title: CB2 cannabinoid receptor targets mitogenic Gi protein-cyclin D1 axis in osteoblasts.
abstract: CB2 is a Gi protein-coupled receptor activated by endo- and phytocannabinoids, thus inhibiting stimulated adenylyl cyclase activity. CB2 is expressed in bone cells and Cb2 null mice show a marked age-related bone loss. CB2-specific agonists both attenuate and rescue ovariectomy-induced bone loss. Activation of CB2 stimulates osteoblast proliferation and bone marrow derived colony-forming units osteoblastic. Here we show that selective and nonselective CB2 agonists are mitogenic in MC3T3 E1 and newborn mouse calvarial osteoblastic cultures. The CB2 mitogenic signaling depends critically on the stimulation of Erk1/2 phosphorylation and de novo synthesis of MAP kinase-activated protein kinase 2 (Mapkapk2) mRNA and protein. Further downstream, CB2 activation enhances CREB transcriptional activity and cyclin D1 mRNA expression. The CB2-induced stimulation of CREB and cyclin D1 is inhibitable by pertussis toxin, the MEK-Erk1/2 inhibitors PD098059 and U0126, and Mapkapk2 siRNA. These data demonstrate that in osteoblasts CB2 targets a Gi protein-cyclin D1 mitogenic axis. Erk1/2 phosphorylation and Mapkapk2 protein synthesis are critical intermediates in this axis.
authors.affiliation: Bone Laboratory, Hebrew University of Jerusalem, Jerusalem, Israel.
authors.forename: Orr
authors.initials: O
authors.lastname: Ofek
authors.forename: Malka
authors.initials: M
authors.lastname: Attar-Namdar
authors.forename: Vardit
authors.initials: V
authors.lastname: Kram
authors.forename: Mona
authors.initials: M
authors.lastname: Dvir-Ginzberg
authors.forename: Raphael
authors.initials: R
authors.lastname: Mechoulam
authors.forename: Andreas
authors.initials: A
authors.lastname: Zimmer
authors.forename: Baruch
authors.initials: B
authors.lastname: Frenkel
authors.forename: Esther
authors.initials: E
authors.lastname: Shohami
authors.forename: Itai
authors.initials: I
authors.lastname: Bab
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D019938:Cyclin D1 / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008934:Mitogens / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010006:Osteoblasts / Q000201:enzymology* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2 / Q000378:metabolism*
chemical_list: D002070:Butadienes; D005419:Flavonoids; D008934:Mitogens; D009570:Nitriles; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D043885:Receptor, Cannabinoid, CB2; C113580:U 0126; D019938:Cyclin D1; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
references.citation: Nat Med. 2005 Jul;11(7):774-9
references.pmid: 15908955
references.citation: J Neuroendocrinol. 2008 May;20 Suppl 1:10-4
references.pmid: 18426493
references.citation: EMBO J. 1996 Sep 2;15(17):4629-42
references.pmid: 8887554
references.citation: Bone. 2005 Jan;36(1):93-100
references.pmid: 15664007
references.citation: J Biol Chem. 2001 Mar 9;276(10):7586-92
references.pmid: 11108712
references.citation: Curr Opin Cell Biol. 1997 Apr;9(2):180-6
references.pmid: 9069255
references.citation: J Bone Miner Res. 2003 Nov;18(11):2060-8
references.pmid: 14606520
references.citation: J Cell Biol. 1998 Jul 27;142(2):523-35
references.pmid: 9679149
references.citation: J Cell Biol. 2002 Apr 15;157(2):303-14
references.pmid: 11956231
references.citation: EMBO J. 1997 Apr 15;16(8):1921-33
references.pmid: 9155018
references.citation: J Neuroendocrinol. 2008 May;20 Suppl 1:69-74
references.pmid: 18426503
references.citation: Trends Pharmacol Sci. 2007 Apr;28(4):173-9
references.pmid: 17350109
references.citation: J Bone Miner Res. 2002 Aug;17(8):1401-7
references.pmid: 12162494
references.citation: FASEB J. 2010 Mar;24(3):788-98
references.pmid: 19884325
references.citation: J Cell Biochem. 2004 Nov 1;93(4):741-52
references.pmid: 15660418
references.citation: Endocrinology. 2008 Nov;149(11):5619-26
references.pmid: 18635663
references.citation: Bone. 2009 Oct;45(4):716-25
references.pmid: 19560570
references.citation: Curr Opin Cell Biol. 1995 Dec;7(6):798-805
references.pmid: 8608010
references.citation: Br J Pharmacol. 2008 Jan;153(2):347-57
references.pmid: 17994109
references.citation: Am J Physiol. 1997 May;272(5 Pt 1):C1709-16
references.pmid: 9176163
references.citation: J Cell Biochem. 2001;81(4):594-603
references.pmid: 11329614
references.citation: EMBO J. 1995 Dec 1;14(23):5920-30
references.pmid: 8846784
references.citation: Eur J Pharmacol. 2000 May 19;396(2-3):141-9
references.pmid: 10822068
references.citation: Proc Natl Acad Sci U S A. 2006 Jan 17;103(3):696-701
references.pmid: 16407142
references.citation: Proc Natl Acad Sci U S A. 2005 Sep 6;102(36):12956-61
references.pmid: 16126903
references.citation: Handb Exp Pharmacol. 2005;(168):53-79
references.pmid: 16596771
references.citation: Proc Natl Acad Sci U S A. 1999 Dec 7;96(25):14228-33
references.pmid: 10588688
references.citation: Nat Rev Drug Discov. 2008 May;7(5):438-55
references.pmid: 18446159
references.citation: J Cell Biochem. 2003 Feb 15;88(3):446-54
references.pmid: 12532321
references.citation: J Bone Miner Res. 2001 Jun;16(6):1045-55
references.pmid: 11393781
references.citation: Cell. 2008 Nov 28;135(5):825-37
references.pmid: 19041748
references.citation: Mol Pharmacol. 1995 Sep;48(3):443-50
references.pmid: 7565624
references.citation: Structure. 2003 Jun;11(6):611-2
references.pmid: 12791249
references.citation: J Biol Chem. 2001 Jun 15;276(24):21351-8
references.pmid: 11292824
references.citation: Mol Pharmacol. 2006 Sep;70(3):786-92
references.pmid: 16772520
references.citation: Front Biosci. 1998 Aug 01;3:d804-16
references.pmid: 9682034
references.citation: FEBS Lett. 1995 May 8;364(2):229-33
references.pmid: 7750577
references.citation: Cell. 1995 Jan 27;80(2):179-85
references.pmid: 7834738
references.citation: J Biol Chem. 2004 Jul 9;279(28):29121-9
references.pmid: 15128746
references.citation: J Bone Miner Res. 2007 Jul;22(7):951-64
references.pmid: 17501623
references.citation: J Biol Chem. 2005 Nov 11;280(45):37495-502
references.pmid: 16150701
references.citation: Oncogene. 1994 Apr;9(4):1295-304
references.pmid: 8134134
references.citation: Biochem J. 2007 Jan 15;401(2):485-95
references.pmid: 16989639
references.citation: J Biol Chem. 1996 Apr 26;271(17):9902-5
references.pmid: 8626625
references.citation: Cell. 1994 Sep 23;78(6):1027-37
references.pmid: 7923353
references.citation: J Biol Chem. 2002 Mar 1;277(9):7493-500
references.pmid: 11741978
references.citation: Oncogene. 1998 Sep 17;17(11 Reviews):1331-42
references.pmid: 9779981
references.citation: Pain. 2001 Sep;93(3):239-245
references.pmid: 11514083