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A bacterial antibiotic-resistance gene that complements the human multidrug-resistance P-glycoprotein gene
H W van Veen1, R Callaghan, L Soceneantu
1Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands. h.w.van.veen@biol.rug.nl
Abstract:
Bacteria have developed many fascinating antibiotic-resistance mechanisms. A protein in Lactococcus lactis, LmrA, mediates antibiotic resistance by extruding amphiphilic compounds from the inner leaflet of the cytoplasmic membrane. Unlike other known bacterial multidrug-resistance proteins, LmrA is an ATP-binding cassette (ABC) transporter. The human multidrug-resistance P-glycoprotein, 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 chemotherapy. 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.
Insights
Bacterial antibiotic resistance protein LmrA functions like human P-glycoprotein. Expressing LmrA in human cells conferred multidrug resistance, showing conserved drug efflux pump mechanisms from bacteria to humans.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- Bacteria develop antibiotic resistance through various mechanisms.
- Lactococcus lactis protein LmrA extrudes compounds, conferring antibiotic resistance.
- LmrA is an ATP-binding cassette (ABC) transporter, unlike other bacterial multidrug-resistance proteins.
Purpose of the Study:
- To investigate the function and characteristics of bacterial LmrA in human cells.
- To compare LmrA's drug resistance mechanisms with human P-glycoprotein.
- To explore the conservation of multidrug-resistance efflux pumps across species.
Main Methods:
- Expressed bacterial lmrA gene in human lung fibroblast cells.
- Assessed drug resistance phenotypes in engineered human cells.
- Compared pharmacological properties and drug-binding sites of LmrA and human P-glycoprotein.
Main Results:
- LmrA localized to the plasma membrane of human cells and conferred multidrug resistance.
- LmrA and P-glycoprotein showed similar affinities for vinblastine and magnesium-ATP.
- Inhibitors of P-glycoprotein also blocked LmrA-mediated drug resistance.
- Kinetic analysis revealed two allosterically linked drug-binding sites in LmrA, identical to P-glycoprotein.
Conclusions:
- Bacterial LmrA and human P-glycoprotein are functionally interchangeable.
- The multidrug-resistance efflux pump mechanism is conserved from bacteria to humans.
- Findings suggest potential strategies for reversing antibiotic resistance in pathogens.