In vitro activity: Org 27569 is an allosteric modulator of CB1 cannabinoid receptor. It significantly increases the binding of CB1 receptor agonist and causes a significant decrease in specific binding of CB1 receptor inverse agonist. Org 27569 induces CB1 high affinity agonist binding, receptor internalization, and downstream ERK phosphorylation. The allosteric ligand Org 27569 promotes agonist binding to CB1, yet blocks the agonist-induced conformational changes in TM6. Org 27569 traps the receptor in a distinct agonist-bound, but nonsignaling conformational state.

Kinase Assay: Binding assays are performed with the CB1 receptor agonist [3H]CP 55,940 (0.7 nM) and the CB1 receptor antagonist [3H]SR 141716A (1.2 nM), 1 mg/ml BSA and 50 mM Tris buffer containing 0.1 mM EDTA and 0.5 mM MgCl2, pH 7.4, in a total assay volume of 500 μl. Binding is initiated by the addition of mouse brain membranes (30 μg). Assays are carried out at 37°C for 60 min before termination by addition of ice-cold wash buffer (50 mM Tris buffer and 1 mg/ml BSA) and vacuum filtration using a 24-well sampling manifold and Whatman GF/B glass-fiber filters that have been soaked in wash buffer at 4°C for 24 h. Each reaction tube is washed five times with a 4-ml aliquot of buffer. The filters are oven-dried for 60 min and then placed in 5 ml of scintillation fluid, and radioactivity is quantitated by liquid scintillation spectrometry. Specific binding is defined as the difference between the binding that occurred in the presence and absence of 1 μM concentrations of the corresponding unlabeled ligand and is 70 to 80% of the total binding.

Cell Assay: Cells expressing CB1 receptors are exposed to ORG27569 (10 μM) for 5 to 15 min. For toxin treatment to abrogate Gi coupling effects, PTX is added to the medium at 5 ng/ml. Following an 18-h incubation in the presence of toxin, cells are washed twice with PBS and treated with compounds. Cells are washed with ice-cold PBS, and cell lysates are obtained by harvesting the cells with ice-cold lysis buffer (150 mM NaCl, 1.0% IGEPAL CA-630, 0.5% sodium deoxycholate, 0.1% SDS, and 50 mM Tris, pH 7.5 containing 4-(2-aminoethyl)benzenesulfonyl fluoride, pepstatin A, E-64, bestatin, leupeptin, and aprotinin as protease inhibitors).

Mol Pharmacol. 2005 Nov;68(5):1484-95; J Biol Chem. 2012 Apr 6;287(15):12070-82.