Caveolin-1 abrogates TGF-β mediated hepatocyte apoptosis

Cell Death Dis. 2013 Jan 17;4(1):e466. doi: 10.1038/cddis.2012.204.

Abstract

Transforming growth factor (TGF)-β has a dual role in liver, providing cytostatic effects during liver damage and regeneration, as well as carcinogenic functions in malignant transformation and hepatocellular cancer. In cultured hepatocytes, TGF-β can trigger apoptosis and epithelial-mesenchymal transition (EMT). Caveolin-1 is associated with progression of hepatocellular cancer and has been linked to TGF-β signaling. This study aimed at elucidating whether Caveolin-1 regulates TGF-β mediated hepatocyte fate. Knockdown of Caveolin-1 strongly reduced TGF-β mediated AKT phosphorylation, thus sensitized primary murine hepatocytes for proapoptotic TGF-β signaling. Restoration of AKT activity in Caveolin-1 knockdown cells via expression of a constitutive active AKT mutant did not completely blunt the apoptotic response to TGF-β, indicating an additional mechanism how Caveolin-1 primes hepatocytes for resistance to TGF-β triggered apoptosis. On the molecular level, Caveolin-1 interfered with TGF-β initiated expression of the proapoptotic mediator BIM. Additionally, RNAi for Caveolin-1 reduced (and its overexpression increased) expression of antiapoptotic mediators BCL-2 and BCL-xl. Noteworthy, reduced Caveolin-1 protein levels had no effect on collagen 1α1, E- and N-cadherin expression upon TGF-β challenge and thus no effect on hepatocyte EMT. Hence, via affecting TGF-β mediated non-Smad AKT signaling and regulation of pro- and antiapoptotic factors, Caveolin-1 is a crucial hepatocyte fate determinant for TGF-β effects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / metabolism
  • Bcl-2-Like Protein 11
  • Cadherins / metabolism
  • Caveolin 1 / antagonists & inhibitors
  • Caveolin 1 / genetics
  • Caveolin 1 / metabolism*
  • Cells, Cultured
  • Collagen Type I / metabolism
  • Epithelial-Mesenchymal Transition / drug effects
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism
  • Male
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Phosphorylation
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA Interference
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / metabolism
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / genetics
  • Recombinant Proteins / pharmacology
  • Signal Transduction / drug effects
  • Smad3 Protein / metabolism
  • Transforming Growth Factor beta1 / genetics
  • Transforming Growth Factor beta1 / metabolism
  • Transforming Growth Factor beta1 / pharmacology*
  • bcl-X Protein / metabolism

Substances

  • Apoptosis Regulatory Proteins
  • Bcl-2-Like Protein 11
  • Bcl2l11 protein, mouse
  • Cadherins
  • Caveolin 1
  • Collagen Type I
  • Membrane Proteins
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • RNA, Small Interfering
  • Recombinant Proteins
  • Smad3 Protein
  • Transforming Growth Factor beta1
  • bcl-X Protein
  • Proto-Oncogene Proteins c-akt