TABLE 2.
Summary of effect of chimeras and point mutations on a human P2X2 receptor background
Mean data are shown for peak current amplitude to a maximal concentration of ATP (usually 100 μm) as well as the time course for the peak current to decay by 50%. For mutants that did not decay by 50% during a 20-s application of a maximal concentration of ATP, the % of peak current remaining at 20 s is given. The decline in current amplitude on washout of ATP (deactivation) is expressed as the % of the current remaining at 50 s washout. ATP potency is given as pEC50 for some mutants. n = 3–20.
| Predominant P2X2 chimera/mutant | Peak current | pEC50 | In the presence of 100 μm ATP |
Washout of ATP % remaining at 50 s washout | |
|---|---|---|---|---|---|
| Desensitization to 50% peak | % remaining at 20 s | ||||
| μA | s | ||||
| P2X2 | 14.7 ± 2.2 | 4.9 ± 0.02 | 76.1 ± 5.39 | 0.3 ± 0.18 | |
| 1-N | 3.4 ± 0.5 | 4.8 ± 0.05 | 0.38 ± 0.15 | 8.8 ± 0.55a | 1.1 ± 0.97 |
| 1-Nα | 6.0 ± 1.5 | 93.0 ± 3.40b | 3.8 ± 0.50 | ||
| 1-Nβ | 1.2 ± 0.7 | 5.0 ± 0.05 | 0.38 ± 0.40 | 1.7 ± 0.67a | 1.3 ± 0.63 |
| 1-(E17D) | 11.3 ± 1.2 | 91.6 ± 2.58 | 0.8 ± 0.12 | ||
| 1-(20–23) | 3.8 ± 0.7 | 0.60 ± 0.05 | 0.8 ± 0.13a | 0.2 ± 0.06 | |
| 1-(21–23) | 9.3 ± 1.6 | 6.8 ± 0.90 | 21.2 ± 4.29a | 0.7 ± 0.66 | |
| 1-(27–29) | 17.0 ± 1.1 | 84.3 ± 2.47 | 8.0 ± 2.46c | ||
| 1-TM1 | 15.2 ± 1.6 | 77.0 ± 2.21 ns | 6.0 ± 1.73 | ||
| 1-ex | 4.5 ± 0.60 | 81.7 ± 3.43 | 26.2 ± 2.22a | ||
| 1-TM2 | 14.3 ± 1.6 | 95.0 ± 2.44a | 5.4 ± 2.72 | ||
| 1-TM1 and -2 | 20.0 ± 1.9 | 90.4 ± 2.08b | 4.2 ± 1.88 | ||
| 1-C | 6.4 ± 1.3 | 5.2 ± 0.04 | 86.6 ± 1.25 | 1.1 ± 0.70 | |
| 1-NC | 18.3 ± 1.2 | 7.2 ± 0.80 | 39.9 ± 5.42a | 4.0 ± 1.09 | |
| 1-(E17D) TM1 + 2 | 4.6 ± 0.9 | 9.6 ± 0.75 | 27.8 ± 2.28a | 0.005 ± 0.005 | |
| 1-(21–23) TM1 + 2 | 2.6 ± 0.5a | 0.1 ± 0.07 | 0 ± 0 | ||
| 1-TM1 + 2 Cα | 12.3 ± 0.9 | 87.8 ± 1.40 | 9.4 ± 2.33c | ||
a p < 0.001.
b p < 0.05.
c p < 0.01.