Discovery and in vivo evaluation of new melanocortin-4 receptor-selective peptides.
The melanocortin-4 receptor (MC4R) is involved in several physiological processes, including body weight regulation and grooming behaviour in rats. It has also been suggested that the MC4R mediates the effects of melanocortin ligands on neuropathic pain. Selective compounds are needed to study the exact role of the MC4R in these different processes. We describe here the development and evaluation of new melanocortin compounds that are selective for the MC4R as compared with the other centrally expressed receptors, MC3R and MC5R. First, a library of 18 peptides, in which a melanocortin-based sequence was systematically point-mutated, was screened for binding to and activity on the MC3R, MC4R and MC5R. Compound Ac-Nle-Gly-Lys-D-Phe-Arg-Trp-Gly-NH(2) (JK1) appeared to be the most selective MC4R compound, based on affinity. This compound is 90- and 110-fold selective for the MC4R as compared to the MC3R and MC5R, respectively. Subsequent modification of JK1 yielded compound Ac-Nle-Gly-Lys-D-Nal(2)-Arg-Trp-Gly-NH(2) (JK7)(,) a selective MC4R antagonist with 34-fold MC4R/MC3R and 109-fold MC4R/MC5R selectivity. The compounds were active in vivo as determined in a grooming assay and a model for neuropathic pain in rats. Intravenous (i.v.) injections suggested that they were able to pass the blood-brain barrier.The compounds identified here will be useful in further research on the physiological roles of the MC4R.
Nijenhuis
Wouter A J
WA
Department of Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG, Utrecht, The Netherlands.
Kruijtzer
John A W
JA
Wanders
Nienke
N
Vrinten
Dorien H
DH
Garner
Keith M
KM
Schaaper
Wim M M
WM
Meloen
Rob H
RH
Gispen
Willem Hendrik
WH
Liskamp
Rob M
RM
Adan
Roger A H
RA
D019943:Amino Acid Substitution; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001665:Binding Sites; D001667:Binding, Competitive; D002460:Cell Line; D045744:Cell Line, Tumor; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D006120:Grooming / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D008297:Male; D009842:Oligopeptides / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D010147:Pain Measurement / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D044105:Receptor, Melanocortin, Type 4 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D044101:Receptors, Melanocortin / Q000037:antagonists & inhibitors / Q000378:metabolism; D013997:Time Factors; D000521:alpha-MSH / Q000378:metabolism / Q000494:pharmacology
D009842:Oligopeptides; D044105:Receptor, Melanocortin, Type 4; D044101:Receptors, Melanocortin; D000521:alpha-MSH