title: Urotensin II induces rat cardiomyocyte hypertrophy via the transient oxidization of Src homology 2-containing tyrosine phosphatase and transactivation of epidermal growth factor receptor.
abstract: Urotensin II (U-II) is implicated in cardiomyocyte hypertrophy, which results in cardiac remodeling. We recently demonstrated that both reactive oxygen species (ROS) generation and epidermal growth factor receptor (EGFR) transactivation play critical roles in U-II signal transduction. However, the detailed intracellular mechanism(s) underlying cardiac hypertrophy and remodeling remain unclear. In this study, we used rat cardiomyocytes treated with U-II to investigate the association between ROS generation and EGFR transactivation. U-II treatment was found to stimulate cardiomyocyte hypertrophy through phosphorylation of EGFR and ROS generation. Apocynin, an NAD(P)H oxidase inhibitor, and N-acetyl cysteine (NAC), an ROS scavenger, both inhibited EGFR transactivation induced by U-II. In contrast, 4-(3'-chloroanilino)-6,7-dimethoxy-quinazoline (AG1478, an EGFR inhibitor) failed to inhibit intracellular ROS generation induced by U-II. Src homology 2-containing tyrosine phosphatase (SHP-2), but not protein tyrosine phosphatase 1B (PTP 1B), was shown to be associated with EGFR during U-II treatment by EGFR coimmunoprecipitation. ROS have been reported to transiently oxidize the catalytic cysteine of phosphotyrosine phosphatases, subsequently inhibiting their activity. We examined the effect of U-II on SHP-2 and PTP 1B in cardiomyocytes using a modified malachite green phosphatase assay. SHP-2, but not PTP 1B, was transiently oxidized during U-II treatment, which could be repressed by NAC treatment. In SHP-2 knockdown cells, U-II-induced phosphorylation of EGFR and myocyte hypertrophy were dramatically elevated, and these effects were not influenced by NAC. Our data suggest that U-II-mediated ROS generation can transiently inhibit SHP-2 activity, thereby facilitating EGFR transactivation and hypertrophic signal transduction in rat cardiomyocytes.
authors.affiliation: Department of Biological Science and Technology, College of Life Sciences, China Medical University, 91 Hsueh-Shih Road, Taichung, Taiwan 40402, R.O.C.
authors.forename: Ju-Chi
authors.initials: JC
authors.lastname: Liu
authors.forename: Cheng-Hsien
authors.initials: CH
authors.lastname: Chen
authors.forename: Jin-Jer
authors.initials: JJ
authors.lastname: Chen
authors.forename: Tzu-Hurng
authors.initials: TH
authors.lastname: Cheng
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D066246:ErbB Receptors / Q000096:biosynthesis*; D005434:Flow Cytometry; D055785:Gene Knockdown Techniques; D006984:Hypertrophy / Q000139:chemically induced; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D010084:Oxidation-Reduction; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects*; D014579:Urotensins / Q000494:pharmacology*
chemical_list: D017382:Reactive Oxygen Species; D055765:Shc Signaling Adaptor Proteins; D014579:Urotensins; C029677:urotensin II; D066246:ErbB Receptors; D017027:Protein Tyrosine Phosphatases