We have previously shown that A10 vascular smooth muscle cells (VSMC) exposed to angiotensin II (Ang II) exhibited overexpression of Giα proteins. In the present study, we examined the involvement of different signaling pathways in regulating Ang II induced enhanced expression of Giα proteins in VSMC by using pharmacological inhibitors. Ang II induced increased expression of Giα proteins in A10 VSMC was markedly attenuated by actinomycin D, losartan (an AT1 receptor antagonist), dibutyryl cAMP, phospholipase C (PLC) inhibitor U73122, protein kinase C (PKC) inhibitors staurosporine and GP109203X, but not by PD123319 (an AT2 receptor antagonist). In addition, BAPTA-AM and TMB-8 (chelators of intracellular Ca2+); and nifedipine (a blocker of L-type Ca2+ channels) significantly inhibited Ang II induced enhanced expression of Giα proteins. On the other hand, extracellular Ca2+ chelation using EGTA did not affect the Ang II evoked enhanced levels of Giα proteins. Furthermore, pretreatment of A10 VSMC with calmidazolium (an inhibitor of calmodulin), or KN93 (an inhibitor of CaM kinase), or genistein (an inhibitor of protein tyrosine kinase, PTK), also attenuated the increased levels of Giα proteins induced by Ang II. These results suggest that Ang II induced enhanced expression of Giα proteins may be regulated by different signaling pathways through AT1 receptors in A10 VSMC.
Angiotensin II‐induced migration of vascular smooth muscle cells (VSMCs) is mediated by both 72‐KDa spleen tyrosine kinase (Syk) via p38‐MAPK activated c‐Src and by ERK1/2 via c‐Src‐induced EGFR transactivation
