Hematopoietic cells expressing the peripheral cannabinoid receptor migrate in response to the endocannabinoid 2-arachidonoylglycerol.
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.
Jordà
Meritxell Alberich
MA
Institute for Hematology, Erasmus University Rotterdam, The Netherlands.
Verbakel
Sandra E
SE
Valk
Peter J M
PJ
Vankan-Berkhoudt
Yolanda V
YV
Maccarrone
Mauro
M
Finazzi-Agrò
Allessandro
A
Löwenberg
Bob
B
Delwel
Ruud
R
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
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