TABLE 1.
Summary of pharmacological parameters for various ligands upon expression of the CLR with each RAMP in yeast strains containing GPA1/Gαs, GPA1/Gαi, or the GPA1/Gαq chimera
Data are the mean ± S.E. of n individual data sets. Statistical significance compared with the cognate ligand (*, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001) for each receptor heterodimer (CGRP for RAMP1 + CLR and AM for CLR with either RAMP2 or RAMP3) was determined by one-way ANOVA with Dunnett's post-test.
| RAMP1-CLR |
RAMP2-CLR |
RAMP3-CLR |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| CGRP | AM | AM2 | CGRP | AM | AM2 | CGRP | AM | AM2 | |
| GPA1/Gαs | |||||||||
| pEC50a | 9.35 ± 0.2* | 8.80 ± 0.4*** | 7.22 ± 0.3*** | 7.60 ± 0.3* | 8.82 ± 0.3* | 8.05 ± 0.3* | 8.24 ± 0.2 | 8.15 ± 0.4 | 8.85 ± 0.3 |
| Emaxb | 27.10 ± 1.6* | 20.39 ± 2.8*** | 20.65 ± 1.1*** | 30.34 ± 4.1 | 37.46 ± 3.5 | 19.90 ± 2.5*** | 30.17 ± 2.7 | 25.51 ± 3.6 | 22.80 ± 2.3 |
| pKac | 9.22 ± 0.2* | 8.81 ± 0.3*** | 7.31 ± 0.3*** | 7.70 ± 0.3* | 8.77 ± 0.3 | 8.10 ± 0.3 | 8.30 ± 0.3 | 8.10 ± 0.3 | 8.61 ± 0.4 |
| log τd | −0.43 ± 0.04 | −0.59 ± 0.07* | −0.61 ± 0.08 | −0.38 ± 0.08* | −0.23 ± 0.06 | −0.61 ± 0.06** | −0.42 ± 0.08 | −0.51 ± 0.08 | −0.57 ± 0.08 |
| n | 6 | 6 | 6 | 7 | 7 | 7 | 8 | 8 | 8 |
| GPA1/Gαi | |||||||||
| pEC50a | 8.26 ± 0.5 | 8.38 ± 0.3 * | 8.57 ± 0.2** | 8.89 ± 0.2** | 7.91 ± 0.2** | 8.42 ± 0.5** | 8.52 ± 0.2 | 7.89 ± 0.8 | 8.49 ± 0.2 |
| Emaxb | 19.80 ± 3.0* | 34.20 ± 3.7*** | 41.5 ± 3.3**** | 24.43 ± 1.7* | 24.49 ± 2.0* | 15.71 ± 2.5* | 22.60 ± 1.8* | 26.71 ± 1.8* | 15.71 ± 2.1* |
| pKac | 8.40 ± 0.5 | 8.20 ± 0.3** | 8.24 ± 0.2 | 8.64 ± 0.2 | 7.75 ± 0.2 | 8.30 ± 0.5 | 8.37 ± 0.2 | 8.00 ± 0.2 | 8.30 ± 0.3 |
| log τd | −0.70 ± 0.1** | −0.33 ± 0.07** | −0.18 ± 0.1*** | −0.50 ± 0.04** | −0.51 ± 0.05* | −0.89 ± 0.1** | −0.56 ± 0.06* | −0.50 ± 0.05* | −0.78 ± 0.07* |
| n | 6 | 6 | 6 | 6 | 6 | 6 | 7 | 7 | 7 |
| GPA1/Gαq | |||||||||
| pEC50a | 7.53 ± 0.1 | 7.26 ± 0.2 | 7.99 ± 0.2 | 7.14 ± 0.2 | 7.93 ± 0.2 | 9.22 ± 0.4* | 6.19 ± 0.5* | 7.83 ± 0.2 | 6.76 ± 0.25 |
| Emaxb | 26.50 ± 1.2 | 14.08 ± 1.2**** | 16.73 ± 1.1**** | 27.74 ± 2.3 | 29.03 ± 2.6 | 11.33 ± 1.3**** | 20.7 ± 4.2 | 25.56 ± 2.0 | 32.11 ± 3.7 |
| pKac | 27.40 ± 0.1 | 7.19 ± 0.2 | 7.91 ± 0.03 | 7.01 ± 0.2 | 7.78 ± 0.2 | 9.16 ± 0.4* | 6.10 ± 0.6* | 7.71 ± 0.2 | 6.60 ± 0.3 |
| log τd | −0.46 ± 0.03 | −0.79 ± 0.04*** | −0.70 ± 0.04*** | −0.42 ± 0.05 | −0.39 ± 0.05 | −0.88 ± 0.08*** | −0.63 ± 0.2 | −0.48 ± 0.05 | −0.34 ± 0.1 |
| n | 7 | 7 | 7 | 6 | 6 | 6 | 6 | 6 | 6 |
a The negative logarithm of the agonist concentration required to produce a half-maximal response.
b The maximal response to the ligand expressed as a percentage of that obtained from a yeast strain (MMY11) lacking GPA1.
c The negative logarithm of the equilibrium disassociation constant for each ligand generated through use of the operational model of agonism (34).
d Log τ is the coupling efficacy parameter of each ligand.