ANG II and LPA induce Pyk2 tyrosine phosphorylation in intestinal epithelial cells: role of Ca2+, PKC, and Rho kinase

The G protein-coupled receptor agonistsangiotensin II (ANG II) and lysophosphatidic acid (LPA) rapidly inducetyrosine phosphorylation of the cytosolic proline-rich tyrosine kinase2 (Pyk2) in IEC-18 intestinal epithelial cells. The combined Pyk2tyrosine phosphorylation induced by phorbol 12,13-dibutyrate, a directagonist of protein kinase C (PKC), and ionomycin, a Ca²⁺ionophore, was equal to that induced by ANG II. Inhibition of eitherPKC or Ca²⁺ signaling attenuated the effect of ANG II andLPA, although simultaneous inhibition of both pathways failed tocompletely abolish Pyk2 tyrosine phosphorylation. Cytochalasin D, whichdisrupts stress fibers, strongly inhibited the response of Pyk2 to ANGII or LPA. The distinct Rho-associated kinase (ROK) inhibitors HA-1077and Y-27632, as well as the Rho inhibitor Clostridiumbotulinum C3 exoenzyme, also significantly attenuated ANG II- andLPA-stimulated Pyk2 tyrosine phosphorylation. Simultaneous inhibitionof PKC, Ca²⁺, and either actin assembly or ROK completelyabolished the Pyk2 response. Together, these results show that ANG IIand LPA rapidly induce Pyk2 tyrosine phosphorylation in intestinalepithelial cells via separate Ca²⁺-, PKC-, and Rho-mediated pathways.