A bacterial antibiotic-resistance gene that complements the human multidrug-resistance P-glycoprotein gene

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Bacteria have developed many fascinating antibiotic-resistance mechanisms1,2. A protein in Lactococcus lactis, LmrA, mediates antibiotic resistance by extruding amphiphilic compounds from the inner leaflet of the cytoplasmic membrane3,4. Unlike other known bacterial multidrug-resistance proteins, LmrA is an ATP-binding cassette (ABC) transporter5. The human multidrug-resistance P-glycoprotein6, encoded by the MDR1 gene, is also an ABC transporter, overexpression of which is one of the principal causes of resistance of human cancers to chemotherapy7,8. We expressed lmrA in human lung fibroblast cells. Surprisingly, LmrA was targeted to the plasma membrane and conferred typical multidrug resistance on these human cells. The pharmacological characteristics of LmrA and P-glycoprotein-expressing lung fibroblasts were very similar, and the affinities of both proteins for vinblastine and magnesium-ATP were indistinguishable. Blockers of P-glycoprotein-mediated multidrug resistance also inhibited LmrA-dependent drug resistance. Kinetic analysis of drug dissociation from LmrA expressed in plasma membranes of insect cells revealed the presence of two allosterically linked drug-binding sites indistinguishable from those of P-glycoprotein. These findings have implications for the reversal of antibiotic resistance in pathogenic microorganisms. Taken together, they demonstrate that bacterial LmrA and human P-glycoprotein are functionally interchangeable and that this type of multidrug-resistance efflux pump is conserved from bacteria to man.

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Figure 1: Expression of LmrA in GM0637 human lung fibroblast cells.
Figure 2: Drug-resistance phenotypes generated by LmrA expression in GM0637 human lung fibroblast cells.
Figure 3: Wild-type LmrA protein functions as a multidrug transporter in GM0637 human lung fibroblast cells.
Figure 4: Pharmacological properties of wild-type LmrA and human P-glycoprotein expressed in insect cell membranes.


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We are grateful to Sahofi Recherche for supplying SR33557. We thank M. Müller for anti-MRP1 antibody K5, D. Gill for plasmid pKSMDR1, and J. Taylor, K. Linton, E. Blott, G. Berridge, C.Martin, G. Begley, R. Horvath, C. Nastrucci, S. Hyde, D. Gill and P. A. McNaughton for discussions. This research was funded by the Biotechnology program of the Commission of the European Communities, the Dutch Cancer Society, the Cancer Research Campaign (UK), and the Imperial Cancer Research Fund. H.W.V.V. was the recipient of a short-term EMBO fellowship, and is a fellow of the Royal Netherlands Academy of Arts and Sciences. C.F.H. is a Howard Hughes international Research Scholar.

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Correspondence to Hendrik W. van Veen.

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