title: Epidermal growth factor induces Ca(2+) sensitization through Rho-kinase-dependent phosphorylation of myosin phosphatase target subunit 1 in vascular smooth muscle.
abstract: We previously found that the protein tyrosine phosphatase inhibitor orthovanadate evoked a vasoconstrictor effect in rat aortas via Rho-kinase-dependent inactivation of myosin light chain phosphatase (MLCP) downstream of epidermal growth factor (EGF) receptor signaling. To determine whether the direct activation of EGF receptor by EGF also induces Rho-kinase-dependent vasoconstriction, isometric tension changes were measured in rat aortic rings without endothelium. Although EGF did not produce a contractile effect, the Ca(2+)-induced force in Ca(2+)-depleted rings significantly increased after treatment with 100nM EGF, suggesting that EGF induces Ca(2+) sensitization by MLCP inactivation. In addition, EGF induced the activation of Rho-kinase and phosphorylation of myosin phosphatase target subunit 1 (MYPT1) in rat aortic smooth muscle cells (VSMCs). The effects of EGF on Ca(2+) sensitivity in aortas and MYPT1 phosphorylation in VSMCs were blocked by inhibitors of EGF receptor (AG1478), Rho-kinase (Y27632), extracellular signal-regulated kinase 1/2 (Erk1/2; FR180204), and mitogen/extracellular signal-regulated kinase (MEK; PD98059), but not by inhibitors of p38 kinase (SB203580) and c-Jun amino-terminal kinase (AS601245). EGF-induced Erk1/2 phosphorylation was not abrogated by the Rho-kinase inhibitor, suggesting that Rho-kinase-dependent phosphorylation of MYPT1 is downstream of EGF receptor/MEK/Erk1/2 signaling. These results suggest that EGF induces Ca(2+) sensitization in vascular smooth muscle by Rho-kinase-dependent inactivation of MLCP mediated by the EGF receptor/MEK/Erk1/2 pathway.
authors.affiliation: Laboratory of Cardiovascular Pharmacology, Department of Biopharmaceutical Sciences, Kobe Gakuin University, Minatojima 1-1-3, Chuo-ku, Kobe 650-8586, Japan.
authors.forename: Tomoya
authors.initials: T
authors.lastname: Sasahara
authors.affiliation: Laboratory of Cardiovascular Pharmacology, Department of Biopharmaceutical Sciences, Kobe Gakuin University, Minatojima 1-1-3, Chuo-ku, Kobe 650-8586, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Okamoto
authors.affiliation: Laboratory of Cardiovascular Pharmacology, Department of Biopharmaceutical Sciences, Kobe Gakuin University, Minatojima 1-1-3, Chuo-ku, Kobe 650-8586, Japan.
authors.forename: Natsumi
authors.initials: N
authors.lastname: Ohkura
authors.affiliation: Laboratory of Cardiovascular Pharmacology, Department of Biopharmaceutical Sciences, Kobe Gakuin University, Minatojima 1-1-3, Chuo-ku, Kobe 650-8586, Japan.
authors.forename: Asami
authors.initials: A
authors.lastname: Kobe
authors.affiliation: Laboratory of Cardiovascular Pharmacology, Department of Biopharmaceutical Sciences, Kobe Gakuin University, Minatojima 1-1-3, Chuo-ku, Kobe 650-8586, Japan. Electronic address: yayama@pharm.kobegakuin.ac.jp.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Yayama
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology; D002118:Calcium / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D006801:Humans; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D054460:rho-Associated Kinases / Q000378:metabolism*
chemical_list: D047428:Protein Kinase Inhibitors; D004815:Epidermal Growth Factor; D054460:rho-Associated Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1; D002118:Calcium
keywords: Epidermal growth factor; Myosin light chain phosphatase; Myosin phosphatase target subunit 1; Rho-kinase; Smooth muscle; Vasoconstriction