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Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling

BACKGROUND: Clusterin (CLU) is an enigmatic molecule associated with various physiological processes and disease states. Different modes of cellular stress lead to increased CLU levels, and additionally numerous growth factors and cytokines affect the expression of the CLU gene. APC and c-MYC, both...

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Autores principales: Schepeler, Troels, Mansilla, Francisco, Christensen, Lise L, Ørntoft, Torben F, Andersen, Claus L
Formato: Texto
Lenguaje:English
Publicado: BioMed Central 2007
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976611/
https://www.ncbi.nlm.nih.gov/pubmed/17634137
http://dx.doi.org/10.1186/1750-2187-2-6
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author Schepeler, Troels
Mansilla, Francisco
Christensen, Lise L
Ørntoft, Torben F
Andersen, Claus L
author_facet Schepeler, Troels
Mansilla, Francisco
Christensen, Lise L
Ørntoft, Torben F
Andersen, Claus L
author_sort Schepeler, Troels
collection PubMed
description BACKGROUND: Clusterin (CLU) is an enigmatic molecule associated with various physiological processes and disease states. Different modes of cellular stress lead to increased CLU levels, and additionally numerous growth factors and cytokines affect the expression of the CLU gene. APC and c-MYC, both intimately linked to the Wnt signaling pathway have previously been shown to influence CLU levels, and we therefore investigated if changes in Wnt signaling activity in vitro could regulate the expression of one, or more, of several CLU mRNA and protein variants. RESULTS: Over-expression of the cytoplasmic domain of E-cadherin tagged with GFP was used to abrogate Wnt signaling activity in LS174T and HCT116 colon carcinoma cells. This fusion construct sequestered signaling competent β-catenin whereby Wnt signaling was abrogated, and consequently cytoplasmic CLU protein levels increased as demonstrated by immunofluorescence. To determine which branch of the Wnt pathway was mediating the CLU response, we over-expressed dominant negative (dn) TCF1 and TCF4 transcription factors in stably transfected LS174T cells. We observed both intra- and extracellular levels of CLU protein to be induced by dnTCF1 but not dnTCF4. Subsequent analysis of the expression levels of three CLU mRNA variants by real time RT-PCR revealed only one CLU mRNA variant to be responsive to dnTCF1 over-expression. 5'-end RACE indicated that this CLU mRNA variant was shorter at the 5'-end than previously reported, and accordingly the translated protein was predicted to be shorter at the N-terminus and destined to the secretory pathway which fit our observations. Examination of the immediate expression kinetics of CLU after dnTCF1 over-expression using real time RT-PCR indicated that CLU might be a secondary Wnt target. CONCLUSION: In conclusion, we have demonstrated that the Wnt signaling pathway specifically regulates one out of three CLU mRNA variants via TCF1. This CLU transcript is shorter at the 5' end than reported by the RefSeq database, and produces the intracellular 60 kDa CLU protein isoform which is secreted as a ~80 kDa protein after post-translational processing.
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spelling pubmed-19766112007-09-15 Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling Schepeler, Troels Mansilla, Francisco Christensen, Lise L Ørntoft, Torben F Andersen, Claus L J Mol Signal Research Article BACKGROUND: Clusterin (CLU) is an enigmatic molecule associated with various physiological processes and disease states. Different modes of cellular stress lead to increased CLU levels, and additionally numerous growth factors and cytokines affect the expression of the CLU gene. APC and c-MYC, both intimately linked to the Wnt signaling pathway have previously been shown to influence CLU levels, and we therefore investigated if changes in Wnt signaling activity in vitro could regulate the expression of one, or more, of several CLU mRNA and protein variants. RESULTS: Over-expression of the cytoplasmic domain of E-cadherin tagged with GFP was used to abrogate Wnt signaling activity in LS174T and HCT116 colon carcinoma cells. This fusion construct sequestered signaling competent β-catenin whereby Wnt signaling was abrogated, and consequently cytoplasmic CLU protein levels increased as demonstrated by immunofluorescence. To determine which branch of the Wnt pathway was mediating the CLU response, we over-expressed dominant negative (dn) TCF1 and TCF4 transcription factors in stably transfected LS174T cells. We observed both intra- and extracellular levels of CLU protein to be induced by dnTCF1 but not dnTCF4. Subsequent analysis of the expression levels of three CLU mRNA variants by real time RT-PCR revealed only one CLU mRNA variant to be responsive to dnTCF1 over-expression. 5'-end RACE indicated that this CLU mRNA variant was shorter at the 5'-end than previously reported, and accordingly the translated protein was predicted to be shorter at the N-terminus and destined to the secretory pathway which fit our observations. Examination of the immediate expression kinetics of CLU after dnTCF1 over-expression using real time RT-PCR indicated that CLU might be a secondary Wnt target. CONCLUSION: In conclusion, we have demonstrated that the Wnt signaling pathway specifically regulates one out of three CLU mRNA variants via TCF1. This CLU transcript is shorter at the 5' end than reported by the RefSeq database, and produces the intracellular 60 kDa CLU protein isoform which is secreted as a ~80 kDa protein after post-translational processing. BioMed Central 2007-07-16 /pmc/articles/PMC1976611/ /pubmed/17634137 http://dx.doi.org/10.1186/1750-2187-2-6 Text en Copyright © 2007 Schepeler et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Schepeler, Troels
Mansilla, Francisco
Christensen, Lise L
Ørntoft, Torben F
Andersen, Claus L
Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling
title Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling
title_full Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling
title_fullStr Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling
title_full_unstemmed Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling
title_short Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling
title_sort clusterin expression can be modulated by changes in tcf1-mediated wnt signaling
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976611/
https://www.ncbi.nlm.nih.gov/pubmed/17634137
http://dx.doi.org/10.1186/1750-2187-2-6
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