The G_12/13-RhoA signaling pathway contributes to efficient lysophosphatidic acid-stimulated cell migration

The membrane redistribution and phosphorylation of focal adhesion kinase (FAK) have been reported to be important for cell migration. We previously showed that Lysophosphatidic acid (LPA) induced FAK membrane redistribution and autophosphorylation in ovarian cancer SK-OV3 cells and the signaling pathway consisting of G_i-Ras-MEKK1 mediated LPA-induced FAK membrane redistribution but not FAK autophosphorylation. We also showed that the disruption of the G_i-Ras-MEKK1 pathway led to a significant reduction in LPA-stimulated cell migration. These findings raised the question of whether LPA-induced FAK autophosphorylation was required for LPA-stimulated cell migration and what signaling mechanism was involved in LPA-induced FAK autophosphorylation. In this study, we expressed the membrane anchored wild-type FAK (CD2-FAK) in SK-OV3 cells and found that the expression of CD2-FAK greatly rescued LPA-stimulated cell migration in G_i or Ras-inhibited cells. However, G_i inhibitor pertussis toxin or dominant-negative H-Ras still significantly inhibited LPA-stimulated cell migration in cells expressing the membrane anchored FAK containing a mutation in the autophosphorylation site [CD2-FAK(Y397A)]. These results suggest that FAK autophosphorylation plays a role in LPA-stimulated cell migration. With the aid of p115Rho-GEF-RGS, G ₁₂ and G₁₃ minigenes to inhibit G_12/13, we found that the G_12/13 pathway was required for LPA-induced FAK autophosphorylation and efficient cell migration. Moreover, LPA activated RhoA and Rho kinase (ROCK) in a G_12/13-dependent manner and their activities were required for LPA-induced FAK autophosphorylation. However, Rho or ROCK inhibitors displayed no effect on LPA-induced FAK membrane redistribution although they abolished LPA-induced cytoskeleton reorganization. Our studies show that the G_12/13-RhoA-ROCK signaling pathway mediates LPA-induced FAK autophosphorylation and contributes to LPA-stimulated cell migration.