Sequestration of hm2 and hm4 receptors coexpressed with GRKs in COS-7 cells
| hm2 receptors | hm4 receptors | |||
|---|---|---|---|---|
| Proportions of sequestered receptors | EC50 | Proportions of sequestered receptors | EC50 | |
| % | μm | % | μm | |
| Control | 48 ± 4 (7) | 2.1 | 45 ± 4 (3) | 9.0 |
| GRK2 | 58 ± 5 (6)1-a | 0.34 | 60 ± 5 (6)1-a | 1.6 |
| DN-GRK2 | 43 ± 6 (4) | 4.6 | 25 ± 3 (3)1-a | 16 |
| GRK4δ | 55 ± 3 (3) | 1.0 | 41 ± 6 (3) | 4.2 |
| GRK5 | 50 ± 2 (3) | 1.3 | 44 ± 5 (3) | 9.0 |
| GRK6 | 54 ± 3 (3) | 1.8 | 45 ± 7 (3) | 7.3 |
COS-7 cells expressing hm2 or hm4 receptors with or without GRKs were incubated with varying concentrations of carbamylcholine for 120 min. [3H]NMS binding was assayed as described in the text. Proportions of sequestered receptors were determined as decrease of [3H]NMS binding activity on cells treated with 10−4m carbamylcholine. Results are given as mean ± standard deviation from three to seven independent experiments. The number of experiments is indicated in parentheses. Dose-response curves for averaged values from three to seven independent experiments were fitted to the following equation: Rmax × EC50/(EC50 + [carbamylcholine]) + (100 − Rmax). EC50 values were determined as parameters.
↵1-a p < .01 compared with control cells.