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Bin Dayel A, Evans RJ, Schmid R. Mapping the Site of Action of Human P2X7 Receptor Antagonists AZ11645373, Brilliant Blue G, KN-62, Calmidazolium, and ZINC58368839 to the Intersubunit Allosteric Pocket. Mol Pharmacol 2019; 96:355-363. [PMID: 31263019 PMCID: PMC6701605 DOI: 10.1124/mol.119.116715] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 06/21/2019] [Indexed: 12/14/2022] Open
Abstract
The P2X7 receptor is a trimeric ligand-gated ion channel activated by ATP. It is implicated in the cellular response to trauma/disease and considered to have significant therapeutic potential. Using chimeras and point mutants we have mapped the binding site of the P2X7R-selective antagonist AZ11645373 to the known allosteric binding pocket at the interface between two subunits, in proximity to, but separated from the ATP binding site. Our structural model of AZ11645373 binding is consistent with effects of mutations on antagonist sensitivity, and the proposed binding mode explains variation in antagonist sensitivity between the human and rat P2X7 receptors. We have also determined the site of action for the P2X7R-selective antagonists ZINC58368839, brilliant blue G, KN-62, and calmidazolium. The effect of intersubunit allosteric pocket “signature mutants” F88A, T90V, D92A, F103A, and V312A on antagonist sensitivity suggests that ZINC58368839 comprises a binding mode similar to AZ11645373 and other previously characterized antagonists. For the larger antagonists, brilliant blue G, KN-62, and calmidazolium, our data imply an overlapping but distinct binding mode involving the central upper vestibule of the receptor in addition to the intersubunit allosteric pocket. Our work explains the site of action for a series of P2X7R antagonists and establishes “signature mutants” for P2X7R binding-mode characterization.
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Affiliation(s)
- Anfal Bin Dayel
- Department of Molecular and Cell Biology (A.B.D., R.J.E., R.S.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom
| | - Richard J Evans
- Department of Molecular and Cell Biology (A.B.D., R.J.E., R.S.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom
| | - Ralf Schmid
- Department of Molecular and Cell Biology (A.B.D., R.J.E., R.S.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom
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Allsopp RC, Dayl S, Bin Dayel A, Schmid R, Evans RJ. Mapping the Allosteric Action of Antagonists A740003 and A438079 Reveals a Role for the Left Flipper in Ligand Sensitivity at P2X7 Receptors. Mol Pharmacol 2018. [PMID: 29535152 PMCID: PMC5896373 DOI: 10.1124/mol.117.111021] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
P2X7 receptor (P2X7R) activation requires ∼100-fold higher concentrations of ATP than other P2X receptor (P2XR) subtypes. Such high levels are found during cellular stress, and P2X7Rs consequently contribute to a range of pathophysiological conditions. We have used chimeric and mutant P2X7Rs, coupled with molecular modeling, to produce a validated model of the binding mode of the subtype-selective antagonist A438079 at an intersubunit allosteric site. Within the allosteric site large effects on antagonist action were found for point mutants of residues F88A, D92A, F95A, and F103A that were conserved or similar between sensitive/insensitive P2XR subtypes, suggesting that these side-chain interactions were not solely responsible for high-affinity antagonist binding. Antagonist sensitivity was increased with mutations that remove the bulk of side chains around the center of the binding pocket, suggesting that the dimensions of the pocket make a significant contribution to selectivity. Chimeric receptors swapping the left flipper (around the orthosteric site) reduced both ATP and antagonist sensitivity. Point mutations within this region highlighted the contribution of a P2X7R-specific aspartic acid residue (D280) that modeling suggests forms a salt bridge with the lower body region of the receptor. The D280A mutant removing this charge increased ATP potency 15-fold providing a new insight into the low ATP sensitivity of the P2X7R. The ortho- and allosteric binding sites form either side of the β-strand Y291-E301 adjacent to the left flipper. This structural linking may explain the contribution of the left flipper to both agonist and antagonist action.
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Affiliation(s)
- Rebecca C Allsopp
- Department of Molecular and Cell Biology (R.C.A., S.D., A.B.D., R.S., R.J.E.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom; and Department of Chemistry, College of Science, University of Baghdad, Baghdad, Iraq (S.D.)
| | - Sudad Dayl
- Department of Molecular and Cell Biology (R.C.A., S.D., A.B.D., R.S., R.J.E.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom; and Department of Chemistry, College of Science, University of Baghdad, Baghdad, Iraq (S.D.)
| | - Anfal Bin Dayel
- Department of Molecular and Cell Biology (R.C.A., S.D., A.B.D., R.S., R.J.E.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom; and Department of Chemistry, College of Science, University of Baghdad, Baghdad, Iraq (S.D.)
| | - Ralf Schmid
- Department of Molecular and Cell Biology (R.C.A., S.D., A.B.D., R.S., R.J.E.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom; and Department of Chemistry, College of Science, University of Baghdad, Baghdad, Iraq (S.D.)
| | - Richard J Evans
- Department of Molecular and Cell Biology (R.C.A., S.D., A.B.D., R.S., R.J.E.) and Leicester Institute of Structural and Chemical Biology (R.S.), University of Leicester, Leicester, United Kingdom; and Department of Chemistry, College of Science, University of Baghdad, Baghdad, Iraq (S.D.)
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