Cooperation of G sub(q), G sub(i), and G sub(12/13) in Protein Kinase D Activation and Phosphorylation Induced by Lysophosphatidic Acid

• Published in: The Journal of biological chemistry 2003-02, Vol.278 (7), p.4882-4891
• Main Authors: Yuan, J, Slice, L W, Gu, J, Rozengurt, E
• Format: Article
• Language: English
• Subjects: Clostridium difficile
• ISSN: 0021-9258
• DOI: 10.1074/jbc.M211175200

To examine the contribution of different G-protein pathways to lysophosphatidic acid (LPA)-induced protein kinase D (PKD) activation, we tested the effect of LPA on PKD activity in murine embryonic cell lines deficient in Ga sub(q/11) (Ga sub(q/11) KO cells) or Ga sub(12/13) (Ga sub(12/13) KO cells) and used cells lacking rhodopsin kinase (RK cells) as a control. In RK and Ga sub(12/13) KO cells, LPA induced PKD activation through a phospholipase C/protein kinase C pathway in a concentration-dependent fashion with maximal stimulation (6-fold for RK cells and 4-fold for Ga sub(12/13) KO cells in autophosphorylation activity) achieved at 3 kM. In contrast, LPA did not induce any significant increase in PKD activity in Ga sub(q/11) KO cells. However, LPA induced a significantly increased PKD activity when Ga sub(q/11) KO cells were transfected with Ga sub(q). LPA-induced PKD activation was modestly attenuated by prior exposure of RK cells to pertussis toxin (PTx) but abolished by the combination treatments of PTx and Clostridium difficile toxin B. Surprisingly, PTx alone strikingly inhibited LPA-induced PKD activation in a concentration-dependent fashion in Ga sub(12/13) KO cells. Similar results were obtained when activation loop phosphorylation at Ser-744 was determined using an antibody that detects the phosphorylated state of this residue. Our results indicate that G sub(q) is necessary but not sufficient to mediate LPA- induced PKD activation. In addition to G sub(q), LPA requires additional G-protein pathways to elicit a maximal response with G sub(i) playing a critical role in Ga sub(12/13) KO cells. We conclude that LPA induces PKD activation through G sub(q), G sub(i), and G sub(12) and propose that PKD activation is a point of convergence in the action of multiple G-protein pathways.