Affinity and activity data for the wild-type and CB1 receptors with mutations at residue 268
Data are the median and corresponding 95% confidence limits or the mean ± S.E.M. of three independent experiments performed in duplicate. Bmax value for wild-type was 3825 ± 80 fmol/mg as reported in Table 1; Bmax value for F268Y was 3405 ± 228 fmol/mg. EC50 and Bmax values were determined from CP55940 dose-response model.
| Receptor | CP55940 | SR141716AKi | ||
|---|---|---|---|---|
| Ki | GTPγS | |||
| EC50 | Emax | |||
| nM | nM | %WT | nM | |
| Wild-type | 2.6 (1.5–4.6) | 2.80 (0.87–8.74) | 100.0 ± 5.2 | 5.2 (3.4–8.1) |
| F268Y | 2.3 (1.8–3.0) | 7.56 (2.48–23.1) | 83.1 ± 6.1 | 9.0 (7.9–10.3) |
| F268W | N.D.a | 481.5 (323.7–716.1)* | 21.8 ± 2.2* | 7.3 (6.4–8.3) |
| F268A | N.D.b | 226.6 (97.65–525.6)* | 10.2 ± 3.2* | N.D.c |
| F268N | N.D.d | 465.2 (260.0–832.5)* | 9.8 ± 2.7* | N.D.c |
N.D., no detectable binding up to 100 μM of displacing ligand at 20 nM tracer.
↵* Statistically significant differences from wild-type (p < 0.05) using analysis of variance followed by Dunn's post hoc test.
↵ a 26% displacement was observed at 32 μM CP55940 in presence of 20 nM [3H]CP55940.
↵ b 31% displacement was observed at 32 μM CP55940 in presence of 20 nM [3H]CP55940.
↵ d 28% displacement was observed at 32 μM CP55940 in presence of 20 nM [3H]CP55940.
↵ c No displacement was observed at 32 μM SR141716A in presence of 40 nM [3H]SR141716A.