title: Divergent pharmacological activity of novel marine-derived excitatory amino acids on glutamate receptors.
abstract: Kainate receptors show a particular affinity for a variety of natural source compounds, including dysiherbaine (DH), a potent agonist derived from the marine sponge Dysidea herbacea. In this study, we characterized the pharmacological activity and structural basis for subunit selectivity of neodysiherbaine (neoDH) and MSVIII-19, which are natural and synthetic analogs of DH, respectively. NeoDH and MSVIII-19 differ from DH in the composition of two functional groups that confer specificity and selectivity for ionotropic glutamate receptors. In radioligand binding assays, neoDH displayed a 15- to 25-fold lower affinity relative to that of DH for glutamate receptor (GluR)5 and GluR6 kainate receptor subunits but a 7-fold higher affinity for kainate (KA)2 subunits, whereas MSVIII-19 displaced [(3)H]kainate only from GluR5 subunits but not GluR6 or KA2 subunits. NeoDH was an agonist for kainate and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in patch-clamp recordings; in contrast, MSVIII-19 acted as a potent antagonist for homomeric GluR5 receptor currents with weaker activity on other kainate and AMPA receptors. Neither neoDH nor MSVIII-19 activated group I metabotropic GluRs. Homology modeling suggests that two critical amino acids confer the high degree of selectivity between the dysiherbaine analogs and the GluR5 and KA2 subunits. In summary, these data describe the pharmacological activity of two new compounds, one of which is a selective GluR5 receptor antagonist that will be of use for understanding native receptor function and designing more selective ligands for kainate receptors.
authors.affiliation: Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, 77555, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Sanders
authors.forename: Koichi
authors.initials: K
authors.lastname: Ito
authors.forename: Luca
authors.initials: L
authors.lastname: Settimo
authors.forename: Olli T
authors.initials: OT
authors.lastname: Pentikäinen
authors.forename: Muneo
authors.initials: M
authors.lastname: Shoji
authors.forename: Makoto
authors.initials: M
authors.lastname: Sasaki
authors.forename: Mark S
authors.initials: MS
authors.lastname: Johnson
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Sakai
authors.forename: Geoffrey T
authors.initials: GT
authors.lastname: Swanson
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D002478:Cells, Cultured; D018846:Excitatory Amino Acids / Q000494:pharmacology*; D006801:Humans; D007608:Kainic Acid / Q000378:metabolism; D008958:Models, Molecular; D018091:Receptors, AMPA / Q000819:agonists / Q000037:antagonists & inhibitors; D017470:Receptors, Glutamate / Q000187:drug effects*; D018092:Kainic Acid Receptors / Q000819:agonists / Q000037:antagonists & inhibitors; D018094:Receptors, Metabotropic Glutamate / Q000187:drug effects
chemical_list: D000409:Alanine; D019086:Bridged Bicyclo Compounds, Heterocyclic; D018846:Excitatory Amino Acids; D007608:Kainic Acid; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D018092:Kainic Acid Receptors; D018094:Receptors, Metabotropic Glutamate; C121741:dysiherbaine; C104077:metabotropic glutamate receptor type 1; C438974:neodysiherbaine A