TABLE 1

Maximal current responses (Imax) and half-maximal agonist concentrations (EC50) of nucleotides at the wt P2X3 receptor and its K65A mutant expressed in HEK293 cells

Experimental concentration-response curves were determined with the whole-cell patch-clamp method. Simulated concentration-response curves were generated by means of a hidden Markov model (see Materials and Methods and Fig. 2C). A comparison of the experimental and simulated curves is shown in Supplemental Figure 1.

Receptor and AgonistExperimentalSimulation
ImaxEC50Hill CoefficientnEC50Hill Coefficient
pAμMμM
wt
    ATP5235 ± 11302.5 ± 1.80.85 ± 0.16143.8 ± 0.10.91 ± 0.01
    α,β-me-ATP5218 ± 3898.7 ± 2.71.26 ± 0.09137.1 ± 0.20.96 ± 0.02
    2-MeS-ATP1831 ± 111*1.5 ± 0.31.20 ± 0.0870.74 ± 0.010.93 ± 0.01
    dATP6132 ± 76210.5 ± 2.71.64 ± 0.18*1126.0 ± 0.90.97 ± 0.18
    ATP-γ-S4938 ± 37126.0 ± 6.11.15 ± 0.15513.7 ± 0.51.03 ± 0.03
    β,γ-me-ATP2828 ± 2846.2 ± 0.93.77 ± 0.52*729.1 ± 1.01.15 ± 0.01
    Bz-ATP608 ± 43*2.6 ± 0.61.67 ± 0.444
    GTP1467 ± 789*171.8 ± 152.31.17 ± 0.168243.7 ± 23.31.15 ± 0.04
    CTP8876 ± 5605119.5 ± 177.51.18 ± 0.251332.6 ± 1.21.03 ± 0.02
K65A
    ATP6087 ± 110216.9 ± 8.0†1.41 ± 0.16†715.9 ± 0.41.01 ± 0.02
    α,β-me-ATP1332 ± 8*†69.3 ± 0.8*†1.71 ± 0.02*†562.5 ± 3.21.08 ± 0.04
    2-MeS-ATP12,407 ± 447372.2 ± 83.00.76 ± 0.27841.0 ± 1.31.12 ± 0.03
    dATP2934 ± 17*†247.8 ± 2.2*†2.47 ± 0.05*†4810.4 ± 8.31.70 ± 0.01
    ATP-γ-S5066 ± 10676.6 ± 2.9*†1.86 ± 0.09*†4442.3 ± 15.31.27 ± 0.02
    β,γ-me-ATP2533 ± 25*†371.5 ± 5.5*†2.27 ± 0.06*42.1 ± 73.11.75 ± 0.01
    CTP7357 ± 15157.7 ± 0.7*1.99 ± 0.01*4597.5 ± 5.91.67 ± 0.01
    GTP2694 ± 68.21188.3 ± 45.51.92 ± 0.0943299 ± 42.31.75 ± 0.01

  • ↵* P < 0.05, statistically significant difference from the respective value with ATP as an agonist.

  • ↵† P < 0.05, statistically significant difference from the respective value with the wt P2X3 receptor.