title: Novel cyclic templates of alpha-MSH give highly selective and potent antagonists/agonists for human melanocortin-3/4 receptors.
abstract: In an effort to develop highly selective and potent agonists and/or antagonists for the hMC3 and hMC4 receptors, a new approach involving the use of linker arms and a backbone to side chain cyclization strategy was employed. Three key analogues were identified to have the required selectivity and potency at the hMC3 or hMC4 receptors, implicated to play pivotal roles in energy homeostasis and other biological effects. The novel cyclic peptide (O)C-CH(2)-CH(2)-C(O)-c-[His(6)-D-Phe(7)-Arg(8)-Trp(9)-Lys(10)]-NH(2) (1) was found to be a highly selective and potent agonist of the hMC4 receptor. Structure-activity studies have shown that replacing the succinyl linker arm of 1 by an o-phthalic acid group and substituting a D-Nal(2')(7) residue in place of D-Phe(7) results in a potent antagonist 7 at the hMC4 receptor. Furthermore, increasing the 23-membered lactam ring of 1 by one carbon atom (succinyl --> glutaric acid linker) gives a highly selective and potent antagonist 9 for the hMC3 receptor. Analogues 1, 7, and 9 therefore represent the first examples of a class of cyclic melanotropin ligands with high selectivity and defined biological activities at the physiologically important hMC3 and hMC4 receptors.
authors.affiliation: Department of Chemistry, College of Science, University of Arizona, 1306 East University, Tucson, AZ 85721, USA.
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: Kavarana
authors.forename: Dev
authors.initials: D
authors.lastname: Trivedi
authors.forename: Minying
authors.initials: M
authors.lastname: Cai
authors.forename: Jinfa
authors.initials: J
authors.lastname: Ying
authors.forename: Matthew
authors.initials: M
authors.lastname: Hammer
authors.forename: Christopher
authors.initials: C
authors.lastname: Cabello
authors.forename: Paolo
authors.initials: P
authors.lastname: Grieco
authors.forename: Guoxia
authors.initials: G
authors.lastname: Han
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Hruby
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D001667:Binding, Competitive; D002460:Cell Line; D006801:Humans; D007769:Lactams / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D008024:Ligands; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000187:drug effects*; D018000:Receptors, Peptide / Q000819:agonists / Q000037:antagonists & inhibitors / Q000187:drug effects*; D013329:Structure-Activity Relationship; D014162:Transfection; D000521:alpha-MSH / Q000737:chemistry*
chemical_list: D007769:Lactams; D008024:Ligands; D010456:Peptides, Cyclic; D044104:Receptor, Melanocortin, Type 3; D044105:Receptor, Melanocortin, Type 4; D018043:Receptors, Corticotropin; D018000:Receptors, Peptide; D000521:alpha-MSH; D000262:Adenylyl Cyclases