Limits...
Tumor suppressor PTEN inhibits nuclear accumulation of beta-catenin and T cell/lymphoid enhancer factor 1-mediated transcriptional activation.

Persad S, Troussard AA, McPhee TR, Mulholland DJ, Dedhar S - J. Cell Biol. (2001)

Bottom Line: We show that nuclear beta-catenin expression is constitutively elevated in PTEN cells and this elevated expression is reduced upon reexpression of PTEN.TCF promoter/luciferase reporter assays and gel mobility shift analysis demonstrate that PTEN also suppresses TCF transcriptional activity.Our data indicate that beta-catenin/TCF-mediated gene transcription is regulated by PTEN, and this may represent a key mechanism by which PTEN suppresses tumor progression.

View Article: PubMed Central - PubMed

Affiliation: British Columbia Cancer Agency, Jack Bell Research Center, Vancouver V6H 3Z6, British Columbia, Canada.

ABSTRACT
beta-Catenin is a protein that plays a role in intercellular adhesion as well as in the regulation of gene expression. The latter role of beta-catenin is associated with its oncogenic properties due to the loss of expression or inactivation of the tumor suppressor adenomatous polyposis coli (APC) or mutations in beta-catenin itself. We now demonstrate that another tumor suppressor, PTEN, is also involved in the regulation of nuclear beta-catenin accumulation and T cell factor (TCF) transcriptional activation in an APC-independent manner. We show that nuclear beta-catenin expression is constitutively elevated in PTEN cells and this elevated expression is reduced upon reexpression of PTEN. TCF promoter/luciferase reporter assays and gel mobility shift analysis demonstrate that PTEN also suppresses TCF transcriptional activity. Furthermore, the constitutively elevated expression of cyclin D1, a beta-catenin/TCF-regulated gene, is also suppressed upon reexpression of PTEN. Mechanistically, PTEN increases the phosphorylation of beta-catenin and enhances its rate of degradation. We define a pathway that involves mainly integrin-linked kinase and glycogen synthase kinase 3 in the PTEN-dependent regulation of beta-catenin stability, nuclear beta-catenin expression, and transcriptional activity. Our data indicate that beta-catenin/TCF-mediated gene transcription is regulated by PTEN, and this may represent a key mechanism by which PTEN suppresses tumor progression.

Show MeSH

Related in: MedlinePlus

Expression of nuclear β-catenin is reduced by reexpression of PTEN in PTEN  prostate cancer cells. (A) Immunofluorescence analysis of PTEN  prostate cancer cells, PC3, shows that a significant population (70%) of these cells express high levels of β-catenin in their nucleus (arrowheads). Reexpression of PTEN in PTEN  prostate cancer cells LNCaP (B) and PC3 (C) results in a dose-dependent reduction in the expression of nuclear β-catenin. (D) Immunofluorescence analysis of β-catenin confirms that unlike nontransfected PC3 cells (arrowheads), PC3 cells transfected with PTEN (arrows) exhibit anuclear localization β-catenin. A significantly lower proportion of cells in this case express high levels of nuclear β-catenin (16%). Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2192018&req=5

Figure 1: Expression of nuclear β-catenin is reduced by reexpression of PTEN in PTEN prostate cancer cells. (A) Immunofluorescence analysis of PTEN prostate cancer cells, PC3, shows that a significant population (70%) of these cells express high levels of β-catenin in their nucleus (arrowheads). Reexpression of PTEN in PTEN prostate cancer cells LNCaP (B) and PC3 (C) results in a dose-dependent reduction in the expression of nuclear β-catenin. (D) Immunofluorescence analysis of β-catenin confirms that unlike nontransfected PC3 cells (arrowheads), PC3 cells transfected with PTEN (arrows) exhibit anuclear localization β-catenin. A significantly lower proportion of cells in this case express high levels of nuclear β-catenin (16%). Bar, 5 μm.

Mentions: Upon examination of β-catenin expression in prostate cancer cell lines, we noted that a significant population of the PTEN-negative prostate cancer cells (PC3; ∼70%) express high levels of β-catenin in the nucleus (Fig. 1 A). Constitutively high levels of β-catenin are also observed in nuclear extracts from PC3 cells as well as another PTEN prostate cancer cell line, LNCaP (Fig. 1b and Fig. c). Transient transfection of increasing amounts of PTEN-WT into these PTEN cells (LNCaP and PC3) leads to inhibition of nuclear β-catenin expression in these cells (Fig. 1b and Fig. c). The transfection efficiency of the PTEN-WT plasmid is ∼80% in PC3 and LNCaP prostate cancer cells. There was no change in nuclear β-catenin expression when PC3 cells were transfected with increasing amounts of pEGFP cDNA (Fig. 1 C). Total cellular β-catenin expression was unaffected by the PTEN transfections. Immunofluorescence microscopy of PC3 cells transiently transfected with PTEN-GFP also showed that β-catenin is mostly present outside the nucleus in cells expressing PTEN-GFP, and a much smaller number of cells (∼16%) express nuclear β-catenin (Fig. 1 D). Surprisingly, reexpression of PTEN also induced the expression of E-cadherin in PC3 cells, which do not normally express E-cadherin (Fig. 1 C). However, PC3 cells do express N-cadherin and the expression of this cadherin remains unchanged by the reexpression of PTEN (Fig. 1 C).


Tumor suppressor PTEN inhibits nuclear accumulation of beta-catenin and T cell/lymphoid enhancer factor 1-mediated transcriptional activation.

Persad S, Troussard AA, McPhee TR, Mulholland DJ, Dedhar S - J. Cell Biol. (2001)

Expression of nuclear β-catenin is reduced by reexpression of PTEN in PTEN  prostate cancer cells. (A) Immunofluorescence analysis of PTEN  prostate cancer cells, PC3, shows that a significant population (70%) of these cells express high levels of β-catenin in their nucleus (arrowheads). Reexpression of PTEN in PTEN  prostate cancer cells LNCaP (B) and PC3 (C) results in a dose-dependent reduction in the expression of nuclear β-catenin. (D) Immunofluorescence analysis of β-catenin confirms that unlike nontransfected PC3 cells (arrowheads), PC3 cells transfected with PTEN (arrows) exhibit anuclear localization β-catenin. A significantly lower proportion of cells in this case express high levels of nuclear β-catenin (16%). Bar, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2192018&req=5

Figure 1: Expression of nuclear β-catenin is reduced by reexpression of PTEN in PTEN prostate cancer cells. (A) Immunofluorescence analysis of PTEN prostate cancer cells, PC3, shows that a significant population (70%) of these cells express high levels of β-catenin in their nucleus (arrowheads). Reexpression of PTEN in PTEN prostate cancer cells LNCaP (B) and PC3 (C) results in a dose-dependent reduction in the expression of nuclear β-catenin. (D) Immunofluorescence analysis of β-catenin confirms that unlike nontransfected PC3 cells (arrowheads), PC3 cells transfected with PTEN (arrows) exhibit anuclear localization β-catenin. A significantly lower proportion of cells in this case express high levels of nuclear β-catenin (16%). Bar, 5 μm.
Mentions: Upon examination of β-catenin expression in prostate cancer cell lines, we noted that a significant population of the PTEN-negative prostate cancer cells (PC3; ∼70%) express high levels of β-catenin in the nucleus (Fig. 1 A). Constitutively high levels of β-catenin are also observed in nuclear extracts from PC3 cells as well as another PTEN prostate cancer cell line, LNCaP (Fig. 1b and Fig. c). Transient transfection of increasing amounts of PTEN-WT into these PTEN cells (LNCaP and PC3) leads to inhibition of nuclear β-catenin expression in these cells (Fig. 1b and Fig. c). The transfection efficiency of the PTEN-WT plasmid is ∼80% in PC3 and LNCaP prostate cancer cells. There was no change in nuclear β-catenin expression when PC3 cells were transfected with increasing amounts of pEGFP cDNA (Fig. 1 C). Total cellular β-catenin expression was unaffected by the PTEN transfections. Immunofluorescence microscopy of PC3 cells transiently transfected with PTEN-GFP also showed that β-catenin is mostly present outside the nucleus in cells expressing PTEN-GFP, and a much smaller number of cells (∼16%) express nuclear β-catenin (Fig. 1 D). Surprisingly, reexpression of PTEN also induced the expression of E-cadherin in PC3 cells, which do not normally express E-cadherin (Fig. 1 C). However, PC3 cells do express N-cadherin and the expression of this cadherin remains unchanged by the reexpression of PTEN (Fig. 1 C).

Bottom Line: We show that nuclear beta-catenin expression is constitutively elevated in PTEN cells and this elevated expression is reduced upon reexpression of PTEN.TCF promoter/luciferase reporter assays and gel mobility shift analysis demonstrate that PTEN also suppresses TCF transcriptional activity.Our data indicate that beta-catenin/TCF-mediated gene transcription is regulated by PTEN, and this may represent a key mechanism by which PTEN suppresses tumor progression.

View Article: PubMed Central - PubMed

Affiliation: British Columbia Cancer Agency, Jack Bell Research Center, Vancouver V6H 3Z6, British Columbia, Canada.

ABSTRACT
beta-Catenin is a protein that plays a role in intercellular adhesion as well as in the regulation of gene expression. The latter role of beta-catenin is associated with its oncogenic properties due to the loss of expression or inactivation of the tumor suppressor adenomatous polyposis coli (APC) or mutations in beta-catenin itself. We now demonstrate that another tumor suppressor, PTEN, is also involved in the regulation of nuclear beta-catenin accumulation and T cell factor (TCF) transcriptional activation in an APC-independent manner. We show that nuclear beta-catenin expression is constitutively elevated in PTEN cells and this elevated expression is reduced upon reexpression of PTEN. TCF promoter/luciferase reporter assays and gel mobility shift analysis demonstrate that PTEN also suppresses TCF transcriptional activity. Furthermore, the constitutively elevated expression of cyclin D1, a beta-catenin/TCF-regulated gene, is also suppressed upon reexpression of PTEN. Mechanistically, PTEN increases the phosphorylation of beta-catenin and enhances its rate of degradation. We define a pathway that involves mainly integrin-linked kinase and glycogen synthase kinase 3 in the PTEN-dependent regulation of beta-catenin stability, nuclear beta-catenin expression, and transcriptional activity. Our data indicate that beta-catenin/TCF-mediated gene transcription is regulated by PTEN, and this may represent a key mechanism by which PTEN suppresses tumor progression.

Show MeSH
Related in: MedlinePlus