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bioRxiv · 10.1101/2023.08.14.553335

Pseudomonas aeruginosa MipA-MipB envelope proteins act as new sensors of polymyxin

Janet-Maitre, M.·Job, V.·Bour, M.·Brugiere, S. M.·Robert-Genthon, M.·Cobessi, D.·Coute, Y.·Jeannot, K.·Attree, I.
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Abstract

Due to the rising incidence of antibiotic resistant infections, the last-line antibiotics polymyxins have resurged in the clinics in parallel with new bacterial strategies of escape. The Gram-negative opportunistic pathogen Pseudomonas aeruginosa develops resistance to colistin/polymyxin by distinct molecular mechanisms, mostly through modification of the lipid A component of the LPS by proteins encoded within the arnBCDATEF-ugd (arn) operon. In this work, we characterized a polymyxin-induced operon, named mipBA, notably present in P. aeruginosa strains devoid of the arn operon. We showed that mipBA is activated by ParR/ParS two-component regulatory system in response to polymyxin. MipA and MipB localize to bacterial outer membrane and form a complex in vitro. Structural modeling revealed that the lipoprotein MipB adopts a {beta}-lactamase fold with two additional C-terminal domains,while MipA folds as an outer-membrane {beta}-barrel, harboring an internal negatively charged channel, able to host a polymyxin molecule. Nano differential scanning fluorimetry (DSF) showed that polymyxin stabilized MipA protein in vitro. Mass spectrometry-based quantitative proteomics on whole bacterial membranes demonstrated that the {Delta}mipBA mutant synthesized less MexXY-OprA proteins in response to polymyxin compared to the wild-type strain, as a consequence of impaired transcriptional activation of the mex operon. We propose MipA/MipB to act as membrane (co)sensors working in concert to activate ParS histidine kinase and help the bacterium to cope with polymyxin-mediated envelope stress through synthesis of the efflux pomp, MexXY-OprA.

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Janet-Maitre, M., Job, V., Bour, M., Brugiere, S. M., Robert-Genthon, M., Cobessi, D., Coute, Y., Jeannot, K., Attree, I.. 2023-08-15. Pseudomonas aeruginosa MipA-MipB envelope proteins act as new sensors of polymyxin. https://doi.org/10.1101/2023.08.14.553335

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