Characterization of human cannabinoid CB 2 receptor coupled to chimeric Gα qi5 and Gα qo5 proteins

• Published in: European journal of pharmacology Vol. 603; no. 1; pp. 12 - 21
• Main Authors: Malysz, John, Daza, Anthony V., Kage, Karen, Grayson, George K., Yao, Betty B., Meyer, Michael D., Gopalakrishnan, Murali
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2009
• Subjects: Calcium; Cannabinoid; CB 2 receptor agonist; Chimeric; Coupling; G protein; G-protein coupled receptor; hCB 2; Radioligand binding; hCB 2; CB 2 receptor agonist; Chimeric; Calcium; G-protein coupled receptor; Radioligand binding; Coupling; Cannabinoid; G protein
• ISSN: 0014-2999; 1879-0712
• DOI: 10.1016/j.ejphar.2008.11.047

Cannabinoid CB 2 receptors may couple to a variety of G proteins and intracellular effector systems to regulate physiological and pathophysiological processes involved in inflammatory and neuropathic pain. In this study, the coupling of cannabinoid hCB 2 receptors to Gα qo5 and Gα qi5 proteins was studied and compared by investigating the pharmacological properties of HEK-293 cells co-expressing cannabinoid hCB 2 with chimeric Gα qo5 (HEK-hCB 2-G qo5) or Gα qi5 (HEK-hCB 2-G qi5). Both cell lines were found to be amendable for measuring cannabinoid CB 2 receptor agonist evoked Ca 2+ mobilization in a high-throughput manner. Comparison of binding affinities of ligands in homogenates prepared from both cell lines revealed similar affinities for [ 3H]CP55,940 displacement with the following rank order: CP55,940 ~ WIN55,212-2 > SR144528 > JWH015 ~ AM1241 ~ AM630 > SR141617A ~ AM251. In comparison at cannabinoid hCB 1 receptors: the rank order was: SR141617A ~ CP55,940>AM251 > WIN55,212-2 > AM1241 ~ SR144528 > JWH015 ~ AM630. No significant differences in cannabinoid receptor agonist (CP55,940 ~ WIN55,212-2 > JWH015) or antagonist (SR144528 ~ AM1241 > AM630 > AM251 ~ SR141617A) profiles were observed in HEK-hCB 2-G qo5 and HEK-hCB 2-G qi5 cells as determined using intracellular Ca 2+ measurements. Experiments with HEK-hCB 2-G qi5 cells carried out by investigating interactions among CP55,940, carbachol, thapsigargin, and U73122 revealed that the mechanism of cannabinoid hCB 2 receptor coupling via chimeric G proteins to Ca 2+ mobilization involves phospholipase C-inositol trisphosphate (PLC-IP 3) and that it is less efficient in comparison to the endogenous muscarinic mediated PLC-IP 3-Ca 2+ pathway. This study demonstrates that expressed cannabinoid CB 2 receptors couple equally well to Gα qo5 and Gα qi5 proteins and that receptor agonist or antagonist pharmacology is not influenced by the nature of these coupled G proteins when heterologously expressed.