Table 5.
Effects of GLP-1R mutation on signal pathway bias. Data were analysed using an operational model of agonism to estimate log τc/KA ratios. Changes in log τc/KA ratios with respect to WT were calculated to provide a measure of the degree of stimulus bias exhibited by mutant receptors across the three pathways relative to that of the control receptor (WT). Values are expressed as mean ± S.E.M of four to six independent experiments, conducted in duplicate. Data were analysed with one-way analysis of variance and Dunnett’s post test (*p < 0.05). ND indicates data unable to be experimentally defined.
| Δlog Rn relative to WT |
|||||||||
|---|---|---|---|---|---|---|---|---|---|
| pERK1/2-cAMP |
ERK-iCa2+ |
iCa2+-cAMP |
|||||||
| GLP-1 | Oxyntomodulin | Exendin-4 | GLP-1 | Oxyntomodulin | Exendin-4 | GLP-1 | Oxyntomodulin | Exendin-4 | |
| Wildtype | 0.00 ± 0.12 (1.0) | 0.00 ± 0.07 (1.0) | 0.00 ± 0.09 (1.0) | 0.00 ± 0.11 (1.0) | 0.00 ± 0.10 (1.0) | 0.00 ± 0.10 (1.0) | 0.00 ± 0.13 (1.0) | 0.00 ± 0.15 (1.0) | 0.00 ± 0.09 (1.0) |
| R2.46176A | 0.29 ± 0.15 (1.9) | 0.70 ± 0.15 (5.0) | 0.37 ± 0.16 (2.3) | 0.29 ± 0.29 (1.9) | −0.24 ± 0.33 (0.57) | 0.57 ± 0.31 (3.7) | 0.57 ± 0.32 (3.7) | 0.52 ± 0.33 (3.3) | −0.21 ± 0.31 (0.62) |
| N2.52182A | 0.31 ± 0.32 (2.0) | 0.86 ± 0.21 (7.2) | 0.99 ± 0.20 (9.8)∗ | ND | ND | ND | ND | ND | ND |
| R3.30227A | 0.52 ± 0.24 (3.3) | 0.97 ± 0.12 (9.3) | 0.25 ± 0.17 (1.8) | 0.26 ± 0.17 (1.8) | −1.06 ± 0.15 (0.09)∗ | 0.24 ± 0.18 (1.7) | 0.86 ± 0.26 (7.2)∗ | 0.81 ± 0.17 (6.4) | 0.52 ± 0.14 (3.3) |
| Y3.53250A | −0.94 ± 0.39 (0.11) | −1.13 ± 0.36 (0.07)∗ | −0.44 ± 0.30 (0.36) | ND | ND | ND | ND | ND | ND |
| K4.64288A | 0.69 ± 0.32 (4.9) | 0.68 ± 0.37 (4.8) | 1.17 ± 0.12 (15)∗ | ND | −0.80 ± 0.28 (0.16) | ND | ND | 1.17 ± 0.32 (15)∗ | ND |
| R5.40310A | 1.04 ± 0.41 (11) | 0.65 ± 0.33 (4.5) | 0.96 ± 0.49 (9.1) | ND | ND | ND | ND | ND | ND |
| R5.56326A | −1.03 ± 0.23 (0.09)∗ | 0.49 ± 0.16 (3.1) | −0.02 ± 0.17 (0.95) | −0.19 ± 0.35 (0.64) | ND | 0.67 ± 0.57 (4.7) | −0.83 ± 0.18 (0.15)∗ | ND | −0.50 ± 0.35 (0.32) |
| K6.35346A | −0.51 ± 0.26 (0.31) | −0.65 ± 0.26 (0.22) | −0.38 ± 0.11 (0.42) | −0.56 ± 0.23 (0.34) | 0.08 ± 0.24 (1.2) | −0.82 ± 0.07 (0.15) | −0.66 ± 0.13 (0.22) | −1.54 ± 0.11 (0.03)∗ | 0.37 ± 0.10 (2.3) |
| R6.37348A | −0.16 ± 0.16 (0.69) | 0.49 ± 0.13 (3.1) | 0.49 ± 0.14 (3.1) | 1.38 ± 0.36 (24)∗ | 0.61 ± 0.24 (4.1) | 0.84 ± 0.09 (6.9) | −1.40 ± 0.25 (0.04)∗ | −0.11 ± 0.23 (0.79) | −0.25 ± 0.29 (0.56) |
| K6.40351A | −0.19 ± 0.21 (0.65) | −1.18 ± 0.28 (0.07)∗ | −0.51 ± 0.24 (0.30) | ND | −1.07 ± 0.18 (0.09)∗ | 0.10 ± 0.24 (1.3) | ND | −0.24 ± 0.29 (0.57) | −1.08 ± 0.21 (0.08)∗ |
| E7.63408A | 0.80 ± 0.27 (6.3) | 0.36 ± 0.21 (2.3) | 0.64 ± 0.22 (4.4) | 0.15 ± 0.33 (1.4) | −0.54 ± 0.27 (0.29) | −0.30 ± 0.29 (0.50) | 0.90 ± 0.15 (8.0)∗ | 0.70 ± 0.24 (5.0) | 0.88 ± 0.29 (7.7) |
| Q7.65410A | −0.37 ± 0.10 (0.43) | −0.48 ± 0.44 (0.33) | −0.10 ± 0.25 (0.79) | ND | −1.07 ± 0.48 (0.08)∗ | 0.90 ± 0.54 (7.9) | ND | 0.47 ± 0.18 (3.0) | −1.24 ± 0.52 (0.06)∗ |