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TGF-beta concentration specifies differential signaling profiles of growth arrest/differentiation and apoptosis in

Dona T Wu1, Markus Bitzer, Wenjun Ju

  • 1Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York, USA.

Journal of the American Society of Nephrology : JASN
|October 7, 2005
PubMed

Insights

Transforming growth factor-beta2 (TGF-beta2) promotes podocyte differentiation and growth arrest via Smad3 signaling. Higher TGF-beta levels trigger apoptosis by activating p38 MAPK and inhibiting cell cycle regulators.

Area of Science:

  • Nephrology
  • Cell Biology
  • Molecular Biology

Background:

  • Podocyte depletion is a hallmark of progressive glomerular diseases, driven by impaired proliferation.
  • The role of transforming growth factor-beta (TGF-beta) in podocyte cell cycle control and apoptosis is not fully understood.
  • TGF-beta signaling specificity in cell cycle arrest and apoptosis requires further elucidation.

Purpose of the Study:

  • To investigate the mechanisms of podocyte growth arrest, differentiation, and depletion.
  • To determine the role of TGF-beta isoforms and concentrations in regulating podocyte cell fate.
  • To identify the specific signaling pathways involved in TGF-beta-mediated podocyte responses.

Main Methods:

  • Utilized conditionally immortalized podocytes for in vitro studies.
  • Investigated TGF-beta signaling pathways, including Smad3 and p38 mitogen-activated protein kinase (MAPK).
  • Analyzed the expression of cyclin-dependent kinase inhibitor p15(Ink4b) (Cdkn2b) and apoptosis markers.

Main Results:

  • Autocrine TGF-beta2 signaling induced G0/G1 arrest and differentiation via Smad3 and Cdkn2b.
  • Recombinant TGF-beta1 or TGF-beta2 at higher concentrations induced G2/M arrest and apoptosis.
  • Apoptosis was associated with p38 MAPK activation and Cdkn2b suppression.

Conclusions:

  • TGF-beta2 plays a crucial role in murine podocyte growth arrest and differentiation in vitro.
  • A critical TGF-beta concentration threshold acts as a molecular switch, promoting pro-apoptotic signaling.
  • Understanding these TGF-beta-mediated pathways is vital for addressing podocyte loss in kidney diseases.

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