Epidermal growth factor induction of phenotype-dependent cell cycle arrest in vascular smooth muscle cells is through the mitogen-activated protein kinase pathway.
The heterogeneity of vascular smooth muscle cells is well established in tissue culture, but their differential responses to growth factors are not completely defined. We wished to identify effects of epidermal growth factor (EGF) on vascular smooth muscle cells in distinct phenotypes, such as spindle and epithelioid. We found that the EGF receptors were abundant in epithelioid cells but not spindle cells. EGF treatment inhibited serum-independent DNA synthesis, which was absent in spindle cells, of epithelioid cells. Additionally, using a pulse-chase assay, we found that bromodeoxyuridine-labeled cells failed to re-enter the S phase in the presence of EGF. These EGF effects were abolished by either inhibiting the EGF receptor tyrosine kinase with AG1478 or inhibiting the mitogen-activated protein kinase pathway with PD98059. In response to treatment with EGF, the EGF receptor was phosphorylated, which was correlated with phosphorylation and activation of p42/44 mitogen-activated protein kinases. Inhibition of EGF receptor phosphorylation and mitogen-activated protein kinase activation resulted in a reversal of the EGF-induced inhibition of bromodeoxyuridine incorporation and cell cycle arrest. Subsequent studies revealed that the activation of the EGF receptor and the mitogen-activated protein kinase pathway in epithelioid cells induced expression of the cell cycle inhibitory protein p27Kip1 but not p21Cip1. Taken together, our data demonstrate that the EGF receptor is abundantly expressed in epithelioid vascular smooth muscle cells and that the activation of this receptor results in cell cycle arrest through activation of the mitogen-activated protein kinase pathway.
Gui
Yu
Y
Smooth Muscle Research Group, Department of Biochemistry & Molecular Biology, The University of Calgary, Calgary, Alberta T2N 4N1, Canada.
Zheng
Xi-Long
XL
D000818:Animals; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D004396:Coloring Agents / Q000494:pharmacology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System; D008297:Male; D018613:Microscopy, Confocal; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D010641:Phenotype; D010766:Phosphorylation; D011799:Quinazolines; D051381:Rats; D017207:Rats, Sprague-Dawley; D016196:S Phase; D013997:Time Factors; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology
C493956:CDKN1A protein, human; C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D004396:Coloring Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D011799:Quinazolines; D025521:Tumor Suppressor Proteins; D020032:Tyrphostins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C101044:RTKI cpd; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D001973:Bromodeoxyuridine; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one