Lysophosphatidic acid rapidly induces protein kinase D activation through a pertussis toxin-sensitive pathway

Protein kinase D(PKD) is a serine-threonine protein kinase with distinct structuralfeatures and enzymological properties. Herein we demonstrate thatlysophosphatidic acid (LPA) induces rapid PKD activation in mouse Swiss3T3 and Rat-1 cells. LPA induced PKD activation in aconcentration-dependent fashion with maximal stimulation (7.6-fold)achieved at 5 µM. Treatment of Swiss 3T3 cells with the proteinkinase C (PKC) inhibitors GF-I, Ro-31-8220, and Gö-7874completely abrogated PKD activation induced by LPA at concentrationsthat did not inhibit PKD activity when added directly to the in vitrokinase assays. PKD activation induced by LPA was attenuated markedlyand selectively by prior exposure of either Swiss 3T3 or Rat-1 cells topertussis toxin (PTx) in a concentration-dependent manner. In contrast,treatment with the protein tyrosine kinase inhibitor genistein, the MEKinhibitor PD-098059, or the phosphoinositide 3-kinase inhibitorwortmannin did not affect PKD activation in response to LPA. Theseresults provide the first example of PTx-sensitive and PKC-dependentPKD activation and identify a novelG_i-dependent event in the action of LPA.