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Taylor AM, Storm J, Soceneantu L, Linton KJ, Gabriel M, Martin C, Woodhouse J, Blott E, Higgins CF, Callaghan R. Detailed characterization of cysteine-less P-glycoprotein reveals subtle pharmacological differences in function from wild-type protein. Br J Pharmacol 2001; 134:1609-18. [PMID: 11739236 PMCID: PMC1572892 DOI: 10.1038/sj.bjp.0704400] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
1. Subtle alterations in the coupling of drug binding to nucleotide hydrolysis were observed following mutation of all seven endogenous cysteine residues to serines in the human multidrug resistance transporter, P-glycoprotein. Wild-type (wt) and the mutant (cys-less) forms of P-gp were expressed in Trichoplusia ni (High Five) cells and purified by metal affinity chromatography in order to undertake functional studies. 2. No significant differences were observed in substrate ([(3)H]-azidopine) binding to wt or cys-less P-gp. Furthermore, neither the transported substrate vinblastine, nor the modulator nicardipine, differed in their respective potencies to displace [(3)H]-azidopine from the wt or cys-less P-gp. These results suggest that respective binding sites for these drugs were unaffected by the introduced cysteine to serine substitutions. 3. The Michaelis-Menten characteristics of basal ATP hydrolysis of the two isoforms of P-gp were identical. The maximal ATPase activity in the presence of vinblastine was marginally reduced whilst the K(m) was unchanged in cys-less P-gp compared to control. However, cys-less P-gp displayed lower overall maximal ATPase activity (62%), a decreased K(m) and a lower degree of stimulation (76%) in the presence of the modulator nicardipine. 4. Therefore, the serine to cysteine mutations in P-gp may suggest that vinblastine and nicardipine transduce their effects on ATP hydrolysis through distinct conformational pathways. The wt and cys-less P-gp isoforms display similarity in their fundamental kinetic properties thereby validating the use of cys-less P-gp as a template for future cysteine-directed structure/function analysis.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP Binding Cassette Transporter, Subfamily B, Member 1/physiology
- Adenosine Triphosphatases/metabolism
- Adenosine Triphosphate/metabolism
- Animals
- Azides/metabolism
- Baculoviridae/genetics
- Binding Sites
- Cell Membrane/metabolism
- Cells, Cultured
- Cross-Linking Reagents/chemistry
- Cysteine/genetics
- Dihydropyridines/metabolism
- Dose-Response Relationship, Drug
- Drug Resistance, Multiple
- Humans
- Inhibitory Concentration 50
- Kinetics
- Mutagenesis
- Nicardipine/pharmacology
- Photoaffinity Labels/metabolism
- Serine/genetics
- Spodoptera/virology
- Vinblastine/pharmacology
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Affiliation(s)
- Andrew M Taylor
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
| | - Janet Storm
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
| | - Loredana Soceneantu
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
| | - Kenneth J Linton
- MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN
| | - Mark Gabriel
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
| | - Catherine Martin
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
| | - James Woodhouse
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
| | - Emma Blott
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
| | - Christopher F Higgins
- MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN
| | - Richard Callaghan
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU
- Author for correspondence:
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