Abstract
There are currently seven P2X receptor subunits (P2X1–7) defined by molecular cloning. The functional identification of these receptors has relied primarily on the potency of α,β-methylene-ATP relative to that of ATP and on the kinetics of receptor desensitization. In the present experiments we found that the 2′,3′-O-(2,4,6-trinitrophenyl)-substituted analogs of ATP are selective and potent antagonists at some but not all P2X receptors. The trinitrophenyl analogs of ATP, ADP, AMP, and GTP produced a reversible inhibition of ATP-evoked currents in human embryonic kidney 293 cells expressing P2X1 receptors, P2X3 receptors, or both P2X2 and P2X3 (heteromeric) receptors; IC50 values were close to 1 nm. These compounds were at least 1000-fold less effective in blocking currents in cells expressing P2X2, P2X4, or P2X7receptors (P2X5 and P2X6 not tested). GTP, 2,4,6-trinitrophenol, and the 2′,3′-trinitrophenyl analog of adenosine (0.1–10 μm) had no effect. Thus, we have identified a structural motif that confers antagonist action at P2X receptors that contain P2X1 or P2X3 subunits (the α,β-methylene-ATP-sensitive subclass).
Footnotes
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Send reprint requests to: Dr. R. A. North, Institute of Molecular Pharmacology, Department of Biomedical Sciences, University of Sheffield, Alfred Denny Building, Sheffield SIO 2TN, England, UK. E-mail: r.a.north{at}sheffield.ac.uk
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↵1 Current affiliation: Department of Pharmacology, Glaxo Wellcome Research and Development, 37135 Verona, Italy
- Abbreviations:
- αβmeATP
- α,β-methylene-ATP
- HEK
- human embryonic kidney
- HEPES
- 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- PPADS
- pyridoxal 5-phosphate 6-azophenyl-2′,4′-disulphonic acid
- TNP
- trinitrophenyl
- TNP-A
- 2′,3′-O-(2,4,6-trinitrophenyl)-adenosine
- TNP-ADP
- 2′,3′-O-(2,4,6-trinitrophenyl)-ADP
- TNP-AMP
- 2′,3′-O-(2,4,6-trinitrophenyl)-AMP
- TNP-ATP
- 2′,3′-O-(2,4,6-trinitrophenyl)-ATP
- TNP-GTP
- 2′,3′-O-(2,4,6-trinitrophenyl)-GTP
- EGTA
- ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′,-tetraacetic acid
- Received January 12, 1998.
- Accepted February 18, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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