PT  - JOURNAL ARTICLE
AU  - D M Slipetz
AU  - G P O'Neill
AU  - L Favreau
AU  - C Dufresne
AU  - M Gallant
AU  - Y Gareau
AU  - D Guay
AU  - M Labelle
AU  - K M Metters
TI  - Activation of the human peripheral cannabinoid receptor results in inhibition of adenylyl cyclase.
DP  - 1995 Aug 01
TA  - Molecular Pharmacology
PG  - 352--361
VI  - 48
IP  - 2
4099  - http://molpharm.aspetjournals.org/content/48/2/352.short
4100  - http://molpharm.aspetjournals.org/content/48/2/352.full
SO  - Mol Pharmacol1995 Aug 01; 48
AB  - The human peripheral cannabinoid (CB2) receptor has been cloned by reverse transcription-polymerase chain reaction from human spleen RNA and expressed, to study both ligand binding characteristics and signal transduction pathways. Receptor binding assays used the aminoalkylindole [3H]Win 55212-2 and membranes from transiently transfected COS-M6 cells. Saturation analysis showed that [3H]Win 55212-2 specific binding to the CB2 receptor was of high affinity, with a Kd of 2.1 +/- 0.2 nM (four experiments), and a high level of expression was attained, with a maximal number of saturable binding sites of 24.1 +/- 4.4 pmol/mg of protein (four experiments). The rates of association and dissociation for [3H]Win 55212-2 specific binding were both rapid when measured at 30 degrees. [3H]Win 55212-2 specific binding to the CB2 receptor was moderately enhanced by divalent and monovalent cations but was only slightly inhibited by guanosine-5'-O-(3-thio)-triphosphate. Competition for [3H]Win 55212-2 specific binding to the CB2 receptor was stereoselective, with the following rank order of potency for the more active stereoisomers: HU-210 > (-)-CP-55940 approximately Win 55212-2 > (-)delta 9-THC > anandamide. The signaling pathway of the human CB2 receptor was investigated in a CB2-CHO-K1 stable cell line. CB2 receptor activation by cannabinoid agonists inhibited forskolin-induced cAMP production in a concentration-dependent and stereoselective manner but did not increase either cAMP production or Ca2+ mobilization in fura-2/acetoxymethyl ester-loaded CB2-CHO-K1 cells. The CB2 receptor-mediated inhibition of forskolin-induced cAMP production was abolished by pretreatment of the cells with 10 ng/ml pertussis toxin. These results demonstrate that the CB2 receptor is functionally coupled to inhibition of adenylyl cyclase activity via a pertussis toxin-sensitive G protein.