Sphingosine-1-phosphate receptor subtype-specific positive and negative regulation of Rac and haematogenous metastasis of melanoma cells

Abstract

We have recently reported that S1P (sphingosine-1-phosphate) differentially regulates cellular Rac activity and cell migration in either a positive or a negative direction via distinct G-protein-coupled receptor subtypes, i.e. S1P1/Edg1 (endothelial differentiation gene) and S1P2/Edg5 respectively, when each of the S1P receptor subtypes is expressed in CHO (Chinese-hamster ovary) cells. In B16F10 mouse melanoma cells, in which S1P2, but not the other S1P receptor subtypes, is endogenously expressed, S1P inhibited cell migration with concomitant inhibition of Rac and stimulation of RhoA in dose-dependent manners. Overexpression of S1P2 in the melanoma cells resulted in potentiation of S1P inhibition of both Rac and cell migration. In contrast, overexpression of S1P1 led to stimulation of cell migration, particularly at the lower S1P concentrations. Treatment of B16F10 cells with S1P inhibited lung metastasis 3 weeks after injection into mouse tail veins. Intriguingly, overexpression of S1P2 greatly potentiated the inhibition of metastasis by S1P, whereas that of S1P1 resulted in aggravation of metastasis. Suppression of cellular Rac activity by adenovirus-transduced expression of N17Rac, but not N19RhoA, strongly inhibited cell migration in vitro and lung metastasis in vivo. These results provide the first evidence that G-protein-coupled receptors could participate in the regulation of metastasis, in which ligand-dependent, subtype-specific regulation of the cellular Rac activity is probably critically involved as a mechanism.

S1P induced changes in epithelial ovarian cancer proteolysis, invasion, and attachment are mediated by Gi and Rac

“…Using mouse melanoma cells S1P1 mediated increased migration particularly at low concentrations [31]. Similar to our findings, Takuwa et.…”

“…Similar to our findings, Takuwa et. al [30] found in chinese hamster ovarian cells and B16-F10 mouse melanoma cells that Rac activation is regulated in the same direction as migration by S1P; and, that while Rac activation via S1P1 and S1P3 is Gi dependent, Rac inhibition via S1P2 is not [31].…”

Roles of sphingosine-1-phosphate (S1P) receptors in malignant behavior of glioma cells. Differential effects of S1P2 on cell migration and invasiveness

“…In particular, S1P 1 stimulates migration through Rac activation and lamellipodia formation, while S1P 2 blocks migration through Rho activation, which in many cell types leads to inhibition of Rac [16][17][18]. In U-118 MG cells S1P 2 does not inhibit Rac activation, however it does activate Rho ( [19] and Fig.…”

“…While S1P 2 is known to decrease cell motility [16][17][18], the increase in S1P-stimulated invasiveness due to S1P 2 overexpression represents a novel finding. The targeted decrease in S1P 2 expression in U-373 MG cells had no effect on cell motility, suggesting that the motility response of U-373 MG cells to S1P is dominated by the pro-migration effects of S1P 1 and S1P 3 .…”

“…Thus, these results confirm that S1P 2 overexpression enhances invasiveness of U-118 MG cells. S1P 2 has been shown to inhibit cell migration through blocking activation of the small GTPase Rac in several cell types, and this response is mediated through Rho [16][17][18]. Interestingly, although S1P 2 has also been shown to block migration of glioma cells, and to activate Rho, it failed to inhibit Rac activation in these cells [19].…”