Pharmacological parameters for wild-type and glycosylated mutant GRP-R transiently expressed by CHOP cells and stably expressed by Balb 3T3 cells
| Mutant | CHOP Cells | Balb 3T3 Cells | |||||
|---|---|---|---|---|---|---|---|
| Binding | [3H]IP | ||||||
| Ki | Bmax | Molecular Mass | Ki | Bmax | EC50 | Fold Increase | |
| nM | fmol/106cells | kDa | nM | fmol/106 cells | nM | ||
| Wild type | 3.6 ± 0.8 | 78 ± 12 | 83 ± 1 | 2.4 ± 0.4 | 523 ± 31 | 2.9 ± 0.9 | 6.1 |
| N5Q | 2.8 ± 0.2 | 74 ± 12 | 70 ± 1 | 5.3 ± 1.5 | 620 ± 22 | 4.9 ± 0.8 | 4.5 |
| N20Q | 3.4 ± 0.3 | 68 ± 9 | 73 ± 1 | 2.9 ± 0.7 | 433 ± 65 | 3.8 ± 0.5 | 6.0 |
| N24Q | 2.9 ± 0.1 | 2.6 ± 0.1 | 78 ± 1 | 4.2 ± 1.1 | 457 ± 61 | 5.3 ± 1.1 | 6.2 |
| N5,20,24Q | N.D. | N.D. | 52 ± 1 | 3.9 ± 1.9 | 592 ± 47 | 5.1 ± 0.9 | 4.6 |
Data are expressed as the mean ± S.E. of at least three separate experiments. Receptor affinity (K i) and number (B max) were calculated using the least squares curve-fitting program LIGAND. For CHOP cells, 5 μg of cDNA was used for CaPO4 precipitation as described under Experimental Procedures, and binding parameters were determined using the bombesin receptor-specific antagonist125I-[d-Tyr6]bombesin methyl ester. Data are mean ± 1 S.E.M. of at least three separate experiments.
EC50, concentration necessary for half-maximal increases in [3H]IP; N.D., not determinable.