Distinctive Regulation of Carbapenem Susceptibility in Pseudomonas aeruginosa by Hfq

Abstract

Carbapenems are often the antibiotics of choice to combat life threatening infections caused by the opportunistic human pathogen Pseudomonas aeruginosa. The outer membrane porins OprD and OpdP serve as entry ports for carbapenems. Here, we report that the RNA chaperone Hfq governs post-transcriptional regulation of the oprD and opdP genes in a distinctive manner. Hfq together with the recently described small regulatory RNAs (sRNAs) ErsA and Sr0161 is shown to mediate translational repression of oprD, whereas opdP appears not to be regulated by sRNAs. At variance, our data indicate that opdP is translationally repressed by a regulatory complex consisting of Hfq and the catabolite repression protein Crc, an assembly known to be key to carbon catabolite repression in P. aeruginosa. The regulatory RNA CrcZ, which is up-regulated during growth of P. aeruginosa on less preferred carbon sources, is known to sequester Hfq, which relieves Hfq-mediated translational repression of genes. The differential carbapenem susceptibility during growth on different carbon sources can thus be understood in light of Hfq-dependent oprD/opdP regulation and of the antagonizing function of the CrcZ RNA on Hfq regulatory complexes.

Specific and Global RNA Regulators in Pseudomonas aeruginosa

“…It acts as a pleiotro post-transcriptional regulator, which, in Pseudomonads, can act in concert with the cata lite repression control protein Crc [142,[146][147][148]. Hfq-dependent regulation controls tabolism [29] and virulence traits [47,51,124,[149][150][151], including the susceptibility to cl cally relevant antibiotics (Figure 3a) [52,75,152]. As mentioned above, Hfq can exert th functions by aiding riboregulation by sRNAs [47,51,52,153], but also by directly repress the translation of target mRNAs containing cognate Hfq-binding motifs [29,151].…”

“…In addition, Sr0161 was suggested to regulate opdP mRNA, which encodes a second porin involved in carbapenem uptake [52]. However, recent studies revealed that opdP appears not to be regulated by sRNAs [75]. At variance, opdP appeared to be translationally repressed by a regulatory complex consisting of Hfq and the catabolite repression protein Crc (see below).…”

“…Hence, the sequestration of Hfq by CrcZ/Y prevents Hfq from binding to target mRNAs and results in translational de-repression [29,147,196,197,205]. In addition, through the competition for Hfq, CrcZ can also interfere with Hfq-dependent riboregulation by sRNAs [47] and hence, indirectly cross-regulate other physiologically important processes such as biofilm formation [199] and antibiotic susceptibility [75,152] (Figure 3).…”

A Grad-seq view of RNA and protein complexes inPseudomonas aeruginosaunder standard and bacteriophage predation conditions

“…ErsA is a well-characterized small RNA of P. aeruginosa, which has been proposed to serve a dual regulatory role in biofilm development, activating the mRNA of transcriptional regulator AmrZ while at the same time repressing the mRNA of AlgC, an important virulenceassociated enzyme for the production of sugar precursors (71,72). In addition, ErsA acts as a translational repressor of the mRNA of outer membrane porin OprD (73). ErsA is wellexpressed during the exponential growth phase (51) and bound by Hfq (8), making it an excellent candidate for validation by an independent technique of the infection-dependent changes seen in Grad-seq.…”

The Impact of an Efflux Pump Inhibitor on the Activity of Free and Liposomal Antibiotics against Pseudomonas aeruginosa

“…Poor drug penetration is a major issue behind bacterial resistance to antibiotics. It can be attributable to reduced membrane permeability to antibiotics [ 14 ] and to the expression of efflux pumps which thwart the activity of antimicrobials by inducing their expulsion from the cell [ 15 , 16 , 17 , 18 ].…”