title: Inhibition of hypoxia-induced apoptosis by modulation of retinoblastoma protein-dependent signaling in cardiomyocytes.
abstract: Apoptotic cell death is an important mode of cell loss contributing to heart dysfunction. To analyze the importance of the E2F-dependent regulation of gene transcription in cardiomyocyte apoptosis, the function of cell cycle factors impinging on the retinoblastoma protein (pRb)/E2F pathway was investigated. In isolated neonatal ventricular myocytes, apoptotic cell death induced by hypoxia (deferoxamine, 100 micro mol/L) specifically activated cyclin-dependent kinases (cdks) 2 and 3. Apoptotic cell death was inhibited by ectopic expression of cdk inhibitors p21(CIP) and p27(KIP1) but not p16(INK4). In addition, apoptosis was also abrogated by forced expression of kinase dead mutant proteins of cdk2/3 but not of cdk4/6. Introduction of cdk inhibitors or dominant-negative cdk2/3 blocked pRb hyperphosphorylation and abrogated E2F-dependent gene transcription, including that of the E2F-responsive genes of proapoptotic caspase 3 and caspase 7. Moreover, introduction of constitutively active pRb and transcriptionally inert mutant E2F1/DP1 efficiently protected cardiomyocytes from apoptosis. In conclusion, these data demonstrate that cdk-specific inactivation of pRb and the subsequent activation of E2F-dependent gene transcription are required for cardiomyocyte apoptosis.
authors.affiliation: Department of Cardiology, Campus Virchow Clinic, Charité, Humboldt University, and the Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
authors.forename: Ludger
authors.initials: L
authors.lastname: Hauck
authors.forename: Georg
authors.initials: G
authors.lastname: Hansmann
authors.forename: Rainer
authors.initials: R
authors.lastname: Dietz
authors.forename: Rüdiger
authors.initials: R
authors.lastname: von Harsdorf
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017930:Genes, Reporter; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C493958:Cdkn1a protein, rat; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493755:E2f1 protein, rat; D004791:Enzyme Inhibitors; D016160:Retinoblastoma Protein; D050680:Transcription Factor DP1; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases; D020169:Caspases