TABLE 5.
Potency (pEC50), affinity (pKa), and coupling efficacy (log τ) values for (Ca2+)i mobilization at the CLR co-expressed with each RAMP stimulated with various agonists measured in HEK-293 and HEK-293S cells
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.
| HEK-293 |
HEK-293S |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| pEC50a | Emaxb | pKac | log τd | n | pEC50a | Emaxb | pKac | log τd | n | |
| RAMP1 | ||||||||||
| CGRP | 8.19 ± 0.1 | 79.68 ± 0.7 | 7.50 ± 0.1 | 0.60 ± 0.05 | 5 | 8.06 ± 0.1 | 67.64 ± 2.0 | 7.57 ± 0.1 | 0.32 ± 0.04 | 5 |
| AM | 7.90 ± 0.2 | 37.00 ± 3.5**** | 7.69 ± 0.4 | −0.24 ± 0.10 | 5 | 7.63 ± 0.2 | 38.18 ± 3.8**** | 7.42 ± 0.2 | −0.21 ± 0.07**** | 5 |
| AM2 | 6.76 ± 0.2*** | 25.05 ± 2.4**** | 6.64 ± 0.1** | −0.48 ± 0.06** | 5 | 6.94 ± 0.1*** | 33.28 ± 1.7**** | 6.76 ± 0.1** | −0.30 ± 0.03**** | 5 |
| RAMP2 | ||||||||||
| CGRP | 7.86 ± 0.1 | 63.20 ± 3.0 | 7.43 ± 0.1 | 0.54 ± 0.10 | 5 | 7.55 ± 0.3 | 55.35 ± 4.5 | 7.21 ± 0.3 | 0.07 ± 0.08 | 5 |
| AM | 7.86 ± 0.1 | 63.00 ± 1.8 | 7.45 ± 0.2 | −0.19 ± 0.06 | 5 | 7.68 ± 0.2 | 52.26 ± 4.5 | 7.39 ± 0.2 | 0.03 ± 0.10 | 5 |
| AM2 | 7.41 ± 0.4 | 44.41 ± 7.1* | 7.15 ± 0.4 | −0.10 ± 0.13** | 5 | 7.42 ± 0.4 | 20.17 ± 2.8**** | 7.33 ± 0.2 | −0.65 ± 0.13*** | 5 |
| RAMP3 | ||||||||||
| CGRP | 7.47 ± 0.2* | 84.39 ± 8.5* | 6.66 ± 0.4* | 0.74 ± 0.26 | 5 | 7.51 ± 0.2 | 65.3 ± 4.7 | 7.07 ± 0.2** | 0.24 ± 0.10* | 5 |
| AM | 8.12 ± 0.1 | 56.69 ± 6.6 | 7.76 ± 0.3 | 0.13 ± 0.13 | 5 | 8.02 ± 0.2 | 44.3 ± 3.2 | 8.56 ± 0.2 | −0.11 ± 0.06 | 5 |
| AM2 | 8.05 ± 0.3 | 19.99 ± 2.4* | 7.95 ± 0.3* | −0.63 ± 0.08* | 5 | 7.44 ± 0.3 | 20.1 ± 4.3 | 7.35 ± 0.3** | −0.62 ± 0.07** | 5 |
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 the maximal (Ca2+)i release as determined using 10 μm ionomycin stimulation.
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.