Table 1.
Binding and signaling characteristics of κ-WT and prototype RASSLs
| Assay | Ligand | Receptor
|
|||
|---|---|---|---|---|---|
| κ-WT | Ro1 | E/Q | Ro2 | ||
| Binding (competition), Ki | DynA(1–13) | 0.06 ± 0.04 | 14.64 ± 2.99 (229) | 0.36 ± 0.11 (5.6) | 124.52 ± 19.38 (1946) |
| Bremazocine | 0.04 ± 0.01 | 0.06 ± 0.03 (1.7) | 0.04 ± 0.02 (0.92) | 0.05 ± 0.02 (1.2) | |
| Spiradoline | 1.32 ± 0.38 | 6.29 ± 1.92 (4.8) | 1.09 ± 0.23 (0.83) | 5.65 ± 1.19 (4.3) | |
| ICI 204,448 | 4.02 ± 2.01 | 30.70 ± 6.76 (7.6) | 3.51 ± 1.10 (0.87) | 12.51 ± 4.90 (3.1) | |
| Binding (saturation), Kd | EKC | 0.17 ± 0.09 | 0.25 ± 0.11 (0.88) | 0.15 ± 0.05 (1.5) | 0.20 ± 0.044 (1.2) |
| Adenylyl cyclase, EC50 | DynA(1–13) | 0.66 ± 0.62 | 61.03 ± 20.56 (92.8) | 1.35 ± 1.4 (2.1) | 1083.73 ± 367 (1649) |
| Bremazocine | 0.07 ± 0.05 | 0.07 ± 0.039 (1.0) | 0.05 ± 0.02 (0.74) | 0.34 ± 0.21 (5.2) | |
| [3H]Thymidine, EC50 | DynA(1–13) | 8.53 ± 4.85 | >1000 (>117) | ||
| Spiradoline | 4.39 ± 3.0 | 5.49 ± 2.81 (1.3) | |||
Data are expressed in nanomolars as mean ± SD. Fold differences from κ-WT are shown in parentheses. For the ligand-binding experiments, each Ki value was derived from four independent experiments, and the Kd values were derived from two independent experiments performed in duplicate. For the adenylyl cyclase inhibition assay, the EC50 values were determined from five (dynorphin) or two (bremazocine) experiments performed in triplicate. Maximal inhibition of adenylyl cyclase was approximately 60% for each receptor. For the [3H]thymidine incorporation assay, EC50 values were determined from three separate experiments performed in duplicate.