Reserpine Is the New Addition into the Repertoire of AcrB Efflux Pump Inhibitors
Acriflavine resistance protein B (AcrB) serves as prototype for multidrug resistance (MDR) efflux transporters of resistance nodulation division (RND) superfamily. AcrB has been proven as potential drug target with many synthetic and natural inhibitors have been identified such as those belonging to pyranopyridine, naphthamide and pimozide classes. The plant derived alkaloid inhibitors represented by reserpine has been found to inhibit both ATP binding cassette and major facilitator efflux transporters. In this study we report the reserpine induced inhibition of RND transporter AcrB. The preliminary docking analysis hints that reserpine shares its binding site with ciprofloxacin, a known substrate of AcrB and could possibly act as competitive inhibitor. For in vitro validation, AcrB from Salmonellatyphi was cloned under the control of tac promoter and resulting vector was introduced into E. coli C41(DE3). Under autoinduced conditions, cells overexpressing AcrB transporter were subjected to combined dose of ciprofloxacin and reserpine. The combined exposure resulted in enhanced ciprofloxacin-induced growth inhibition of cells expressing AcrB transporter as compared to control cells transformed with vector of backbone sequence. Time kill analysis further confirmed these findings. To the best of our knowledge, this is first study to show that exposure to reserpine induces inhibition of AcrB. The assay developed in this study allows simple and reproducible detection of substrate/inhibitor effects upon AcrB and related efflux transporters.
Keywords:acriflavine resistance protein resistance nodulation division transporter reserpine ciprofloxacin multidrug resistance Salmonellatyphi
This research work was funded by the Higher Education Commission of Pakistan (grant no. 20-1504 to M. Rahman).
COMPLIANCE WITH ETHICAL STANDARDS
The authors declare that they have no conflict of interest. This article does not contain any studies involving animals or human participants performed by any of the authors.
W.A. Afridia and S. Mahbooba are both equally contributed to this work.
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