Table 3. The effect of mutations within the SBP and extracellular loops of the D2R upon the pharmacology of SB269652.
Binding affinity and cooperativity values were obtained in competition or interaction binding experiments using the radioligand [3H]spiperone. Functional parameters for the interaction of SB269652 at WT and mutant D2R were determined in an assay measuring phosphorylation of ERK1/2. Values are expressed as mean ± S.D. from four separate experiments.
| Binding ([3H]spiperone) | Function (pERK1/2) | ||||
|---|---|---|---|---|---|
| pKB a (KB, nM) | Logαb (α) | Logα′c (α′) | pKB d (KB, nM) | Logαβe (αβ) | |
| WT | 6.11 ± 0.06 (776) | −0.54 ± 0.03 (0.28) | −0.54 ± 0.11 (0.28) | 6.26 ± 0.09 (550) | −1.23 ± 0.14 (0.06) |
| Y371.35A | 6.68 ± 0.18 (209) | −0.41 ± 0.04 (0.39) | −0.38 ± 0.12 (0.42) | 6.18 ± 0.14 (661) | −0.90 ± 0.02 (0.13) |
| L411.39A | 6.91 ± 0.17* (123) | −0.95 ± 0.08* (0.11) | - | 7.30 ± 0.19* (50) | −1.05 ± 0.06 (0.09) |
| V912.61A | - | - | - | 6.08 ± 0.08 (830) | −0.48 ± 0.16* (0.33) |
| E952.65A | 5.34 ± 0.22* (4570) | −0.21 ± 0.05* (0.62) | −0.33 ± 0.07 (0.47) | 5.14 ± 0.28* (7240) | −0.32 ± 0.14* (0.48) |
| L942.64A | 6.49 ± 0.04 (324) | −0.28 ± 0.06 (0.52) | - | 6.26 ± 0.20 (550) | −0.70 ± 0.08* (0.20) |
| G98ECL1A | 6.34 ± 0.08 (457) | −0.19 ± 0.11* (0.64) | - | 7.43 ± 0.14* (37) | −1.15 ± 0.07 (0.07) |
| K101ECL1A | 6.52 ± 0.04 (302) | −0.29 ± 0.07 (0.51) | - | 7.22 ± 0.10* (60) | −1.78 ± 0.06* (0.02) |
| F1103.28A | 6.74 ± 0.07 (182) | −0.30 ± 0.05 (0.50) | - | 6.31 ± 0.28 (490) | −0.38 ± 0.07* (0.42) |
| L174ECL2A | 6.45 ± 0.12 (354) | −0.40 ± 0.08 (0.40) | - | 6.57 ± 0.19 (269) | −1.04 ± 0.11 (0.09) |
| N180ECL2A | 5.99 ± 0.04 (1023) | −0.54 ± 0.10 (0.29) | - | 6.98 ± 0.14* (105) | −1.34 ± 0.09 (0.05) |
| E181ECL2A | 6.34 ± 0.24 (457) | −0.47 ± 0.10 (0.34) | −0.37 ± 0.03 (0.42) | 7.29 ± 0.13* (51) | −1.53 ± 0.12 (0.03) |
| I183ECL2A | 6.47 ± 0.24 (339) | −0.45 ± 0.05 (0.35) | - | 6.43 ± 0.18 (370) | −0.88 ± 0.08 (0.13) |
| I184ECL2A | 7.06 ± 0.14* (87) | −1.53 ± 0.03* (0.03) | −1.15 ± 0.13* (0.07) | 7.23 ± 0.08* (59) | −1.64 ± 0.08* (0.02) |
| A185ECL2S | 6.85 ± 0.24* (141) | −0.68 ± 0.08 (0.21) | - | 6.20 ± 0.12 (631) | −1.27 ± 0.08 (0.05) |
| N186ECL2A | 6.23 ± 0.13 (590) | −0.38 ± 0.06 (0.42) | - | 6.03 ± 0.17 (933) | −0.85 ± 0.09 (0.14) |
| S4097.36A | 6.03 ± 0.17 (933) | −0.77 ± 0.03 (0.17) | −0.87 ± 0.22 (0.13) | 6.03 ± 0.17 (933) | −1.08 ± 0.11 (0.08) |
| F4117.38A | 6.40 ± 0.10 (398) | −0.53 ± 0.06 (0.30) | - | 6.59 ± 0.10 (257) | −1.29 ± 0.07 (0.05) |
| T4127.39A | 7.25 ± 0.09* (56) | −1.04 ± 0.11* (0.09) | −0.93 ± 0.23 (0.12) | 7.20 ± 0.11* (63) | −1.55 ± 0.09 (0.02) |
Estimate of the negative logarithm of the equilibrium dissociation constant of SB269652
Logarithm of the affinity cooperativity factor between SB269652 and [3H]spiperone
Logarithm of the affinity cooperativity factor between SB269652 and dopamine
Estimate of the negative logarithm of the equilibrium dissociation constant of SB269652 eLogarithm of the net cooperativity factor between SB269652 and dopamine
P<0.05, significantly different from the wild-type receptor parameter determined by a one-way ANOVA, Dunnett post-hoc test