Differential coupling of the human cannabinoid receptors hCB1R and hCB2R to the G-protein G(alpha)i2beta1gamma2.
Human cannabinoid receptors 1 (hCB(1)R) and 2 (hCB(2)R) are expressed in the CNS and couple to G(i)/G(o)-proteins. The aim of this study was to compare coupling of hCB(1)R and hCB(2)R to G(alpha)(i2)beta(1)gamma(2) in Sf9 insect cells. High-affinity agonist binding at hCB(1)R, but not at hCB(2)R, was resistant to guanine nucleotides. hCB(1)R activated G(alpha)(i2)beta(1)gamma(2) much more rapidly than hCB(2)R in the [(35)S]guanosine 5'-[gamma-thio]triphosphate ([(35)S]GTPgammaS) binding assay. Moreover, hCB(1)R exhibited a higher constitutive activity than hCB(2)R as assessed by the relative inhibitory effects of inverse agonists on [(35)S]GTPgammaS binding and steady-state high-affinity GTPase activity compared to the stimulatory effects of the hCB(1/2)R agonist CP 55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol]. G(alpha)(i2)beta(1)gamma(2) coupled to hCB(2)R exhibited higher GDP- and GTPgammaS-affinities than G(alpha)(i2)beta(1)gamma(2) coupled to hCB(1)R. NaCl effectively reduced constitutive activity of hCB(1)R but not of hCB(2)R. Collectively, hCB(1)R and hCB(2)R couple differentially to G(alpha)(i2)beta(1)gamma(2). Moreover, hCB(1)R exhibits higher constitutive activity than hCB(2)R. These differences point to distinct functions of hCB(1)R and hCB(2)R in the CNS.
Nickl
Kathrin
K
Department of Pharmaceutical Biology, University of Regensburg, Regensburg, Germany.
Gardner
Eric E
EE
Geiger
Sarah
S
Heilmann
Jörg
J
Seifert
Roland
R
D000818:Animals; D002461:Cell Line, Transformed; D003511:Cyclohexanols / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D020558:GTP Phosphohydrolases / Q000378:metabolism; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000235:genetics / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000235:genetics / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000493:pharmacokinetics; D006801:Humans; D007313:Insecta; D011485:Protein Binding / Q000187:drug effects; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists / Q000378:metabolism*; D043885:Receptor, Cannabinoid, CB2 / Q000378:metabolism*; D013997:Time Factors
D003511:Cyclohexanols; D044388:GTP-Binding Protein gamma Subunits; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D020558:GTP Phosphohydrolases; D051960:GTP-Binding Protein alpha Subunit, Gi2