Functional properties of recombinant heteromeric P2X receptors
| Heteromeric Receptor Type | ||||
|---|---|---|---|---|
| P2X2/3 | P2X4/6 | P2X1/5 | P2X2/6 | |
| Agonists EC50 (μM) | ||||
| ATP | 1 | 6 | 1 | 30 |
| 2MeSATP | 1 | 7 | 1 | 35 |
| αβmeATP | 1–3 | 12 | 3 | >100 |
| Antagonists IC50 (μM) | ||||
| Suramin | Block 30–100 μM | Block 10 μM | 1.6 μM | 6 |
| PPADS | Block 3–300 μM | Block 10 μM | 0.6 μM | |
| TNP-ATP | 0.007 μM | 0.4 μM | ||
| Brilliant Blue G | >10 μM | >10 μM | ||
| Ion effects | ||||
| Zn2+ | Potentiation EC50 6 μM | |||
| H+ | Potentiation at pH 6.3, block at pH 8.3 | Block at pH greater or less than pH 7.3 | Potentiation p Ka 7 Block pH 6.5–4 | |
| Ca2+ | Block IC50 15 mM | No effect on peak, but plateau is potentiated | ||
| Co-immunoprecipitation | Yes | Yes | Yes | Yes |
The P2X4/6 heteromer is blocked to a slightly greater degree by suramin and PPADS than homomeric P2X4 channels (Le et al., 1998a), but IC50 or affinity estimates are unknown. Data in the table are from the following references: Lewis et al., 1995;Radford et al., 1997; Le et al., 1998a, 1999; Thomas et al., 1998;Torres et al., 1998b, 1999; Virginio et al., 1998a,b; Haines et al., 1999; King et al., 2000; Surprenant et al., 2000.