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 journalArticle

15 Citations (Scopus)

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 - Jan 1 2004

Fingerprint

Caveolae
Transforming Growth Factors
Smooth Muscle Myocytes
Cholesterol
Growth
Growth Inhibitors
Membranes
Growth Factor Receptors
DNA
Thymidine
Inhibitory Concentration 50

Keywords

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

ASJC Scopus subject areas

  • Urology

Cite this

Caveolae are negative regulators of transforming growth factor-β1 signaling in ureteral smooth muscle cells. / Stehr, Maximilian; Estrada, Carlos R.; Khoury, Joseph; Danciu, Theodora E.; Sullivan, Maryrose P.; Peters, Craig A; Solomon, Keith R.; Freeman, Michael R.; Adam, Rosalyn M.

In: Journal of Urology, Vol. 172, No. 6 I, 01.01.2004, p. 2451-2455.

Research output: Contribution to journalArticle

Stehr, M, Estrada, CR, Khoury, J, Danciu, TE, Sullivan, MP, Peters, CA, Solomon, KR, Freeman, MR & Adam, RM 2004, 'Caveolae are negative regulators of transforming growth factor-β1 signaling in ureteral smooth muscle cells', Journal of Urology, vol. 172, no. 6 I, pp. 2451-2455. https://doi.org/10.1097/01.ju.0000138084.53577.ca
Stehr, Maximilian ; Estrada, Carlos R. ; Khoury, Joseph ; Danciu, Theodora E. ; Sullivan, Maryrose P. ; Peters, Craig A ; Solomon, Keith R. ; Freeman, Michael R. ; Adam, Rosalyn M. / Caveolae are negative regulators of transforming growth factor-β1 signaling in ureteral smooth muscle cells. In: Journal of Urology. 2004 ; Vol. 172, No. 6 I. pp. 2451-2455.
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AU - Estrada, Carlos R.

AU - Khoury, Joseph

AU - Danciu, Theodora E.

AU - Sullivan, Maryrose P.

AU - Peters, Craig A

AU - Solomon, Keith R.

AU - Freeman, Michael R.

AU - Adam, Rosalyn M.

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N2 - 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.

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KW - Caveolae

KW - Membrane microdomains

KW - Smooth muscle

KW - Transforming growth factor beta1

KW - Ureter

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