title: Intracellular cannabinoid type 1 (CB1) receptors are activated by anandamide.
abstract: Recent studies have demonstrated that the majority of endogenous cannabinoid type 1 (CB(1)) receptors do not reach the cell surface but are instead associated with endosomal and lysosomal compartments. Using calcium imaging and intracellular microinjection in CB(1) receptor-transfected HEK293 cells and NG108-15 neuroblastoma × glioma cells, we provide evidence that anandamide acting on CB(1) receptors increases intracellular calcium concentration when administered intracellularly but not extracellularly. The calcium-mobilizing effect of intracellular anandamide was dose-dependent and abolished by pretreatment with SR141716A, a CB(1) receptor antagonist. The anandamide-induced calcium increase was reduced by blocking nicotinic acid-adenine dinucleotide phosphate- or inositol 1,4,5-trisphosphate-dependent calcium release and abolished when both lysosomal and endoplasmic reticulum calcium release pathways were blocked. Taken together, our results indicate that, in CB(1) receptor-transfected HEK293 cells, intracellular CB(1) receptors are functional; they are located in acid-filled calcium stores (endolysosomes). Activation of intracellular CB(1) receptors releases calcium from endoplasmic reticulum and lysosomal calcium stores. In addition, our results support a novel role for nicotinic acid-adenine dinucleotide phosphate in cannabinoid-induced calcium signaling.
authors: Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors: G Cristina
authors: GC
authors: Brailoiu
authors: Division of Biocomputing, Department of Biochemistry and Molecular Biology, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131.
authors: Tudor I
authors: TI
authors: Oprea
authors: Department of Anatomy and Cell Biology and Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, Pennsylvania 19140 and.
authors: Pingwei
authors: P
authors: Zhao
authors: Department of Anatomy and Cell Biology and Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, Pennsylvania 19140 and. Electronic address: mabood@temple.edu.
authors: Mary E
authors: ME
authors: Abood
authors: Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140. Electronic address: ebrailou@temple.edu.
authors: Eugen
authors: E
authors: Brailoiu
mesh_terms: D001095:Arachidonic Acids / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D063385:Cannabinoid Receptor Modulators / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D063388:Endocannabinoids; D011992:Endosomes / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism*; D053284:Polyunsaturated Alkamides / Q000494:pharmacology*; D043884:Receptor, Cannabinoid, CB1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D053284:Polyunsaturated Alkamides; D043884:Receptor, Cannabinoid, CB1; D002118:Calcium; C078814:anandamide