title: ERK1/2 signaling dominates over RhoA signaling in regulating early changes in RNA expression induced by endothelin-1 in neonatal rat cardiomyocytes.
abstract: BACKGROUND
  Cardiomyocyte hypertrophy is associated with changes in gene expression. Extracellular signal-regulated kinases 1/2 (ERK1/2) and RhoA [activated by hypertrophic agonists (e.g. endothelin-1)] regulate gene expression and are implicated in the response, but their relative significance in regulating the cardiomyocyte transcriptome is unknown. Our aim was to establish the significance of ERK1/2 and/or RhoA in the early cardiomyocyte transcriptomic response to endothelin-1.
  
  
  RESULTS
  Cardiomyocytes were exposed to endothelin-1 (1 h) with/without PD184352 (to inhibit ERK1/2) or C3 transferase (C3T, to inhibit RhoA). RNA expression was analyzed using microarrays and qPCR. ERK1/2 signaling positively regulated approximately 65% of the early gene expression response to ET-1 with a small (approximately 2%) negative effect, whereas RhoA signaling positively regulated approximately 10% of the early gene expression response to ET-1 with a greater (approximately 14%) negative contribution. Of RNAs non-responsive to endothelin-1, 66 or 448 were regulated by PD184352 or C3T, respectively, indicating that RhoA had a more significant effect on baseline RNA expression. mRNAs upregulated by endothelin-1 encoded a number of receptor ligands (e.g. Ereg, Areg, Hbegf) and transcription factors (e.g. Abra/Srf) that potentially propagate the response.
  
  
  CONCLUSIONS
  ERK1/2 dominates over RhoA in the early transcriptomic response to endothelin-1. RhoA plays a major role in maintaining baseline RNA expression but, with upregulation of Abra/Srf by endothelin-1, RhoA may regulate changes in RNA expression over longer times. Our data identify ERK1/2 as a more significant node than RhoA in regulating the early stages of cardiomyocyte hypertrophy.
authors.affiliation: National Heart and Lung Institute, Faculty of Medicine, Imperial College London, London, United Kingdom.
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Marshall
authors.forename: Oliver P T
authors.initials: OP
authors.lastname: Barrett
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Cullingford
authors.forename: Achchuthan
authors.initials: A
authors.lastname: Shanmugasundram
authors.forename: Peter H
authors.initials: PH
authors.lastname: Sugden
authors.forename: Angela
authors.initials: A
authors.lastname: Clerk
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D006984:Hypertrophy; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D015398:Signal Transduction; D013997:Time Factors; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D019332:Endothelin-1; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020742:rhoA GTP-Binding Protein