Angiotensin II regulates activation of Bim via Rb/E2F1 during apoptosis: involvement of interaction between AMPKβ1/2 and Cdk4

Am J Physiol Lung Cell Mol Physiol. 2012 Aug 1;303(3):L228-38. doi: 10.1152/ajplung.00087.2012. Epub 2012 Jun 1.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • AMP-Activated Protein Kinases / genetics
  • AMP-Activated Protein Kinases / metabolism*
  • Angiotensin II / genetics
  • Angiotensin II / metabolism*
  • Animals
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Apoptosis*
  • Bcl-2-Like Protein 11
  • Blotting, Western
  • Cattle
  • Cells, Cultured
  • Chromatin Immunoprecipitation
  • Cyclin-Dependent Kinase 4 / genetics
  • Cyclin-Dependent Kinase 4 / metabolism*
  • E2F1 Transcription Factor / genetics
  • E2F1 Transcription Factor / metabolism*
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / metabolism
  • Humans
  • Immunoprecipitation
  • Luciferases / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic / genetics
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism
  • Pulmonary Artery / cytology
  • Pulmonary Artery / metabolism
  • Retinoblastoma Protein / genetics
  • Retinoblastoma Protein / metabolism*
  • Signal Transduction
  • Transcriptional Activation
  • bcl-2-Associated X Protein
  • bcl-X Protein

Substances

  • Apoptosis Regulatory Proteins
  • BCL2L11 protein, human
  • Bcl-2-Like Protein 11
  • E2F1 Transcription Factor
  • Membrane Proteins
  • Proto-Oncogene Proteins
  • Retinoblastoma Protein
  • bcl-2-Associated X Protein
  • bcl-X Protein
  • Angiotensin II
  • Luciferases
  • Cyclin-Dependent Kinase 4
  • AMP-Activated Protein Kinases