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.

*Arachidonic Acids, Animals, B-Lymphocytes/drug effects/metabolism, Cannabinoids/pharmacology, Chemotaxis/*drug effects, Cytokines/pharmacology, Drug Interactions, Endocannabinoids, Glycerides/*pharmacology, Leukemia, Myeloid/pathology, Ligands, Mice, Myeloid Cells/chemistry/*drug effects, Receptors, Cannabinoid, Receptors, Drug/genetics/*physiology, Research Support, Non-U.S. Gov't, Spleen/cytology, Thymus Gland/cytology, Transfection, Tumor Cells, Cultured
Erasmus MC: University Medical Center Rotterdam

Alberich-Jorda, M, Verbakel, S.E, Valk, P.J.M, Vankan-Berkhoudt, Y.V, Maccarrone, M, Finazzi-Agro, A, … Delwel, H.R. (2002). Hematopoietic cells expressing the peripheral cannabinoid receptor migrate in response to the endocannabinoid 2-arachidonoylglycerol. Blood. Retrieved from http://hdl.handle.net/1765/8225