Synthesis and biological evaluation in vitro of selective, high affinity peptide antagonists of human melanin-concentrating hormone action at human melanin-concentrating hormone receptor 1.
Human melanin-concentrating hormone (hMCH) and many of its analogues are potent but nonspecific ligands for human melanin-concentrating hormone receptors 1 and 2 (hMCH-1R and hMCH-2R). To differentiate between the physiological functions of these receptors, selective antagonists are needed. In this study, analogues of Ac-Arg(6)-cyclo(S-S)(Cys(7)-Met(8)-Leu(9)-Gly(10)-Arg(11)-Val(12)-Tyr(13)-Arg(14)-Pro(15)-Cys(16))-NH(2), a high affinity but nonselective agonist at hMCH-1R and hMCH-2R, were prepared and tested in binding and functional assays on cells expressing these receptors. In the new analogues, 5-aminovaleric acid (Ava) was incorporated in place of the Leu(9)-Gly(10) and/or Arg(14)-Pro(15) segments of the disulfide ring. Several of these compounds turned out to be high affinity antagonists selective for hMCH-1R. Moreover, even at micromolar concentrations, they were devoid of agonist potency at both hMCH receptors and not effective as hMCH-2R antagonists. For example, peptide 14, Gva(6)- cyclo(S-S)(Cys(7)-Met(8)-Leu(9)-Gly(10)-Arg(11)-Val(12)-Tyr(13)-Ava(14,15)-Cys(16))-NH(2), (Gva = 5-guanidinovaleric acid), was a full competitive hMCH-1R antagonist (IC(50) = 14 nM, K(B) = 0.9 nM) with more than 1000-fold selectivity over hMCH-2R. Examination of various compounds with Ava in positions 9,10 and/or 14,15 revealed that the Leu(9)-Gly(10) and Arg(14)-Pro(15) segments of the disulfide ring are the principal structural elements determining hMCH-1R selectivity and ability to act as a hMCH-1R antagonist.
Bednarek
Maria A
MA
Department of Medicinal Chemistry, Merck Research Laboratories, R50G-141, Rahway, New Jersey 07065,USA. maria_bednarek@merck.com
Hreniuk
Donna L
DL
Tan
Carina
C
Palyha
Oksana C
OC
MacNeil
Douglas J
DJ
Van der Ploeg
Lex H Y
LH
Howard
Andrew D
AD
Feighner
Scott D
SD
D000331:Aequorin / Q000378:metabolism; D019943:Amino Acid Substitution; D021542:Amino Acids, Neutral / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D019556:COS Cells; D002460:Cell Line; D004220:Disulfides / Q000737:chemistry; D006801:Humans; D007028:Hypothalamic Hormones / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D008163:Luminescent Measurements; D008543:Melanins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000378:metabolism* / Q000494:pharmacology; D010907:Pituitary Hormones / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011869:Radioligand Assay; D043562:Receptors, G-Protein-Coupled; D011979:Receptors, Pituitary Hormone / Q000737:chemistry / Q000378:metabolism*; D014162:Transfection
D021542:Amino Acids, Neutral; D004220:Disulfides; D007028:Hypothalamic Hormones; D008024:Ligands; C431280:MCHR2 protein, human; D008543:Melanins; D010456:Peptides, Cyclic; D010907:Pituitary Hormones; D043562:Receptors, G-Protein-Coupled; D011979:Receptors, Pituitary Hormone; C092274:melanin-concentrating hormone receptor; D000331:Aequorin; C013809:5-aminovaleric acid; C019463:melanin-concentrating hormone