Table 1.
The ligand-binding and signaling properties of WT and mutant MC4Rs. Values are expressed as the mean ± standard error of the mean (S.E.M.) of at least three independent experiments. The maximal response (Rmax) of WT MC4R was 1662.19 ± 136.63 pmol cAMP/106 cells with NDP-MSH stimulation.
| NDP-MSH Binding | Basal Activity (% WT) | NDP-MSH-Stimulated cAMP | n | NDP-MSH-Stimulated ERK1/2 | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| n | IC50 (nM) | Bmax (% WT) | n | Basal cAMP levels | n | EC50 (nM) | Rmax (% WT) | |||
| WT | 14 | 19.43 ± 2.10 | 100 ± 0 | 31 | 100 ± 0 | 25 | 0.38 ± 0.07 | 100 ± 0 | 16 | + |
| D146A | 3 | 3.24 ± 0.70 a | 6.47 ± 0.97 b | 9 | 292.67 ± 35.94 b | 4 | 1.07 ± 0.18 a | 108.52 ± 12.25 | 6 | – |
| R147A | 3 | 11.86 ± 0.25 | 176.71 ± 38.93 | 4 | 23.62 ± 4.31 b | 4 | 1.73 ± 0.44 a | 121.75 ± 14.65 | 6 | – |
| Y148A | 3 | 4.31 ± 1.78 b | 60.38 ± 10.62 a | 9 | 126.90 ± 9.86 a | 3 | 0.21 ± 0.09 | 136.92 ± 8.17 a | 6 | – |
| F149A | 3 | 6.30 ± 0.83 | 156.37 ± 13.73 a | 8 | 233.51 ± 26.15 a | 3 | 0.24 ± 0.08 | 154.21 ± 31.84 | 5 | – |
| T150A | 3 | 40.25 ± 6.11 a | 95.30 ± 3.43 | 4 | 19.34 ± 4.05 b | 4 | 11.55 ± 2.38 b | 17.62 ± 3.60 b | 6 | + |
| I151A | 4 | 17.78 ± 6.96 | 124.47 ± 28.35 | 3 | 38.42 ± 15.77 a | 3 | 3.29 ± 0.27 b | 93.52 ± 24.82 | 5 | + |
| F152A | 3 | 17.29 ± 5.63 | 76.21 ± 14.64 | 11 | 228.74 ± 33.95 b | 5 | 0.06 ± 0.02 a | 115.47 ± 14.57 | 5 | + |
| Y153A | 3 | 13.02 ± 5.03 | 56.84 ± 4.52 b | 9 | 194.08 ± 31.05 b | 3 | 0.26 ± 0.10 | 152.24 ± 28.47 | 5 | – |
| A154G | 3 | 28.72 ± 9.72 | 84.83 ± 6.18 | 3 | 80.70 ± 21.17 | 3 | 0.87 ± 0.10 | 110.06 ± 10.78 | 8 | + |
| L155A | 3 | 50.80 ± 14.05 | 79.61 ± 8.63 | 4 | 21.77 ± 5.64 b | 4 | 6.03 ± 1.42 b | 100.44 ± 5.25 | 7 | + |
| Q156A | 3 | 15.41 ± 5.45 | 61.26 ± 6.10 b | 4 | 133.59 ± 27.19 | 4 | 1.76 ± 0.43 a | 129.25 ± 23.87 | 8 | + |
| Y157A | 3 | 7.43 ± 2.02 | 14.88 ± 2.18 b | 5 | 24.72 ± 2.89 b | 4 | 2.85 ± 0.61 b | 131.64 ± 18.30 | 7 | – |
| H158A | 3 | 10.36 ± 3.15 | 138.97 ± 25.34 | 8 | 761.86 ± 111.54 b | 3 | 0.03 ± 0.02 a | 109.75 ± 26.84 | 7 | – |
| N159A | 3 | 15.19 ± 5.31 | 119.92 ± 6.62 a | 4 | 79.16 ± 16.55 | 4 | 0.30 ± 0.07 | 92.29 ± 16.32 | 7 | + |
| I160A | 3 | 6.77 ± 2.07 a | 95.24 ± 16.43 | 3 | 88.84 ± 15.64 | 3 | 0.20 ± 0.18 | 109.91 ± 28.73 | 7 | – |
| M161A | 4 | 3.47 ± 1.19 b | 13.18 ± 2.67 b | 4 | 72.38 ± 9.95 | 4 | 0.41 ± 0.16 | 137.22 ± 11.70 a | 7 | – |
| T162A | 3 | 5.79 ± 2.35 | 13.73 ± 1.17 b | 4 | 60.37 ± 13.41 | 4 | 0.46 ± 0.10 | 145.81 ± 13.95 a | 8 | + |
a significantly different from WT, p < 0.05; b significantly different from WT, p < 0.001.