title: A "locked-on," constitutively active mutant of the adenosine A1 receptor.
abstract: We studied the wild-type human adenosine A1 receptor and three mutant receptors, in which the glycine at position 14 had been changed into an alanine, a leucine, or a threonine residue. All receptors were characterized in radioligand binding experiments, the wild-type and the Gly14Thr mutant receptor in greater detail. Both receptors were allosterically modulated by sodium ions and PD81,723 (2-amino-4,5-dimethyl-3-thienyl-[3(trifluoromethyl)-phenyl]methanone), although in a different way. All mutant receptors appeared to be spontaneously or "constitutively" active in a [35S]GTPgammaS binding assay, the first demonstration of the existence of such CAM (constitutively active mutant) receptors for the adenosine A1 receptor. The Gly14Thr mutant receptor was also constitutively active in another functional assay, i.e., the inhibition of forskolin-induced cAMP production in intact cells. Importantly, this mutant displayed a peculiar "locked-on" phenotype, i.e., neither agonist nor inverse agonist was capable of modulating the basal activity in both the GTPgammaS and the cAMP assay, unlike the wild-type and the two other mutant receptors.
authors.affiliation: Division of Medicinal Chemistry, Leiden/Amsterdam Center for Drug Research, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
authors.forename: Rianne A F
authors.initials: RA
authors.lastname: de Ligt
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rivkees
authors.forename: Anna
authors.initials: A
authors.lastname: Lorenzen
authors.forename: Rob
authors.initials: R
authors.lastname: Leurs
authors.forename: Ad P
authors.initials: AP
authors.lastname: IJzerman
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002522:Chlorocebus aethiops; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D011869:Radioligand Assay; D043682:Receptor, Adenosine A1 / Q000235:genetics* / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology; D013462:Sulfur Radioisotopes; D013806:Theophylline / Q000031:analogs & derivatives* / Q000494:pharmacology; D013876:Thiophenes / Q000494:pharmacology; D014162:Transfection; D014316:Tritium; D014970:Xanthines / Q000378:metabolism / Q000494:pharmacology
chemical_list: D043682:Receptor, Adenosine A1; D013462:Sulfur Radioisotopes; D013876:Thiophenes; D014970:Xanthines; D014316:Tritium; C075004:PD 81723; D005576:Colforsin; C053907:8-cyclopentyl-1,3-dimethylxanthine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C048599:N(6)-cyclopentyladenosine; D006160:Guanosine Triphosphate; D012964:Sodium; C051360:1,3-dipropyl-8-cyclopentylxanthine; D013806:Theophylline; D000242:Cyclic AMP; D000241:Adenosine