Angiotensin II regulates activation of Bim via Rb/E2F1 during apoptosis: involvement of interaction between AMPKβ1/2 and Cdk4.
Apoptotic cell death is essential for mammalian development and tissue homeostasis. Dysregulation of apoptosis has been identified in pathologies including in pulmonary fibrotic remodeling. We previously reported that a key proapoptotic factor in fibrosis, angiotensin II (Ang II), mediates apoptosis in primary pulmonary artery endothelial cells (PAEC) via the AT(2) receptor and requires activation of AMP-regulated protein kinase (AMPK). We now demonstrate that Ang II induces E2F1 transcription factor binding to and activation of the promoter for the Bcl-2 homology 3 (BH3)-only protein Bim. In PAEC, Ang II treatment induced cyclin-dependent kinase 4 (Cdk4)-mediated hyperphosphorylation of retinoblastoma protein (Rb) and its disassociation from E2F1, a key step in facilitating E2F1-directed transcriptional activity. Indeed, ectopic expression of a dominant negative Cdk4 mutant inhibited Ang II-mediated hyperphosphorylation of Rb and Bim promoter activation. Our data also show that the β-subunit of AMPK was constitutively associated with Cdk4 in PAEC and that Ang II treatment induced AMPKβ phosphorylation and subsequent disassociation of this complex. Both Ang II-induced Rb hyperphosphorylation and Cdk4-AMPK disassociation were blocked by the AMPK inhibitor compound C. Together these findings illuminate a novel proapoptotic signaling pathway in endothelial cells, whereby Ang II triggers E2F1-mediated transcriptional upregulation of Bim via activation of AMPKβ1/2 and Cdk4.
Department of Pharmacology, Uniformed Services University of Health Sciences, Bethesda, Maryland 20814-4799, USA.
Yong-Chul
YC
Kim
Regina M
RM
Day
D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000804:Angiotensin II / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D015153:Blotting, Western; D002417:Cattle; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D051358:Cyclin-Dependent Kinase 4 / Q000235:genetics / Q000378:metabolism*; D050687:E2F1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015533:Transcriptional Activation; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D050687:E2F1 Transcription Factor; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D000804:Angiotensin II; D008156:Luciferases; D051358:Cyclin-Dependent Kinase 4; D055372:AMP-Activated Protein Kinases