Involvement of PYK2 in angiotensin II signaling of vascular smooth muscle cells

PYK2, a recently identified Ca2+-sensitive tyrosine kinase, has been implic ated in extracellular signal-regulated kinase (ERK) activation via several G protein-coupled receptors. We have reported that angiotensin II (Ang II) induces Ca2+-dependent transactivation of the epidermal growth factor recep tor (EGFR) which serves as a scaffold for preactivated c-Src and downstream adaptors (Shc/Grb2), leading to ERK activation in cultured rat vascular sm ooth muscle cells (VSMC). Herein we demonstrate the involvement of PYK2 in this cascade. Ang II rapidly induced tyrosine phosphorylation of PYK2, whos e effect was completely inhibited by an AT(1) receptor antagonist and an in tracellular Ca2+ chelator, A Ca2+ ionophore also induced PYK2 tyrosine phos phorylation to a level comparable with that by Ang II, whereas phorbol este r-induced phosphorylation was less than that by Ang II. Moreover, PYK2 form ed a complex coprecipitable with catalytically active c-Src after Ang II st imulation. Although a selective EGFR kinase inhibitor completely abolished Ang II-induced recruitment of Grb2 to EGFR and markedly attenuated Ang II-i nduced ERK activation, it had no effect on Ang II-induced PYK2 tyrosine pho sphorylation or its association with c-Src and Grb2. These data suggest tha t the AT(1) receptor uses Ca2+-dependent PYK2 to activate c-Src, thereby le ading to EGFR transactivation, which preponderantly recruits Grb2 in rat VS MC.