Table 1.
Binding, signalling, and internalisation parameter estimates for the ligands in this study. Signalling parameter measures were determined as follows: an initial 4-parameter fit was constructed for all full agonists, with globally constrained basal response Emax and Hill slope, to establish the maximal response for the assay (note that for β-arrestin-2 measurement, D3-exendin-4 was the only full agonist). Individual responses were normalised to the assay maximum and parameter estimates for each assay recalculated by 4-parameter fitting with globally constrained basal response and Hill slope, but no constraint to Emax. For internalisation, curve fitting was performed similarly but without prior normalisation to a maximal response. Note that for β-arrestin-2, meaningful estimates of [F1,G40,K41.C16 diacid]exendin-4 could not be calculated (n.c.), as was also the case for both F1-exendin-4 and [F1,G40,K41.C16 diacid]exendin-4 for internalisation. Average ± SEM values are reported.
| CHO–K1-βarr2-EA-GLP-1R |
INS-1 832/3 |
MIN6B1 |
HEK293-SNAP-GLP-1R |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| cAMP |
βarr2 |
cAMP |
cAMP |
cAMP (1% FBS) |
Internalisation |
Binding |
|||||||
| pEC50 (M) | Emax (% max) | pEC50 (M) | Emax (% max) | pEC50 (M) | Emax (% max) | pEC50 (M) | Emax (% max) | pEC50 (M) | Emax (% max) | pEC50 (M) | Emax (AUC) | pKd (M) | |
| D3-exendin-4 | 9.3 ± 0.0 | 96 ± 4 | 7.8 ± 0.1 | 100 | 9.0 ± 0.3 | 100 ± 2 | 11.0 ± 0.3 | 101 ± 2 | 10.6 ± 0.3 | 96 ± 2 | 7.8 ± 0.1 | 38 ± 4 | 9.1 ± 0.1 |
| [D3,K40.C16 diacid]exendin-4 | 9.1 ± 0.1 | 100 ± 4 | 7.6 ± 0.2 | 81 ± 2 | 8.7 ± 0.2 | 101 ± 2 | 10.8 ± 0.2 | 97 ± 1 | 10.4 ± 0.2 | 97 ± 3 | 8.3 ± 0.2 | 35 ± 4 | 8.9 ± 0.1 |
| F1-exendin-4 | 8.8 ± 0.1 | 97 ± 2 | 7.3 ± 0.1 | 14 ± 1 | 8.4 ± 0.3 | 97 ± 3 | 9.2 ± 0.4 | 97 ± 5 | 9.0 ± 0.1 | 83 ± 1 | n.c. | n.c | 7.8 ± 0.0 |
| [F1,K40.C16 diacid]exendin-4 | 8.0 ± 0.1 | 107 ± 3 | n.c. | n.c | 7.5 ± 0.2 | 41 ± 4 | 7.9 ± 0.3 | 98 ± 7 | 8.2 ± 0.1 | 49 ± 3 | n.c. | n.c | 8.3 ± 0.0 |