Understanding polyspecificity within the substrate-binding cavity of the human multidrug resistance P-glycoprotein.
Human P-glycoprotein (P-gp) controls drugs bioavailability by pumping structurally unrelated drugs out of cells. The X-ray structure of the mouse P-gp ortholog has been solved, with two SSS enantiomers or one RRR enantiomer of the selenohexapeptide inhibitor QZ59, found within the putative drug-binding pocket (Aller SG, Yu J, Ward A, Weng Y, Chittaboina S, Zhuo R, Harrell PM, Trinh YT, Zhang Q, Urbatsch IL et al. (2009). Science 323, 1718-1722). This offered the first opportunity to localize the well-known H and R drug-binding sites with respect to the QZ59 inhibition mechanisms of Hoechst 33342 and daunorubicin transports, characterized here in cellulo. We found that QZ59-SSS competes efficiently with both substrates, with K(I,app) values of 0.15 and 0.3 μM, which are 13 and 2 times lower, respectively, than the corresponding K(m,app) values. In contrast, QZ59-RRR non-competitively inhibited daunorubicin transport with moderate efficacy (K(I,app) = 1.9 μM); it also displayed a mixed-type inhibition of the Hoechst 33342 transport, resulting from a main non-competitive tendency (K(i2,app) = 1.6 μM) and a limited competitive tendency (K(i1,app) = 5 μM). These results suggest a positional overlap of QZ59 and drugs binding sites: full for the SSS enantiomer and partial for the RRR enantiomer. Crystal structure analysis suggests that the H site overlaps both QZ59-SSS locations while the R site overlaps the most embedded location.
Drug Resistance Mechanism and Modulation group, Ligue 2013 certified, Molecular and Structural Basis of Infectious Systems, Mixed Research Unit between the National Centre for Scientific Research and Lyon I University n°5086, Institute of Biology and Chemistry of Proteins, France.
Lorena
L
Martinez
Ophélie
O
Arnaud
Emilie
E
Henin
Houchao
H
Tao
Vincent
V
Chaptal
Rupak
R
Doshi
Thibault
T
Andrieu
Sébastien
S
Dussurgey
Michel
M
Tod
Attilio
A
Di Pietro
Qinghai
Q
Zhang
Geoffrey
G
Chang
Pierre
P
Falson
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D001562:Benzimidazoles / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D001692:Biological Transport / Q000187:drug effects; D020134:Catalytic Domain; D003630:Daunorubicin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D006801:Humans; D007700:Kinetics; D049990:Membrane Transport Modulators / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D051379:Mice; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D041681:NIH 3T3 Cells; D010456:Peptides, Cyclic / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism
C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D001562:Benzimidazoles; D049990:Membrane Transport Modulators; D010456:Peptides, Cyclic; D020033:Protein Isoforms; D011994:Recombinant Proteins; C539646:cyclic-tris-(R)-valineselenazole; C017807:bisbenzimide ethoxide trihydrochloride; D003630:Daunorubicin
ABC transporters; P-glycoprotein; cancer; drug efflux; drug resistance; drug-binding sites