Table 2.
Binding Affinities and cAMP Activities of Cyclic α-MSH Analogues at hMCRsa
| hMC1R
|
hMC3R
|
hMC4R
|
hMC5R
|
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. | sequence | IC50, nM | EC50, nM | % max effect | IC50, nM | EC50, nM | % max effect | IC50, nM | EC50, nM | % max effect | IC50, nM | EC50, nM | % max |
| MT-II | Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 | 0.2 ± 0.01 | 0.3 ± 0.04 | 100 | 1.25 ± 0.2 | 1.85 ± 0.2 | 100 | 1.07 ± 0.3 | 2.87 ± 0.52 | 100 | 7.47 ± 0.23 | 3.3 ± 0.7 | 100 |
| 4 | c[CO-o-C6H4-CO-Pro-D-Phe-Arg-Trp-Lys]-NH2 | >10000 | NA | 0 | >1000 | 95 ± 11 | 100 | 777 ± 200 | NA | 0 | >1000 | NA | 0 |
| 5 | c[CO-o-C6H4-CO-Pro-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 410 ± 80 | >5000 | 80 | 32 ± 4 | NA | 0 | 430 ± 100 | NA | 0 | 210 ± 30 | NA | 0 |
| 6 | c[CO-(CH2)3-CO-Pro-D-Phe-Arg-Trp-Lys]-NH2 | >10000 | NA | 0 | 385 ± 50 | 29 ± 3 | 100 | >1000 | >2000 | 12 | 870 ± 100 | 570 ± 60 | 40 |
| 7 | c[CO-(CH2)3-CO-Pro-D-Nal(2′)-Arg-Trp-Lys]-NH2 | >10000 | NA | 0 | 11 ± 2 pA2 = 9.8 | NA | 0 | 330 ± 40 | NA | 0 | 27 ± 3 | 23 ± 7 | 40 |
| 8 | c[CO-cis-CH=CH-CO-Pro-D-Phe-Arg-Trp-Lys]-NH2 | >10000 | NA | 0 | >1000 | 100 ± 20 | 80 | 160 ± 20 | NA | 0 | 790 ± 100 | NA | 0 |
| 9 | c[CO-cis-CH=CH-CO-Pro-D-Nal(2′)-Arg-Trp-Lys]-NH2 | >10000 | NA | 0 | 20 ± 3 | NA | 0 | 520 ± 60 | NA | 0 | 120 ± 20 | NA | 0 |
| 10 | c[CO-2,6-pyridine-CO-D-Phe-Arg-Trp-Lys]-NH2 | >10000 | >1000 | 15 | >10000 | NA | 0 | >10000 | NA | 0 | >10000 | NA | 0 |
| 11 | c[CO-2,6-pyridine-CO-D-Nal(2′)-Arg-Trp-Lys]-NH2 | >10000 | NA | 0 | >1000 | NA | 0 | >1000 | NA | 0 | >10000 | NA | 0 |
| 12 | c[CO-2,3-pyrazine-CO-D-Phe-Arg-Trp-Lys]-NH2 | 412 ± 50 | >10000 | 60 | 1100 ± 120 | 27 ± 3 | 70 | >10000 | NA | 0 | >10000 | NA | 0 |
| 13 | c[CO-2,3-pyrazine-CO-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 707 ± 101 | >3000 | 55 | 23 ± 5 | NA | 0 | >1000 | NA | 0 | 230 ± 40 | NA | 0 |
| 14 | c[CO-(CH2)2-CO-Nle-D-Phe-Arg-Trp-Lys]-NH2 | >10000 | NA | 0 | 84 ± 10 | NA | 0 | 930 ± 133 | NA | 0 | 520 ± 70 | >1000 | 40 |
| 15 | c[CO-(CH2)2-CO-Nle-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 2000 ± 200 | >1000 | 20 | 12 ± 3 pA2 = 8.3 | NA | 0 | 300 ± 100 | NA | 0 | 17 ± 2 pA2 = 8.7 | NA | 0 |
a
IC50 = concentration of peptide at 50% specific binding (N = 4). EC50 = effective concentration of peptide that was able to generate 50% maximal intracellular cAMP accumulation (N = 4). % max effect = % of cAMP produced at 10 μM ligand concentration, in relation to MT-II. NA = 0% cAMP accumulation observed at 10 μM. The peptides were tested at a range of concentration from 10−10 to 10−5 M.