title: NRG-1-induced cardiomyocyte hypertrophy. Role of PI-3-kinase, p70(S6K), and MEK-MAPK-RSK.
abstract: Neuregulins are a family of growth-promoting peptides known to be important in neural and mesenchymal tissue development. Targeted disruption of neuregulin (NRG)-1 or one of two of its cognate receptors, ErbB2 or ErbB4, results in embryonic lethality because of failure of the heart to develop. Although expression of NRGs and their receptors declines after midembryogenesis, both ErbB2 and ErbB4 are present in cardiac myocytes, and NRG-1 expression remains inducible in primary cultures of coronary microvascular endothelial cells from adult rat ventricular muscle. In neonatal rat ventricular myocytes, a soluble NRG-1, recombinant human glial growth factor-2, increased [(3)H]phenylalanine uptake and induced expression of atrial natriuretic factor (ANF) and sarcomeric F-actin polymerization. The effect of NRG-1 on [(3)H]phenylalanine uptake and sarcomeric F-actin polymerization was maximal at 20 ng/ml but declined at higher concentrations. NRG-1 activated p42/p44 mitogen-activated protein kinase (MAPK) [extracellular signal-regulated kinase (ERK)-2/ERK1] and ribosomal S6 kinase (RSK)-2 (90-kDa ribosomal S6 kinase), both of which could be inhibited by the MAPK/ERK kinase-1 antagonist PD-098059. NRG-1 also activated 70-kDa ribosomal S6 kinase, which was inhibited by either rapamycin or wortmannin. Activation of these pathways exhibited the same "biphasic" response to increasing NRG-1 concentrations. Wortmannin and LY-294002 blocked sarcomeric F-actin polymerization but not [(3)H]phenylalanine uptake or ANF expression, whereas PD-098059 consistently blocked both [(3)H]phenylalanine uptake and ANF expression but not actin polymerization. In contrast, rapamycin inhibited [(3)H]phenylalanine uptake and F-actin polymerization but not ANF expression. Thus NRG-ErbB signaling triggers multiple nonredundant pathways in postnatal ventricular myocytes.
authors.affiliation: Cardiovascular Division, Brigham and Women's Hospital and Harvard Medical School, Boston 02115, Massachusetts. rakelly@rics.bwh.harvard.edu
authors.forename: R R
authors.initials: RR
authors.lastname: Baliga
authors.forename: D R
authors.initials: DR
authors.lastname: Pimental
authors.forename: Y Y
authors.initials: YY
authors.lastname: Zhao
authors.forename: W W
authors.initials: WW
authors.lastname: Simmons
authors.forename: M A
authors.initials: MA
authors.lastname: Marchionni
authors.forename: D B
authors.initials: DB
authors.lastname: Sawyer
authors.forename: R A
authors.initials: RA
authors.lastname: Kelly
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000235:genetics; D006332:Cardiomegaly / Q000139:chemically induced* / Q000473:pathology*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006352:Heart Ventricles; D006801:Humans; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism / Q000502:physiology; D009206:Myocardium / Q000473:pathology*; D020890:Neuregulin-1 / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology; D011498:Protein Precursors / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism / Q000502:physiology; D012518:Sarcomeres / Q000378:metabolism
chemical_list: D000199:Actins; D004791:Enzyme Inhibitors; D020890:Neuregulin-1; D011498:Protein Precursors; D011994:Recombinant Proteins; D009320:Atrial Natriuretic Factor; D019869:Phosphatidylinositol 3-Kinases; D019893:Ribosomal Protein S6 Kinases; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases