title: Cannabinoid CB1 receptor elevation of intracellular calcium in neuroblastoma SH-SY5Y cells: interactions with muscarinic and delta-opioid receptors.
abstract: Although coupled to G(i/o) proteins, cannabinoid CB(1) receptors can also activate intracellular Ca(2+) ([Ca(2+)](i)) accumulation through not fully understood mechanisms. We report that in, human neuroblastoma SH-SY5Y cells, CB(1) activation with the specific agonist arachidonoylchloroethanolamide (ACEA), weakly elevates [Ca(2+)](i) and that this effect, when using low (1-100 nM) concentrations of ACEA, is enhanced by the previous activation of G(q/11)-coupled M(3) muscarinic receptors with carbachol, dose-dependently and up to approximately 8-fold. A similar behaviour was also observed with carbachol and the G(i/o)-coupled delta-opioid receptor. Furthermore, stimulation of CB(1) receptors produced a concentration-dependent leftward shift of the elevation of [Ca(2+)](i) by delta-opioid receptors. These stimulatory effects were variedly attenuated by selective antagonists of each receptor, pertussis toxin, inhibitors of phospholipase C (U73122 and D609), and, when assessed in the presence of extracellular Ca(2+), by the block of voltage-activated calcium channels. Cholera toxin only slightly inhibited the G(q/11)-G(i/o)-mediated cross-talk, but induced a stronger inhibition of the G(i/o)-G(i/o)-mediated interaction. These findings suggest that activation of M(3) muscarinic receptors might produce a qualitative alteration of the signaling associated with G(i/o)-coupled receptors, and that sequential activation of CB(1) and delta-opioid receptors, both coupled to G(i/o), produces instead synergistic effects on [Ca(2+)](i) elevation.
authors.affiliation: Institute of Biomolecular Chemistry, National Research Council, Via Campi Flegrei 34, Comprensorio Olivetti, Pozzuoli, Naples, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Marini
authors.forename: Aniello Schiano
authors.initials: AS
authors.lastname: Moriello
authors.forename: Luigia
authors.initials: L
authors.lastname: Cristino
authors.forename: Maura
authors.initials: M
authors.lastname: Palmery
authors.forename: Luciano
authors.initials: L
authors.lastname: De Petrocellis
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Di Marzo
mesh_terms: D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D043587:Receptor, Muscarinic M3 / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism*; D017465:Receptors, Opioid, delta / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D043884:Receptor, Cannabinoid, CB1; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic; D017465:Receptors, Opioid, delta; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium