Angiotensin II-induced extracellular signal-regulated kinase 1/2 activation is mediated by protein kinase Cdelta and intracellular calcium in adult rat cardiac fibroblasts.
Angiotensin II (Ang II)-induced proliferation of cardiac fibroblasts is a major contributing factor to the pathogenesis of cardiac fibrosis. Ang II activates extracellular signal-regulated kinase (ERK) 1/2 to induce cardiac fibroblast proliferation, but the signaling pathways leading to ERK 1/2 activation have not been elucidated in these cells. The goal of the current study was to identify the intracellular mediators of Ang II-induced ERK 1/2 activation in adult rat cardiac fibroblasts. We determined that 100 nmol/L of Ang II-induced ERK 1/2 phosphorylation is inhibited by simultaneous chelation of cytosolic calcium and downregulation of protein kinase C (PKC) by phorbol ester or by the specific PKCdelta inhibitor rottlerin, as well as PKCdelta small interfering RNA, but not by inhibition of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate, phorbol ester, rottlerin, or PKCdelta small interfering RNA alone. We also found that Ang II does not transactivate the epidermal growth factor receptor in adult cardiac fibroblasts, because pretreatment with 1 mumol/L of AG 1478 did not significantly inhibit [(3)H]-thymidine incorporation or ERK 1/2 activation. In addition, immunoprecipitation of the epidermal growth factor receptor demonstrated no significant Ang II-induced phosphorylation of tyrosine residues. Inhibition of phosphatidylinositide 3-kinase, PKCzeta, and src tyrosine kinase had no effect on Ang II-induced ERK 1/2 activation. Collectively, these data demonstrate that Ang II does not transactivate the epidermal growth factor receptor in adult rat cardiac fibroblasts to activate ERK 1/2, a common pathway described in vascular smooth muscle and other cell types, but rather occurs via activation of distinct parallel signaling pathways mechanistically controlled by intracellular Ca(2+) and PKCdelta.
Olson
Erik R
ER
Department of Physiology and Pharmacology, Northeastern Ohio Universities College of Medicine, Rootstown, OH 44272-0095, USA.
Shamhart
Patricia E
PE
Naugle
Jennifer E
JE
Meszaros
J Gary
JG
D000098:Acetophenones / Q000494:pharmacology; D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D001578:Benzopyrans / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology
D000098:Acetophenones; D001578:Benzopyrans; D010703:Phorbol Esters; D000804:Angiotensin II; C085746:rottlerin; C483803:Egfr protein, rat; D066246:ErbB Receptors; D051745:Protein Kinase C-delta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D002118:Calcium