title: Phosphatidylinositol 3-kinase regulates bone morphogenetic protein-2 (BMP-2)-induced myocyte enhancer factor 2A-dependent transcription of BMP-2 gene in cardiomyocyte precursor cells.
abstract: The growth and differentiation factor bone morphogenetic protein-2 (BMP-2) regulates cardiac development during vertebrate embryogenesis. In cardiac precursor cells, BMP-2 has recently been shown to induce expression of cardiac transcription factors, including myocyte enhancer factor 2A (MEF-2A). The specific signal transduction mechanism by which BMP-2 regulates these actions is not known. We investigated the role of phosphatidylinositol (PI) 3-kinase in regulating these processes in cardiomyocyte precursor CL6 cells. BMP-2 increased PI 3-kinase activity in these cells in a time-dependent manner, resulting in increased expression of sarcomeric myosin heavy chain (MHC) and MEF-2A. Inhibition of PI 3-kinase abolished these actions of BMP-2, indicating the involvement of PI 3-kinase in these processes. Furthermore, BMP-2 stimulated specific protein.DNA complex formation when an MEF-2 DNA recognition element was used as probe. Antibody supershift assay confirmed the presence of MEF-2A in this protein.DNA complex. Inhibition of PI 3-kinase activity completely prevented the MEF-2A.DNA complex formation. BMP-2 also increased transcription of a reporter gene driven by an MEF-2-specific DNA element in a PI 3-kinase-dependent manner. Ectopic expression of MEF-2A increased BMP-2 transcription to the same extent induced by BMP-2, indicating that MEF-2A may participate in BMP-2 autoregulation in CL6 cells. Expression of dominant negative PI 3-kinase completely abolished BMP-2-induced as well as MEF-2A-mediated BMP-2 transcription. Furthermore expression of MEF-2A increased MHC expression in a PI 3-kinase-dependent manner. Together these data provide the first evidence that BMP-2-induced PI 3-kinase signaling regulates MEF-2A expression and define a mechanism of MEF-2A-dependent BMP-2 transcription.
authors.affiliation: Department of Pathology, University of Texas Health Science Center, San Antonio, TX 78229-3900, USA.
authors.forename: Nandini
authors.initials: N
authors.lastname: Ghosh-Choudhury
authors.forename: Sherry L
authors.initials: SL
authors.lastname: Abboud
authors.forename: Lenin
authors.initials: L
authors.lastname: Mahimainathan
authors.forename: Bysani
authors.initials: B
authors.lastname: Chandrasekar
authors.forename: Goutam Ghosh
authors.initials: GG
authors.lastname: Choudhury
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005799:Genes, Dominant; D005822:Genetic Vectors; D015151:Immunoblotting; D008156:Luciferases / Q000378:metabolism; D064326:MEF2 Transcription Factors; D051379:Mice; D008856:Microscopy, Fluorescence; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D018006:Myogenic Regulatory Factors; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D016212:Transforming Growth Factor beta
chemical_list: C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D011994:Recombinant Proteins; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D004247:DNA; D008156:Luciferases; D019869:Phosphatidylinositol 3-Kinases