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Molecular and Cellular Biology, March 2003, p. 1534-1545, Vol. 23, No. 5
0270-7306/03/$08.00+0     DOI: 10.1128/MCB.23.5.1534-1545.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Inhibitory and Stimulatory Regulation of Rac and Cell Motility by the G12/13-Rho and Gi Pathways Integrated Downstream of a Single G Protein-Coupled Sphingosine-1-Phosphate Receptor Isoform

Naotoshi Sugimoto, Noriko Takuwa, Hiroyuki Okamoto, Sotaro Sakurada, and Yoh Takuwa*

Department of Physiology, Kanazawa University Graduate School of Medicine, Kanazawa, Ishikawa 920-8640, Japan,

Received 19 August 2002/ Returned for modification 8 October 2002/ Accepted 6 December 2002

The G protein-coupled receptors S1P2/Edg5 and S1P3/Edg3 both mediate sphingosine-1-phosphate (S1P) stimulation of Rho, yet S1P2 but not S1P3 mediates downregulation of Rac activation, membrane ruffling, and cell migration in response to chemoattractants. Specific inhibition of endogenous G{alpha}12 and G{alpha}13, but not of G{alpha}q, by expression of respective C-terminal peptides abolished S1P2-mediated inhibition of Rac, membrane ruffling, and migration, as well as stimulation of Rho and stress fiber formation. Fusion receptors comprising S1P2 and either G{alpha}12 or G{alpha}13, but not G{alpha}q, mediated S1P stimulation of Rho and also inhibition of Rac and migration. Overexpression of G{alpha}i, by contrast, specifically antagonized S1P2-mediated inhibition of Rac and migration. The S1P2 actions were mimicked by expression of V14Rho and were abolished by C3 toxin and N19Rho, but not Rho kinase inhibitors. In contrast to S1P2, S1P3 mediated S1P-directed, pertussis toxin-sensitive chemotaxis and Rac activation despite concurrent stimulation of Rho via G12/13. Upon inactivation of Gi by pertussis toxin, S1P3 mediated inhibition of Rac and migration just like S1P2. These results indicate that integration of counteracting signals from the Gi- and the G12/13-Rho pathways directs either positive or negative regulation of Rac, and thus cell migration, upon activation of a single S1P receptor isoform.

* Corresponding author. Mailing address: Department of Physiology, Kanazawa University Graduate School of Medicine, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8640, Japan. Phone: 81-76-265-2165. Fax: 81-76-234-4223. E-mail: ytakuwa{at}med.kanazawa-u.ac.jp.

Molecular and Cellular Biology, March 2003, p. 1534-1545, Vol. 23, No. 5
0022-538X/03/$08.00+0     DOI: 10.1128/MCB.23.5.1534-1545.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



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