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Caveolin-2 is a negative regulator of anti-proliferative function and signaling of transforming growth factor-β in

Leike Xie1, Chi Vo-Ransdell, Britain Abel

  • 1Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65212, USA.

American Journal of Physiology. Cell Physiology
|August 12, 2011
PubMed

Insights

Caveolin-2 (Cav-2) negatively regulates the anti-proliferative effects of transforming growth factor-beta (TGF-β) in endothelial cells. Loss of Cav-2 enhances TGF-β signaling, while its reexpression diminishes this response.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Transforming growth factor-beta (TGF-β) is a key regulator of cell proliferation and signaling.
  • Caveolins, including caveolin-2 (Cav-2), are proteins involved in cellular signaling and membrane dynamics.
  • The precise role of Cav-2 in TGF-β signaling pathways, particularly in endothelial cells, requires further elucidation.

Purpose of the Study:

  • To investigate the role of caveolin-2 (Cav-2) in regulating the anti-proliferative function of transforming growth factor-beta (TGF-β) in endothelial cells (ECs).
  • To elucidate the molecular mechanisms by which Cav-2 influences TGF-β signaling.
  • To determine if Cav-2 affects the localization of TGF-β pathway components.

Main Methods:

  • Utilized wild-type (WT) and Cav-2 knockout endothelial cells (ECs).
  • Employed retroviral reexpression of Cav-2 in knockout ECs.
  • Assessed cell proliferation using MTT assays, cell counting, and bromodeoxyuridine incorporation.
  • Analyzed TGF-β signaling components, including p27, retinoblastoma protein, Alk5, and Smad2/3 phosphorylation.
  • Investigated protein localization in lipid raft/caveolar microdomains via sucrose fractionation gradients.

Main Results:

  • Cav-2 knockout ECs exhibited profoundly inhibited proliferation upon TGF-β treatment compared to WT ECs.
  • Reexpression of Cav-2 in knockout ECs restored the modest anti-proliferative effect of TGF-β.
  • Cav-2 suppressed TGF-β-induced upregulation of p27 and hyperphosphorylated retinoblastoma protein.
  • Cav-2 inhibited the Alk5-Smad2/3 pathway, reducing Smad2/3 phosphorylation and target gene activation.
  • Cav-2 expression did not significantly alter the targeting of TGF-β receptors or Smad2/3 to caveolae/lipid rafts.

Conclusions:

  • Caveolin-2 plays a negative regulatory role in the anti-proliferative function and signaling of TGF-β in endothelial cells.
  • Cav-2 inhibits TGF-β's anti-proliferative action by suppressing the Alk5-Smad2/3 pathway.
  • This regulation by Cav-2 is independent of Cav-1 expression and does not involve altered localization of key signaling molecules to lipid rafts.

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