Genes, MDR; D009154:Mutation; D009876:Operon; D021381:Protein Transport; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics*; D013312:Stress, Physiological / Q000235:genetics
chemical_list: D000617:Aminoglycosides; D001426:Bacterial Proteins; C402791:MexXY protein, Pseudomonas aeruginosa
keywords: Efflux; Pseudomonas aeruginosa; envelope stress; multidrug; two-component system