Binding affinities of peptide agonists and nonpeptide antagonists in the wild-type human NK1 receptor and in mutant forms with substitutions in TM-V
| hNK1 wild-type | [T201A] (V:09) | [T201I] (V:09) | [T201H] (V:09) | [T201H, I204H] (V:09, V:12) | |||||
|---|---|---|---|---|---|---|---|---|---|
| Ki | Ki | Fmut2-a | Ki | Fmut | Ki | Fmut | Ki | Fmut | |
| nm(n) | nm(n) | nm(n) | nm (n) | ||||||
| Substance P | 0.11 ± 0.04 (12) | 0.19 ± 0.03 (12) | 1.7 | 0.14 ± 0.03 (3) | 1.3 | 0.23 ± 0.05 (4) | 2.1 | 0.28 ± 0.02 (13) | 2.5 |
| SPOMe | 6.3 ± 1.4 (7) | 3.4 ± 0.2 (2) | 0.5 | 1.5 ± 0.1 (3) | 9.0 ± 1.2 (3) | 1.4 | 1.1 ± 0.3 (5) | 0.2 | |
| Ele | 21 ± 7 (9) | 8.3 ± 4.7 (3) | 0.4 | 9.3 ± 2.0 (3) | 0.4 | 44 ± 3 (3) | 2.1 | 5.4 ± 1.0 (5) | 0.3 |
| Neurokinin A | 14 ± 3 (9) | 6.8 ± 2.9 (3) | 0.5 | 4.6 ± 0.4 (3) | 0.3 | 23 ± 6 (3) | 1.6 | 3.9 ± 0.9 (5) | 0.3 |
| CP96,345 | 0.31 ± 0.05 (6) | 0.40 ± 0.04 (9) | 1.3 | 0.79 ± 0.16 (6) | 2.5 | 14 ± 3 (3) | 45 | 260 ± 60 (5) | 850 |
| CP99,994 | 0.28 ± 0.05 (9) | 0.49 ± 0.11 (3) | 1.8 | 0.36 ± 0.04 (3) | 1.3 | 3.2 ± 0.2 (3) | 11 | 21 ± 4 (4) | 75 |
| RP67,580 | 19 ± 4 (7) | 17 ± 3 (4) | 0.9 | 26 ± 2 (3) | 1.4 | 120 ± 10 (3) | 6.3 | 370 ± 70 (3) | 20 |
| RPR100,893 | 19 ± 3 (9) | 13 ± 3 (3) | 0.7 | 10 ± 1 (3) | 0.5 | 130 ± 10 (3) | 6.8 | 2000 ± 680 (8) | 110 |
| CAM4092 | 3.5 ± 0.8 (9) | 150 ± 40 (5) | 43 | 120 ± 10 (3) | 34 | 11 ± 1 (3) | 3.1 | 33 ± 7 (4) | 9.4 |
| CGP49,823 | 0.69 ± 0.13 (8) | 0.69 ± 0.31 (3) | 1.0 | 0.49 ± 0.07 (4) | 0.7 | 1.5 ± 0.5 (4) | 2.2 | 11 ± 1 (4) | 16 |
| LY303,870 | 0.38 ± 0.08 (7) | 26 ± 11 (4) | 68 | 4.6 ± 0.8 (3) | 12 | 3.9 ± 1.1 (4) | 10 | 3.8 ± 0.9 (4) | 10 |
| FK888 | 1.1 ± 0.1 (7) | 3.0 ± 1.4 (4) | 2.7 | 1.1 ± 0.3 (4) | 1.0 | 1.5 ± 0.3 (3) | 1.4 | 1.0 ± 0.4 (4) | 0.9 |
| SR140,333 | 0.44 ± 0.10 (7) | 0.40 ± 0.10 (5) | 0.9 | 0.33 ± 0.08 (3) | 0.8 | 0.93 ± 0.17 (3) | 2.1 | 4.2 ± 1.6 (4) | 9.5 |
Receptors were expressed transiently in COS-7 cells, and competition binding experiments were performed as described in the text using125I-BH-labeled substance P. B max values for the various constructs in fmol/105 cells were hNK1 wild-type, 15 ± 5; [T201A], 130 ± 22; [T201I], 30 ± 9; [T201H], 20 ± 8; and [T201H; I204H], 6.0 ± 1.1.
↵2-a Fmut is calculated as K i (mutant receptor)/K i (wild-type hNK1 receptor). This corresponds to fold decrease in affinity. Values are mean ± standard error.