title: Hematopoietic cells expressing the peripheral cannabinoid receptor migrate in response to the endocannabinoid 2-arachidonoylglycerol.
abstract: Cb2 is a novel protooncogene encoding the peripheral cannabinoid receptor. Previous studies demonstrated that 2 distinct noncoding first exons exist: exon-1A and exon-1B, which both splice to protein-coding exon-2. We demonstrate that in retrovirally induced murine myeloid leukemia cells with proviral insertion in Cb2, exon-1B/exon-2 Cb2 messenger RNA levels have been increased, resulting in high receptor numbers. In myeloid leukemia cells without virus insertion in this locus, low levels of only exon-1A/exon-2 Cb2 transcripts were present and receptors could not be detected. To elucidate the function of Cb2 in myeloid leukemia cells, a set of in vitro experiments was carried out using 32D/G-CSF-R (granulocyte colony-stimulating factor receptor) cells transfected with exon-1B/exon-2 Cb2 complementary DNA and a myeloid cell line carrying a virus insertion in Cb2 (ie, NFS 78). We demonstrate that a major function of the Cb2 receptor is stimulation of migration as determined in a transwell assay. Exposure of Cb2-expressing cells to different cannabinoids showed that the true ligand for Cb2 is 2-arachidonoylglycerol (2-AG), which may act as chemoattractant and as a chemokinetic agent. Furthermore, we observed a significant synergistic activity between 2-AG and interleukin-3 or G-CSF, suggesting cross-talk between the different receptor systems. Radioactive-ligand binding studies revealed significant numbers of Cb2 receptors in normal spleen. Transwell experiments carried out with normal mouse spleen cells showed 2-AG-induced migration of B220-, CD19-, immunoglobulin M-, and immunoglobulin D-expressing B lymphocytes. Our study demonstrates that a major function of Cb2 receptor expressed on myeloid leukemia cells or normal splenocytes is stimulation of migration.
authors.affiliation: Institute for Hematology, Erasmus University Rotterdam, The Netherlands.
authors.forename: Meritxell Alberich
authors.initials: MA
authors.lastname: Jordà
authors.forename: Sandra E
authors.initials: SE
authors.lastname: Verbakel
authors.forename: Peter J M
authors.initials: PJ
authors.lastname: Valk
authors.forename: Yolanda V
authors.initials: YV
authors.lastname: Vankan-Berkhoudt
authors.forename: Mauro
authors.initials: M
authors.lastname: Maccarrone
authors.forename: Allessandro
authors.initials: A
authors.lastname: Finazzi-Agrò
authors.forename: Bob
authors.initials: B
authors.lastname: Löwenberg
authors.forename: Ruud
authors.initials: R
authors.lastname: Delwel
mesh_terms: D000818:Animals; D001095:Arachidonic Acids; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids / Q000494:pharmacology; D002633:Chemotaxis / Q000187:drug effects*; D016207:Cytokines / Q000494:pharmacology; D004347:Drug Interactions; D063388:Endocannabinoids; D005989:Glycerides / Q000494:pharmacology*; D007951:Leukemia, Myeloid / Q000473:pathology; D008024:Ligands; D051379:Mice; D022423:Myeloid Cells / Q000737:chemistry / Q000187:drug effects*; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000235:genetics / Q000502:physiology*; D013154:Spleen / Q000166:cytology; D013950:Thymus Gland / Q000166:cytology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids; D016207:Cytokines; D063388:Endocannabinoids; D005989:Glycerides; D008024:Ligands; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C094503:glyceryl 2-arachidonate