Caveolae are negative regulators of transforming growth factor-β1 signaling in ureteral smooth muscle cells

Maximilian Stehr, Carlos R. Estrada, Joseph Khoury, Theodora E. Danciu, Maryrose P. Sullivan, Craig A Peters, Keith R. Solomon, Michael R. Freeman, Rosalyn M. Adam

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Purpose: The mechanisms underlying ureteral cell regulation are largely unknown. Previous studies have identified lipid rafts/caveolae as regulators of growth stimulatory signals in ureteral smooth muscle cells (USMCs). In this study we determined whether growth inhibitory signaling by transforming growth factor-β1 (TGF-β1) is also regulated by caveolae in USMC. Materials and Methods: Expression of components of the TGF-β1 signaling axis in USMCs was determined by immunoblot and mRNA analyses. Growth regulatory activity of TGF-β1 was assessed by 3H-thymidine incorporation. In select experiments caveolae were disrupted reversibly by cholesterol depletion and replenishment prior to TGF-β1 treatment. TGF-β1-responsive gene expression was evaluated using the TGF-β1 responsive promoter-reporter construct 3TP-Lux. Results: USMCs expressed TGF-β1, types I and II TGF-β1 receptors, and the effector Smad-2. TGF-β1 potently inhibited DNA synthesis in USMCs (IC50 60 pM). TGF-β1 mediated DNA synthesis inhibition was potentiated following the disruption of caveolae by cholesterol depletion. This effect was reversible with membrane cholesterol restoration. TGF-β1 stimulated gene activity was augmented by caveolae disruption, while caveolae reformation returned promoter activity to baseline levels. Conclusions: TGF-β1 is a potent growth inhibitor of USMCs and its activity can be enhanced by caveolae ablation. These findings suggest a role for TGF-β1 in the growth regulation of normal ureteral cells and implicate caveolar membrane domains in the negative regulation of TGF-β1 signaling. These studies may be relevant to ureteral pathologies that are characterized by smooth muscle dysplasia.

Original languageEnglish (US)
Pages (from-to)2451-2455
Number of pages5
JournalJournal of Urology
Volume172
Issue number6 I
DOIs
StatePublished - Dec 2004

Keywords

  • Caveolae
  • Membrane microdomains
  • Smooth muscle
  • Transforming growth factor beta1
  • Ureter

ASJC Scopus subject areas

  • Urology

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