PT  - JOURNAL ARTICLE
AU  - He, Fang
AU  - Qiao, Zhuan-Hong
AU  - Cai, Jian
AU  - Pierce, William
AU  - He, Da-Cheng
AU  - Song, Zhao-Hui
TI  - Involvement of the 90-kDa Heat Shock Protein (Hsp-90) in CB2 Cannabinoid Receptor-Mediated Cell Migration: A New Role of Hsp-90 in Migration Signaling of a G Protein-Coupled Receptor
AID  - 10.1124/mol.107.036566
DP  - 2007 Nov 01
TA  - Molecular Pharmacology
PG  - 1289--1300
VI  - 72
IP  - 5
4099  - http://molpharm.aspetjournals.org/content/72/5/1289.short
4100  - http://molpharm.aspetjournals.org/content/72/5/1289.full
SO  - Mol Pharmacol2007 Nov 01; 72
AB  - The endocannabinoid 2-arachidonoylglycerol (2-AG) enhances cell migration through the CB2 cannabinoid receptor. In this study, using an immunoprecipitation and mass spectrometry-based proteomic approach, we first identified the 90-kDa heat shock protein (Hsp90), a chaperone protein with novel signaling functions, as a CB2-interacting protein. The CB2/Hsp90 interaction was confirmed in human embryonic kidney 293 cells expressing transfected CB2 and in differentiated HL-60 cells expressing endogenous CB2, by coimmunoprecipitation and Western blot experiments, as well as by treatment with geldanamycin (GA), a specific Hsp90 inhibitor. Disruption of the CB2/Hsp90 interaction by treatment with GA or reducing Hsp90 levels with specific short interfering RNAs markedly inhibited 2-AG-induced cell migration, demonstrating that Hsp90 is crucial for 2-AG-induced cell migration. 2-AG treatment resulted in a CB2-mediated stimulation of Rac1 activity, and treatment with GA blocked 2AG-induced activation of Rac1. It is noteworthy that expression of the dominant-negative form of Rac1 reduced 2-AG-induced cell migration. These data demonstrate that 2-AG-induced activation of Rac1 is essential for 2-AG-induced cell migration, and the CB2/Hsp90 interaction is needed for 2-AG-induced activation of Rac1. Furthermore, 2-AG-induced Rac1 activation was sensitive to pertussis toxin treatment, hence involving Gi proteins. In addition, treatment with GA significantly inhibited the CB2/Gαi2 interaction. As a whole, our data indicate that Hsp90 may serve as scaffold to keep the CB2 receptor and its signaling components, including Gαi2, in proximity, thus facilitating CB2-mediated signaling to cell migration through the Gi-Rac1 pathway. By demonstrating that Hsp90 is essential for CB2-mediated signaling to cell migration, this study reveals a novel role of Hsp90 in the signaling events mediated by a G protein-coupled receptor. The American Society for Pharmacology and Experimental Therapeutics