title: Brominated cyclodipeptides from the marine sponge Geodia barretti as selective 5-HT ligands.
abstract: The brominated cyclodipeptides barettin (cyclo[(6-bromo-8-entryptophan)arginine]) and 8,9-dihydrobarettin (cyclo[(6-bromotryptophan)arginine]) isolated from the marine sponge Geodia barretti have previously been shown to inhibit settlement of barnacle larvae in a dose-dependent manner in concentrations ranging from 0.5 to 25 microM. To further establish the molecular target and mode of action of these compounds, we investigated their affinity to human serotonin receptors. The tryptophan residue in the barettins resembles that of endogenous serotonin [5-hydroxytryptamine]. A selection of human serotonin receptors, including representatives from all subfamilies (1-7), were transfected into HEK-293 cells. Barettin selectively interacted with the serotonin receptors 5-HT2A, 5-HT2C, and 5-HT4 at concentrations close to that of endogenous serotonin, with the corresponding Ki values being 1.93, 0.34, and 1.91 microM, respectively. 8,9-Dihydrobarettin interacted exclusively with the 5-HT2C receptor with a Ki value of 4.63 microM; it failed to show affinity to 5-HT2A and 5-HT4, indicating that the double bond between the tryptophan and arginine residue plays an important role in the interaction with the receptor proteins.
authors.affiliation: Division of Pharmacognosy, Department of Medicinal Chemistry, Biomedical Centre, Uppsala University, SE-751 23 Uppsala, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Hedner
authors.forename: Martin
authors.initials: M
authors.lastname: Sjögren
authors.forename: Per-Anders
authors.initials: PA
authors.lastname: Frändberg
authors.forename: Tobias
authors.initials: T
authors.lastname: Johansson
authors.forename: Ulf
authors.initials: U
authors.lastname: Göransson
authors.forename: Mia
authors.initials: M
authors.lastname: Dahlström
authors.forename: Per
authors.initials: P
authors.lastname: Jonsson
authors.forename: Fred
authors.initials: F
authors.lastname: Nyberg
authors.forename: Lars
authors.initials: L
authors.lastname: Bohlin
mesh_terms: D000818:Animals; D004151:Dipeptides / Q000737:chemistry / Q000302:isolation & purification / Q000493:pharmacokinetics / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006842:Hydrocarbons, Brominated / Q000737:chemistry / Q000302:isolation & purification / Q000493:pharmacokinetics / Q000494:pharmacology; D007668:Kidney / Q000166:cytology; D007814:Larva / Q000187:drug effects; D008386:Marine Biology; D015394:Molecular Structure; D010456:Peptides, Cyclic / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D011161:Porifera / Q000737:chemistry*; D011985:Receptors, Serotonin / Q000187:drug effects*; D001468:Thoracica / Q000187:drug effects*
chemical_list: D004151:Dipeptides; D006842:Hydrocarbons, Brominated; D010456:Peptides, Cyclic; D011985:Receptors, Serotonin; C484472:barettin