Cannabinoid Receptor 2 Phosphorylation Assays
Cannabinoid CB2 receptor mRNA can be found in spleen, tonsils, bone marrow, pancreas, splenic macrophage/monocyte preparations, peripheral blood leukocytes, and in a variety of cultured immune cell models including the myeloid cell line U937 and undifferentiated and differentiated granulocyte-like or macrophage-like HL60 cells. CB2 receptors may also be expressed by certain central and peripheral neurons. However, the role of these putative neuronal receptors has yet to be established. Signal transduction by the CB2 receptor includes PTX-sensitive inhibition of cAMP production, MAP kinase activation and immediate early gene expression. No modulation of ion channels or alterations of intracellular Ca2+ were observed in host cells expressing CB2 receptors.As to CB2-selective competitive antagonists, those most often used as experimental tools are 6-iodopravadoline (AM630) and SR144528. Both these compounds behave as CB2 receptor inverse agonists. A neutral antagonist that selectively targets the CB2 receptor has yet to be developed. CB2 receptor desensitization, β-arrestin recruitment and internalization are regulated by phosphorylation of carboxyl-terminal serine335/serine336 (pS335/pS336-CB2) and threonine338/threonine340 (pT338/pT340-CB2). This nomenclature refers to the human CB2 receptor. This phosphorylation motif is highly conserved across species and is identical in mice, rats and humans. For more information on CB2 pharmacology please refer to the IUPHAR database. For further reading refer to:
Pertwee RG, Howlett AC, Abood ME, Alexander SP, Di Marzo V, Elphick MR, Greasley PJ, Hansen HS, Kunos G, Mackie K, Mechoulam R, Ross RA. International Union of Basic and Clinical Pharmacology. LXXIX. Cannabinoid receptors and their ligands: beyond CB₁ and CB₂. Pharmacol Rev. 2010 Dec;62(4):588-631. doi: 10.1124/pr.110.003004. PMID: 21079038; PMCID: PMC2993256.