title: Role of EGF Receptor and Pyk2 in endothelin-1-induced ERK activation in rat cardiomyocytes.
abstract: G protein-coupled receptor (GPCR)-evoked signal transduction pathways leading to the activation of extracellular signal-regulated kinases (ERK) are quite different among cell types. In cardiomyocytes, much attention has been focused on the activation of protein kinase C (PKC) or mobilization of intracellular Ca(2+) ([Ca(2+)](i)), however, the contributions of tyrosine kinases are controversial. In the present study, we characterized the signaling pathways involving tyrosine kinases, Pyk2 and epidermal growth factor receptor (EGFR), and their contribution to ERK activation in cultured cardiomyocytes. We initially investigated the potential involvement of [Ca(2+)](i) and PKC on the activation of these kinases in endothelin-stimulated cardiomyocytes. Interestingly, activation of Pyk2 was abrogated by chelating [Ca(2+)](i) or by downregulation of PKC, whereas transactivation of EGFR was solely dependent on PKC. By using a compound that selectively interferes with EGFR (AG1478), c-Src (PP1), or disrupts actin cytoskeleton (cytochalasin D), we demonstrated that cytochalasin D completely inhibited the activation of Pyk2, but not that of EGFR, whereas AG1478 did not inhibit the activation of Pyk2, indicating that transactivation of EGFR and signaling pathways involving Pyk2 were distinct pathways. Furthermore, activation of ERK and Shc, and c- fos gene expression were significantly inhibited by AG1478 but not by cytochalasin D or PP1. Overexpression of deletion mutant of EGFR attenuated the activation of ERK. These facts demonstrated the existence of two distinct tyrosine kinase pathways requiring Pyk2 or EGFR downstream from GPCR in cardiomyocytes. EGFR was Ca(2+)-independently activated and predominantly contributed to Shc/ERK/c- fos activation, while Pyk2 or c-Src contributed less to it.
authors.affiliation: Cardiopulmonary Division, Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kodama
authors.forename: Keiichi
authors.initials: K
authors.lastname: Fukuda
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takahashi
authors.forename: Motoaki
authors.initials: M
authors.lastname: Sano
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kato
authors.forename: Satoko
authors.initials: S
authors.lastname: Tahara
authors.forename: Daihiko
authors.initials: D
authors.lastname: Hakuno
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Sato
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Manabe
authors.forename: Fusako
authors.initials: F
authors.lastname: Konishi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ogawa
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology; D000199:Actins / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000502:physiology; D066246:ErbB Receptors / Q000502:physiology*; D051418:Focal Adhesion Kinase 2; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008666:Metalloendopeptidases / Q000502:physiology; D009206:Myocardium / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013234:Stem Cells / Q000378:metabolism
chemical_list: D000199:Actins; D019332:Endothelin-1; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; C496054:Ptk2b protein, rat; D008666:Metalloendopeptidases; D002118:Calcium