Cannabinoids Cannabinoid receptors Cannabinoid receptor:2-AG Cannabinoid receptors can bind cannabinoids Authored: Jassal, B, 2009-04-30 13:38:16 Edited: Jassal, B, 2009-04-30 13:38:16 Pubmed12037135 Pubmed17876302 Pubmed18845565 Pubmed2263478 Pubmed7498464 Pubmed7689702 Pubmed7775459 Reactome Database ID Release 43419426 Reactome, http://www.reactome.org ReactomeREACT_18279 Reviewed: D'Eustachio, P, 2009-05-29 07:44:22 The cannabinoid receptors are a class of receptors within the G-protein coupled receptor superfamily. Their ligands are known as cannabinoids or endocannabinoids depending on whether they come from external or internal (endogenous) sources, respectively (Howlett AC et al, 2002). Endocannabinoids serve as intercellular lipid messengers, signaling molecules that are released from one cell and activate the cannabinoid receptors present on other cells. <br>Cannabinoid type 1 (CB1) receptors (Gerrard C et al, 1990) are thought to be the most widely expressed G-protein coupled receptors in the brain, lungs, liver and kidneys. Endocannabinoids released from the depolarized neuron bind to CB1 receptors in the pre-synaptic neuron and cause a reduction in GABA release.<br>CB2 receptors (Munro S et al, 1993) are mainly expressed on T cells of the immune system, on macrophages and B cells, and in hematopoietic cells. Current research suggests that these receptors play a role in nociception, or the perception of pain.<br>Both receptors' activity is mediated by coupling to the G protein alpha i/o subunit, which inhibits adenylyl cyclase (Bouaboula M et al, 1995; Bayewitch M et al, 1995).<br>GPR55 is activated by plant cannabinoids and the endocannabinoids 2-arachidonoyl glycerol (2-AG) and anandamide, leading to suggestions that it shold be renamed CB3. However GPR55 has also been reported as a receptor for LPI and its derivative 2-Arachidonoyl-sn-glycero-3-phosphoinositol. <br> 2-AG binds to the CB1 and CB2 receptors with similar affinity, acting as a full agonist.