Strong cross-system interactions drive the activation of the QseB response regulator in the absence of its cognate sensor.
Bacterial two-component systems (TCSs) mediate specific responses to distinct conditions and/or stresses. TCS interactions are highly specific between cognate partners to avoid unintended cross-talk. Although cross-talk between a sensor kinase and a noncognate response regulator has been previously demonstrated, the majority of reported interactions have not been robust. Here, we report that in the case of the quorum-sensing Escherichia coli (Qse)BC TCS, absence of the cognate sensor QseC leads to robust, constitutive activation of the QseB response regulator by the noncognate polymyxin resistance (Pmr) sensor kinase PmrB. Remarkably, the noncognate PmrB exhibits a kinetic preference for QseB that is similar to QseC. However, although PmrB readily phosphorylates QseB in vitro, it is significantly less efficient at dephosphorylating QseB, compared with QseC, thereby explaining the increased levels of active QseB in the qseC mutant. In addition to PmrB activating QseB on the protein level, we found that the PmrA response regulator contributes to qseB transcription in the absence of QseC and PmrA specifically binds the qseBC promoter, indicative of a direct regulation of qseBC gene transcription by PmrAB under physiological conditions. Addition of ferric iron in the growth medium of wild-type uropathogenic E. coli induced the expression of qseBC in a PmrB-dependent manner. Taken together, our findings suggest that (i) robust cross-talk between noncognate partners is possible and (ii) this interaction can be manipulated for the development of antivirulence strategies aimed at targeting uropathogenic Escherichia coli and potentially other QseBC-PmrAB-bearing pathogens.
['Guckes|Kirsten R|KR|', 'Kostakioti|Maria|M|', 'Breland|Erin J|EJ|', 'Gu|Alice P|AP|', 'Shaffer|Carrie L|CL|', 'Martinez|Charles R|CR|', 'Hultgren|Scott J|SJ|', 'Hadjifrangiskou|Maria|M|']
D001426:Bacterial Proteins D017931:DNA Primers D004251:DNA Transposable Elements D024202:Electrophoretic Mobility Shift Assay D004926:Escherichia coli D029968:Escherichia coli Proteins D015964:Gene Expression Regulation, Bacterial D015151:Immunoblotting D016296:Mutagenesis D053038:Quorum Sensing D060888:Real-Time Polymerase Chain Reaction D020239:Receptor Cross-Talk D015398:Signal Transduction
phosphorylation UPEC regulatory networks signal transduction