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Manijeh Pasdar - One of the best experts on this subject based on the ideXlab platform.
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Plakoglobin restores tumor suppressor activity of p53R175H mutant by sequestering the oncogenic potential of β‐catenin
Cancer science, 2018Co-Authors: Mahsa Alaee, Kristina Nool, Manijeh PasdarAbstract:Tumor suppressor/transcription factor p53 is mutated in over 50% of all cancers. Some mutant p53 proteins have not only lost tumor suppressor activities but they also gain oncogenic functions (GOF). One of the most frequently expressed GOF p53 mutants is Arg175His (p53R175H ) with well-documented roles in cancer development and progression. Plakoglobin is a cell adhesion and signaling protein and a paralog of β-catenin. Unlike β-catenin that has oncogenic function through its role in the Wnt pathway, Plakoglobin generally acts as a tumor/metastasis suppressor. We have shown that Plakoglobin interacted with wild type and a number of p53 mutants in various carcinoma cell lines. Plakoglobin and mutant p53 interacted with the promoter and regulated the expression of several p53 target genes. Furthermore, Plakoglobin interactions with p53 mutants restored their tumor suppressor/metastasis activities in vitro. GOF p53 mutants induce accumulation and oncogenic activation of β-catenin. Previously, we showed that one mechanism by which Plakoglobin may suppress tumorigenesis is by sequestering β-catenin's oncogenic activity. Here, we examined the effects of p53R175H expression on β-catenin accumulation and transcriptional activation and their modifications by Plakoglobin coexpression. We showed that p53R175H expression in Plakoglobin null cells increased total and nuclear levels of β-catenin and its transcriptional activity. Coexpression of Plakoglobin in these cells promoted β-catenin's proteasomal degradation, and decreased its nuclear levels and transactivation. Wnt/β-catenin targets, c-MYC and S100A4 were upregulated in p53R175H cells and were downregulated when Plakoglobin was coexpressed. Plakoglobin-p53R175H cells also showed significant reduction in their migration and invasion in vitro.
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Beyond cell-cell adhesion: Plakoglobin and the regulation of tumorigenesis and metastasis
Oncotarget, 2017Co-Authors: Zackie Aktary, Mahsa Alaee, Manijeh PasdarAbstract:// Zackie Aktary 1,2,* , Mahsa Alaee 1,* and Manijeh Pasdar 1 1 Department of Oncology, University of Alberta, Edmonton, Alberta, Canada 2 Institut Curie, Orsay, France * These authors have contributed equally to this study Correspondence to: Manijeh Pasdar, email: // Keywords : Plakoglobin, γ-catenin, tumor/metastasis suppressor, p53, gene expression Received : October 28, 2016 Accepted : December 16, 2016 Published : February 23, 2017 Abstract Plakoglobin (also known as γ-catenin) is a member of the Armadillo family of proteins and a paralog of β-catenin. Plakoglobin is a component of both the adherens junctions and desmosomes, and therefore plays a vital role in the regulation of cell-cell adhesion. Similar to β-catenin, Plakoglobin is capable of participating in cell signaling in addition to its role in cell-cell adhesion. In this context, β-catenin has a well-documented oncogenic potential as a component of the Wnt signaling pathway. In contrast, while some studies have suggested a tumor promoting activity of Plakoglobin in a cell/malignancy specific context, it generally acts as a tumor/metastasis suppressor. How Plakoglobin acts as a growth/metastasis inhibitory protein has remained, until recently, unclear. Recent evidence suggests that Plakoglobin may suppress tumorigenesis and metastasis by multiple mechanisms, including the suppression of oncogenic signaling, interactions with various proteins involved in tumorigenesis and metastasis, and the regulation of the expression of genes involved in these processes. This review is primarily focused on various mechanisms by which Plakoglobin may inhibit tumorigenesis and metastasis.
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Plakoglobin Represses SATB1 Expression and Decreases In Vitro Proliferation, Migration and Invasion
2016Co-Authors: Zackie Aktary, Manijeh PasdarAbstract:Plakoglobin (c-catenin) is a homolog of b-catenin with dual adhesive and signaling functions. Plakoglobin participates in cell-cell adhesion as a component of the adherens junction and desmosomes whereas its signaling function is mediated by its interactions with various intracellular protein partners. To determine the role of Plakoglobin during tumorigenesis and metastasis, we expressed Plakoglobin in the human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their Plakoglobin-expressing transfectants (SCC9-PG). We observed that the mRNA levels of SATB1, the oncogenic chromatin remodeling factor, were decreased approximately 3-fold in SCC9-PG cells compared to parental SCC9 cells. Here, we showed that Plakoglobin decreased levels of SATB1 mRNA and protein in SCC9-PG cells and that Plakoglobin and p53 associated with the SATB1 promoter. Plakoglobin expression also resulted in decreased SATB1 promoter activity. These results were confirmed following Plakoglobin expression in the very low Plakoglobin expressing and invasive mammary carcinoma cell line MDA-MB-231 cells (MDA-231-PG). In addition, knockdown of endogenous Plakoglobin in the non-invasive mammary carcinoma MCF-7 cells (MCF-7-shPG) resulted in increased SATB1 mRNA and protein. Plakoglobin expression also resulted in increased mRNA and protein levels of the metastasis suppressor Nm23-H1, a SATB1 target gene. Furthermore, the levels of various SATB1 target genes involved in tumorigenesis and metastasis were altered in MCF-7-shPG cells relative to parental MCF-7 cells. Finally, Plakoglobin expression resulted in decreased in vitr
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Plakoglobin Reduces the in vitro Growth, Migration and Invasion of Ovarian Cancer Cells Expressing N-Cadherin and Mutant p53 - Fig 3
2016Co-Authors: Mahsa Alaee, Ghazal Danesh, Manijeh PasdarAbstract:(A) Migration (Left) and invasion (Right) of IOSE-364, OV-90, ES-2 cells. Cultures were processed for in vitro migration and invasion assays as described in Materials and Methods. The number of migrated/invaded cells was normalized to those of the IOSE-364 cells. (B) Expression of E-cadherin, N-cadherin and Plakoglobin in ES-2 transfectants expressing E-cadherin (ES-2-E-cad) or Plakoglobin (ES-2-PG) or N-cadherin shRNAs (ES-2-shN-cad). Stable transfectants were processed for immunoblotting using E-cadherin, Plakoglobin and N-cadherin antibodies. To confirm equal loadings, the same cell lysates were processed with actin antibodies. (C) Subcellular distribution and colocalization of E-cadherin, N-cadherin and Plakoglobin in ES-2- E-cad, ES-2-PG and ES-2-shN-cad transfectants. Stable transfectants were established on coverslips and processed for double immunofluorescence with E-cadherin (E-cad, red) or N-cadherin (N-cad, red) and Plakoglobin (PG, green) antibodies. Nuclei were stained with DAPI (blue). Bar, 25 μm.
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Plakoglobin represses SATB1 expression and decreases in vitro proliferation, migration and invasion.
PloS one, 2013Co-Authors: Zackie Aktary, Manijeh PasdarAbstract:Plakoglobin (c-catenin) is a homolog of b-catenin with dual adhesive and signaling functions. Plakoglobin participates in cell-cell adhesion as a component of the adherens junction and desmosomes whereas its signaling function is mediated by its interactions with various intracellular protein partners. To determine the role of Plakoglobin during tumorigenesis and metastasis, we expressed Plakoglobin in the human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their Plakoglobin-expressing transfectants (SCC9-PG). We observed that the mRNA levels of SATB1, the oncogenic chromatin remodeling factor, were decreased approximately 3-fold in SCC9-PG cells compared to parental SCC9 cells. Here, we showed that Plakoglobin decreased levels of SATB1 mRNA and protein in SCC9-PG cells and that Plakoglobin and p53 associated with the SATB1 promoter. Plakoglobin expression also resulted in decreased SATB1 promoter activity. These results were confirmed following Plakoglobin expression in the very low Plakoglobin expressing and invasive mammary carcinoma cell line MDA-MB-231 cells (MDA-231-PG). In addition, knockdown of endogenous Plakoglobin in the non-invasive mammary carcinoma MCF-7 cells (MCF-7-shPG) resulted in increased SATB1 mRNA and protein. Plakoglobin expression also resulted in increased mRNA and protein levels of the metastasis suppressor Nm23-H1, a SATB1 target gene. Furthermore, the levels of various SATB1 target genes involved in tumorigenesis and metastasis were altered in MCF-7-shPG cells relative to parental MCF-7 cells. Finally, Plakoglobin expression resulted in decreased in vitro proliferation, migration and invasion in different carcinoma cell lines. Together with the results of our previous studies, the data suggests that Plakoglobin suppresses tumorigenesis and metastasis through the regulation of genes involved in these processes.
Avri Ben-ze'ev - One of the best experts on this subject based on the ideXlab platform.
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Reduced expression of Plakoglobin correlates with adverse outcome in patients with neuroblastoma.
The American journal of pathology, 2001Co-Authors: Raya Amitay, Avri Ben-ze'ev, Dvora Nass, Dafna Meitar, Iris Goldberg, Ben Davidson, Luba Trakhtenbrot, F. Brok-simoni, Gideon Rechavi, Yael KaufmannAbstract:Plakoglobin and its homologue β-catenin are cytoplasmic proteins that mediate adhesive functions by interacting with cadherin receptors and signaling activities by interacting with transcription factors. It has been suggested that Plakoglobin can suppress tumorigenicity whereas β-catenin can act as an oncogene. We investigated the correlation between the expression pattern of N-cadherin, β-catenin, and Plakoglobin and tumor behavior in primary tumors of 20 neuroblastoma patients of all stages and in 11 human neuroblastoma cell lines. N-cadherin and β-catenin were detected in 9 of 11 and 11 of 11 cell lines, respectively, whereas Plakoglobin was undetectable or severely reduced in 6 of 11 cell lines. Tumor cells from 16 of 20 patients expressed N-cadherin and 20 of 20 patients expressed β-catenin at levels similar to those of normal ganglion cells. Plakoglobin was undetectable in 9 of 20 tumors. Plakoglobin deficiency in the primary tumors was significantly associated with adverse clinical outcome. Five of the patients with Plakoglobin-negative tumors died whereas four patients are alive without evident disease. In contrast, all patients with Plakoglobin-positive tumors are alive; 2 of 11 are alive with the disease and 9 of 11 are alive without evident disease. These results suggest that down-regulation of Plakoglobin may be of prognostic value for neuroblastoma patients aspredictor of poor outcome.
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Differential Mechanisms of LEF/TCF Family-Dependent Transcriptional Activation by β-Catenin and Plakoglobin
Molecular and cellular biology, 2000Co-Authors: Jacob Zhurinsky, Michael Shtutman, Avri Ben-ze'evAbstract:β-Catenin and Plakoglobin are highly homologous components of cell-cell adherens junctions linking cadherin receptors to the actin cytoskeleton. β-Catenin, in addition, activates transcription by forming a complex with LEF/TCF family transcription factors in the nucleus. Plakoglobin can also bind to LEF-1 and, when overexpressed in mammalian cells, enhances LEF-1-directed transcription. Plakoglobin overexpression, however, results in the elevation and nuclear translocation of endogenous β-catenin. We show here, by DNA mobility shift analysis, that the formation of a Plakoglobin-LEF/TCF-DNA complex in vitro is very inefficient compared to a complex containing β-catenin-LEF-DNA. Moreover, in Plakoglobin-transfected cells Plakoglobin-LEF/TCF-DNA complexes were not formed; rather, the endogenous β-catenin, whose level is elevated by Plakoglobin transfection, formed a β-catenin–LEF–DNA complex. Removal of the N- and C-terminal domains of both β-catenin and Plakoglobin (leaving the armadillo repeat domain intact) induced Plakoglobin-LEF-DNA complex formation and also enhanced β-catenin–LEF–DNA complexing, both with in vitro-translated components and in transfected cells. Transfection with these truncated catenins increased endogenous β-catenin levels, but the truncated catenins acted as dominant-negative inhibitors of β-catenin-driven transcription by forming transcriptionally inactive complexes with LEF-1. When these catenin mutants were prevented from entering the nucleus, by their fusion to the connexin transmembrane domain, they indirectly activated transcription by increasing endogenous β-catenin levels. These results suggest that overexpression of Plakoglobin does not directly activate transcription and that formation of catenin-LEF-DNA complexes is negatively regulated by the catenin N- and C-terminal domains.
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Differential interaction of Plakoglobin and β-catenin with the ubiquitin-proteasome system
Oncogene, 2000Co-Authors: Einat Sadot, Benjamin Geiger, Inbal Simcha, Kazuhiro Iwai, Aaron Ciechanover, Avri Ben-ze'evAbstract:β-Catenin and Plakoglobin are closely related armadillo family proteins with shared and distinct properties; Both are associated with cadherins in actin-containing adherens junctions. Plakoglobin is also found in desmosomes where it anchors intermediate filaments to the desmosomal plaques. β-Catenin, on the other hand, is a component of the Wnt signaling pathway, which is involved in embryonic morphogenesis and tumorigenesis. A key step in the regulation of this pathway involves modulation of β-catenin stability. A multiprotein complex, regulated by Wnt, directs the phosphorylation of β-catenin and its degradation by the ubiquitin-proteasome system. Plakoglobin can also associate with members of this complex, but inhibition of proteasomal degradation has little effect on its levels while dramatically increasing the levels of β-catenin. β-TrCP, an F-box protein of the SCF E3 ubiquitin ligase complex, was recently shown to play a role in the turnover of β-catenin. To elucidate the basis for the apparent differences in the turnover of β-catenin and Plakoglobin we compared the handling of these two proteins by the ubiquitin-proteasome system. We show here that a deletion mutant of β-TrCP, lacking the F-box, can stabilize the endogenous β-catenin leading to its nuclear translocation and induction of β-catenin/LEF-1-directed transcription, without affecting the levels of Plakoglobin. However, when Plakoglobin was overexpressed, it readily associated with β-TrCP, efficiently competed with β-catenin for binding to β-TrCP and became polyubiquitinated. Fractionation studies revealed that about 85% of Plakoglobin in 293 cells, is Triton X-100-insoluble compared to 50% of β-catenin. These results suggest that while both Plakoglobin and β-catenin can comparably interact with β-TrCP and the ubiquitination system, the sequestration of Plakoglobin by the membrane-cytoskeleton system renders it inaccessible to the proteolytic machinery and stabilizes it.
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Differential Nuclear Translocation and Transactivation Potential of β-Catenin and Plakoglobin
The Journal of cell biology, 1998Co-Authors: Inbal Simcha, Jacob Zhurinsky, Michael Shtutman, Benjamin Geiger, Daniela Salomon, Einat Sadot, Avri Ben-ze'evAbstract:β-Catenin and Plakoglobin are homologous proteins that function in cell adhesion by linking cadherins to the cytoskeleton and in signaling by transactivation together with lymphoid-enhancing binding/T cell (LEF/TCF) transcription factors. Here we compared the nuclear translocation and transactivation abilities of β-catenin and Plakoglobin in mammalian cells. Overexpression of each of the two proteins in MDCK cells resulted in nuclear translocation and formation of nuclear aggregates. The β-catenin-containing nuclear structures also contained LEF-1 and vinculin, while Plakoglobin was inefficient in recruiting these molecules, suggesting that its interaction with LEF-1 and vinculin is significantly weaker. Moreover, transfection of LEF-1 translocated endogenous β-catenin, but not Plakoglobin to the nucleus. Chimeras consisting of Gal4 DNA-binding domain and the transactivation domains of either Plakoglobin or β-catenin were equally potent in transactivating a Gal4-responsive reporter, whereas activation of LEF-1– responsive transcription was significantly higher with β-catenin. Overexpression of wild-type Plakoglobin or mutant β-catenin lacking the transactivation domain induced accumulation of the endogenous β-catenin in the nucleus and LEF-1–responsive transactivation. It is further shown that the constitutive β-catenin–dependent transactivation in SW480 colon carcinoma cells and its nuclear localization can be inhibited by overexpressing N-cadherin or α-catenin. The results indicate that (a) Plakoglobin and β-catenin differ in their nuclear translocation and complexing with LEF-1 and vinculin; (b) LEF-1–dependent transactivation is preferentially driven by β-catenin; and (c) the cytoplasmic partners of β-catenin, cadherin and α-catenin, can sequester it to the cytoplasm and inhibit its transcriptional activity.
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Regulation of β-Catenin Levels and Localization by Overexpression of Plakoglobin and Inhibition of the Ubiquitin-Proteasome System
The Journal of cell biology, 1997Co-Authors: Daniela Salomon, Margaret J. Wheelock, Keith R. Johnson, Paula A. Sacco, Sujata Guha Roy, Inbal Simcha, Avri Ben-ze'evAbstract:β-Catenin and Plakoglobin (γ-catenin) are closely related molecules of the armadillo family of proteins. They are localized at the submembrane plaques of cell–cell adherens junctions where they form independent complexes with classical cadherins and α-catenin to establish the link with the actin cytoskeleton. Plakoglobin is also found in a complex with desmosomal cadherins and is involved in anchoring intermediate filaments to desmosomal plaques. In addition to their role in junctional assembly, β-catenin has been shown to play an essential role in signal transduction by the Wnt pathway that results in its translocation into the nucleus. To study the relationship between Plakoglobin expression and the level of β-catenin, and the localization of these proteins in the same cell, we employed two different tumor cell lines that express N-cadherin, and α- and β-catenin, but no Plakoglobin or desmosomal components. Individual clones expressing various levels of Plakoglobin were established by stable transfection. Plakoglobin overexpression resulted in a dose-dependent decrease in the level of β-catenin in each clone. Induction of Plakoglobin expression increased the turnover of β-catenin without affecting RNA levels, suggesting posttranslational regulation of β-catenin. In Plakoglobin overexpressing cells, both β-catenin and Plakoglobin were localized at cell– cell junctions. Stable transfection of mutant Plakoglobin molecules showed that deletion of the N-cadherin binding domain, but not the α-catenin binding domain, abolished β-catenin downregulation. Inhibition of the ubiquitin-proteasome pathway in Plakoglobin overexpressing cells blocked the decrease in β-catenin levels and resulted in accumulation of both β-catenin and Plakoglobin in the nucleus. These results suggest that ( a ) Plakoglobin substitutes effectively with β-catenin for association with N-cadherin in adherens junctions, ( b ) extrajunctional β-catenin is rapidly degraded by the proteasome-ubiquitin system but, ( c ) excess β-catenin and Plakoglobin translocate into the nucleus.
Zackie Aktary - One of the best experts on this subject based on the ideXlab platform.
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Beyond cell-cell adhesion: Plakoglobin and the regulation of tumorigenesis and metastasis
Oncotarget, 2017Co-Authors: Zackie Aktary, Mahsa Alaee, Manijeh PasdarAbstract:// Zackie Aktary 1,2,* , Mahsa Alaee 1,* and Manijeh Pasdar 1 1 Department of Oncology, University of Alberta, Edmonton, Alberta, Canada 2 Institut Curie, Orsay, France * These authors have contributed equally to this study Correspondence to: Manijeh Pasdar, email: // Keywords : Plakoglobin, γ-catenin, tumor/metastasis suppressor, p53, gene expression Received : October 28, 2016 Accepted : December 16, 2016 Published : February 23, 2017 Abstract Plakoglobin (also known as γ-catenin) is a member of the Armadillo family of proteins and a paralog of β-catenin. Plakoglobin is a component of both the adherens junctions and desmosomes, and therefore plays a vital role in the regulation of cell-cell adhesion. Similar to β-catenin, Plakoglobin is capable of participating in cell signaling in addition to its role in cell-cell adhesion. In this context, β-catenin has a well-documented oncogenic potential as a component of the Wnt signaling pathway. In contrast, while some studies have suggested a tumor promoting activity of Plakoglobin in a cell/malignancy specific context, it generally acts as a tumor/metastasis suppressor. How Plakoglobin acts as a growth/metastasis inhibitory protein has remained, until recently, unclear. Recent evidence suggests that Plakoglobin may suppress tumorigenesis and metastasis by multiple mechanisms, including the suppression of oncogenic signaling, interactions with various proteins involved in tumorigenesis and metastasis, and the regulation of the expression of genes involved in these processes. This review is primarily focused on various mechanisms by which Plakoglobin may inhibit tumorigenesis and metastasis.
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Plakoglobin Represses SATB1 Expression and Decreases In Vitro Proliferation, Migration and Invasion
2016Co-Authors: Zackie Aktary, Manijeh PasdarAbstract:Plakoglobin (c-catenin) is a homolog of b-catenin with dual adhesive and signaling functions. Plakoglobin participates in cell-cell adhesion as a component of the adherens junction and desmosomes whereas its signaling function is mediated by its interactions with various intracellular protein partners. To determine the role of Plakoglobin during tumorigenesis and metastasis, we expressed Plakoglobin in the human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their Plakoglobin-expressing transfectants (SCC9-PG). We observed that the mRNA levels of SATB1, the oncogenic chromatin remodeling factor, were decreased approximately 3-fold in SCC9-PG cells compared to parental SCC9 cells. Here, we showed that Plakoglobin decreased levels of SATB1 mRNA and protein in SCC9-PG cells and that Plakoglobin and p53 associated with the SATB1 promoter. Plakoglobin expression also resulted in decreased SATB1 promoter activity. These results were confirmed following Plakoglobin expression in the very low Plakoglobin expressing and invasive mammary carcinoma cell line MDA-MB-231 cells (MDA-231-PG). In addition, knockdown of endogenous Plakoglobin in the non-invasive mammary carcinoma MCF-7 cells (MCF-7-shPG) resulted in increased SATB1 mRNA and protein. Plakoglobin expression also resulted in increased mRNA and protein levels of the metastasis suppressor Nm23-H1, a SATB1 target gene. Furthermore, the levels of various SATB1 target genes involved in tumorigenesis and metastasis were altered in MCF-7-shPG cells relative to parental MCF-7 cells. Finally, Plakoglobin expression resulted in decreased in vitr
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Plakoglobin represses SATB1 expression and decreases in vitro proliferation, migration and invasion.
PloS one, 2013Co-Authors: Zackie Aktary, Manijeh PasdarAbstract:Plakoglobin (c-catenin) is a homolog of b-catenin with dual adhesive and signaling functions. Plakoglobin participates in cell-cell adhesion as a component of the adherens junction and desmosomes whereas its signaling function is mediated by its interactions with various intracellular protein partners. To determine the role of Plakoglobin during tumorigenesis and metastasis, we expressed Plakoglobin in the human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their Plakoglobin-expressing transfectants (SCC9-PG). We observed that the mRNA levels of SATB1, the oncogenic chromatin remodeling factor, were decreased approximately 3-fold in SCC9-PG cells compared to parental SCC9 cells. Here, we showed that Plakoglobin decreased levels of SATB1 mRNA and protein in SCC9-PG cells and that Plakoglobin and p53 associated with the SATB1 promoter. Plakoglobin expression also resulted in decreased SATB1 promoter activity. These results were confirmed following Plakoglobin expression in the very low Plakoglobin expressing and invasive mammary carcinoma cell line MDA-MB-231 cells (MDA-231-PG). In addition, knockdown of endogenous Plakoglobin in the non-invasive mammary carcinoma MCF-7 cells (MCF-7-shPG) resulted in increased SATB1 mRNA and protein. Plakoglobin expression also resulted in increased mRNA and protein levels of the metastasis suppressor Nm23-H1, a SATB1 target gene. Furthermore, the levels of various SATB1 target genes involved in tumorigenesis and metastasis were altered in MCF-7-shPG cells relative to parental MCF-7 cells. Finally, Plakoglobin expression resulted in decreased in vitro proliferation, migration and invasion in different carcinoma cell lines. Together with the results of our previous studies, the data suggests that Plakoglobin suppresses tumorigenesis and metastasis through the regulation of genes involved in these processes.
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Plakoglobin interacts with the transcription factor p53 and regulates the expression of 14-3-3σ.
Journal of Cell Science, 2013Co-Authors: Zackie Aktary, Stephen C. Kulak, John R. Mackey, Nadia Jahroudi, Manijeh PasdarAbstract:Plakoglobin (γ-catenin), a constituent of the adherens junction and desmosomes, has signaling capabilities typically associated with tumor/metastasis suppression through mechanisms that remain undefined. To determine the role of Plakoglobin during tumorigenesis and metastasis, we expressed Plakoglobin in human tongue squamous cell carcinoma (SCC9) cells and compared the mRNA profiles of parental SCC9 cells and their Plakoglobin-expressing transfectants (SCC9-PG). We detected several p53-target genes whose levels were altered upon Plakoglobin expression. In this study, we identified the p53 regulated tumor suppressor 14-3-3σ as a direct Plakoglobin-p53 target gene. Coimmunoprecipitation experiments revealed that Plakoglobin and p53 interact, and chromatin immunoprecipitation and electrophoretic mobility shift assays revealed that Plakoglobin and p53 associate with the 14-3-3σ promoter. Furthermore, luciferase reporter assays showed that p53 transcriptional activity is increased in the presence of Plakoglobin. Finally, knockdown of Plakoglobin in MCF-7 cells followed by luciferase assays confirmed that p53 transcriptional activity is enhanced in the presence of Plakoglobin. Our data suggest that Plakoglobin regulates gene expression in conjunction with p53 and that Plakoglobin may regulate p53 transcriptional activity, which may account, in part, for the tumor/metastasis suppressor activity of Plakoglobin.
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Abstract 1185: Plakoglobin (β-catenin) interacts with the transcription factor p53 and regulates the expression of genes involved in tumorigenesis and metastasis
Molecular and Cellular Biology, 2012Co-Authors: Zackie Aktary, Manijeh PasdarAbstract:Plakoglobin (β-catenin) and β-catenin are highly homologous proteins that function in cell-cell adhesion and signaling. Both proteins exist in a cadherin-associated form, which mediates adhesion, and in a distinct cytosolic/nuclear form, which plays a signaling role. Despite their interactions with common cellular partners, β-catenin has well documented oncogenic potential while Plakoglobin expression is generally associated with tumor/metastasis suppression. The underlying mechanisms for this activity of Plakoglobin are unclear. We previously showed that Plakoglobin expression in oral squamous carcinoma cells (SCC9-PG) resulted in a mesenchymal-epidermoid transition, which was concurrent with increased N-cadherin and decreased β-catenin levels. Comparison of the RNA and protein profiles of SCC9 cells and SCC9-PG transfectants identified a number of differentially expressed proteins and transcripts, which suggested that Plakoglobin regulates gene expression. Closer analysis of the mRNA profiles of SCC9 and SCC9-PG cells identified several p53 target genes that were differentially expressed upon Plakoglobin expression, suggesting that Plakoglobin may regulate gene expression in conjunction with p53. Here, we describe the ability of Plakoglobin to regulate three potential p53 target genes: the tumor and metastasis suppressors 14-3-3α and Nm23 and the tumor promoter SATB1. We show, by RT-PCR and Western blot, that Plakoglobin expression results in increased 14-3-3σ and Nm23 and decreased SATB1 mRNA and protein levels. Co-immunoprecipitation experiments show that Plakoglobin and p53 interact, and that these interactions occur in both the cytoplasm and the nucleus. Chromatin immunoprecipitation and Electrophoretic mobility shift assays (EMSA) indicate that Plakoglobin and p53 associate with the promoters of these target genes. Finally, luciferase reporter assays confirm that Plakoglobin regulates the expression of these p53 target genes. Taken together, the results of these studies provide strong evidence that Plakoglobin plays an active role in regulating gene expression, a function that has not often been associated with Plakoglobin. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1185. doi:1538-7445.AM2012-1185
Yoshitaka Sekido - One of the best experts on this subject based on the ideXlab platform.
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Plakoglobin γ catenin has tcf lef family dependent transcriptional activity in β catenin deficient cell line
Oncogene, 2004Co-Authors: Osamu Maeda, Noriyasu Usami, Masashi Kondo, Masahide Takahashi, Hidemi Goto, Kaoru Shimokata, Kazuo Kusugami, Yoshitaka SekidoAbstract:β-Catenin is an essential element for the transcriptional activation of target genes in the Wnt signaling cascade and is also a cell adhesion molecule that couples with cadherins. Although Plakoglobin (γ-catenin), a closely related homologue of β-catenin, is also known to be a cell adhesion molecule, its function as a transcriptional factor has not been revealed in detail. Using a human malignant mesothelioma cell line, NCI-H28, in which we have identified a homozygous deletion of the β-catenin gene, we studied whether Plakoglobin has a T-cell factor/lymphocyte enhancer factor (TCF/LEF) family-dependent transcriptional activity. Transfection with the wild-type Plakoglobin expression vector induced accumulation of Plakoglobin in the nucleus. Immunoprecipitation assay with cotransfection of Plakoglobin and either TCF-4 or LEF-1 detected binding of Plakoglobin to TCF-4 or LEF-1. Luciferase reporter assay demonstrated transcriptional activity of the wild-type Plakoglobin when transfected with TCF/LEF, although Plakoglobin showed less activity than β-catenin. Exogenous Plakoglobin was also shown to promote entrance of exogenous β-catenin into the nuclei. Furthermore, small interfering RNA directed against Plakoglobin suppressed expression of endogenous Plakoglobin and its transcriptional activity, suggesting that endogenous Plakoglobin has a weak transcriptional activity. These results suggest that Plakoglobin can activate the Wnt signaling cascade directly without interaction of β-catenin, and that Plakoglobin has multiple functions as a transcriptional activator and a cell adhesion molecule like β-catenin.
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Plakoglobin (γ-catenin) has TCF/LEF family-dependent transcriptional activity in β-catenin-deficient cell line
Oncogene, 2003Co-Authors: Osamu Maeda, Noriyasu Usami, Masashi Kondo, Masahide Takahashi, Hidemi Goto, Kaoru Shimokata, Kazuo Kusugami, Yoshitaka SekidoAbstract:β-Catenin is an essential element for the transcriptional activation of target genes in the Wnt signaling cascade and is also a cell adhesion molecule that couples with cadherins. Although Plakoglobin (γ-catenin), a closely related homologue of β-catenin, is also known to be a cell adhesion molecule, its function as a transcriptional factor has not been revealed in detail. Using a human malignant mesothelioma cell line, NCI-H28, in which we have identified a homozygous deletion of the β-catenin gene, we studied whether Plakoglobin has a T-cell factor/lymphocyte enhancer factor (TCF/LEF) family-dependent transcriptional activity. Transfection with the wild-type Plakoglobin expression vector induced accumulation of Plakoglobin in the nucleus. Immunoprecipitation assay with cotransfection of Plakoglobin and either TCF-4 or LEF-1 detected binding of Plakoglobin to TCF-4 or LEF-1. Luciferase reporter assay demonstrated transcriptional activity of the wild-type Plakoglobin when transfected with TCF/LEF, although Plakoglobin showed less activity than β-catenin. Exogenous Plakoglobin was also shown to promote entrance of exogenous β-catenin into the nuclei. Furthermore, small interfering RNA directed against Plakoglobin suppressed expression of endogenous Plakoglobin and its transcriptional activity, suggesting that endogenous Plakoglobin has a weak transcriptional activity. These results suggest that Plakoglobin can activate the Wnt signaling cascade directly without interaction of β-catenin, and that Plakoglobin has multiple functions as a transcriptional activator and a cell adhesion molecule like β-catenin.
Jacob Zhurinsky - One of the best experts on this subject based on the ideXlab platform.
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PML Is a Target Gene of β-Catenin and Plakoglobin, and Coactivates β-Catenin-mediated Transcription
Cancer Research, 2002Co-Authors: Michael Shtutman, Jacob Zhurinsky, Moshe Oren, Elina LevinaAbstract:β-Catenin and its close homologue Plakoglobin (γ-catenin) are major constituents of submembranal cell-cell adhesion sites. In addition, β-catenin is a key component in the canonical Wnt pathway. Aberrantly activated β-catenin signaling contributes to cancer progression by inducing [in complex with lymphocyte enhancer factor (LEF)/T-cell factor (TCF)] the transcription of proliferation-related genes such as cyclin D1 and c-myc. Plakoglobin can also activate LEF/TCF-mediated transcription. Excessive β-catenin signaling in MEF triggers a p53-mediated antiproliferative response by inducing the expression of ARF. We have demonstrated previously that Plakoglobin also exerts a tumor-suppressive effect in certain cancer cell lines. To identify genes induced by β-catenin and Plakoglobin, DNA microarray analysis was carried out, and PML was among those genes of which the expression was significantly elevated by both Plakoglobin and β-catenin. Activation of the PML promoter by β-catenin and Plakoglobin was LEF/TCF-independent. We found that PML forms a complex with β-catenin in cells, and the two proteins colocalize in the nucleus. In addition, PML, p300, and β-catenin cooperated in transactivation of a subset of β-catenin-responsive genes including ARF and Siamois but not cyclin D1. Retroviral expression of β-catenin, Plakoglobin, or PML suppressed the tumorigenicity of p53-negative human renal carcinoma cells, thus pointing to a novel antioncogenic response triggered by catenins that is mediated by the induction of PML.
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Differential Mechanisms of LEF/TCF Family-Dependent Transcriptional Activation by β-Catenin and Plakoglobin
Molecular and cellular biology, 2000Co-Authors: Jacob Zhurinsky, Michael Shtutman, Avri Ben-ze'evAbstract:β-Catenin and Plakoglobin are highly homologous components of cell-cell adherens junctions linking cadherin receptors to the actin cytoskeleton. β-Catenin, in addition, activates transcription by forming a complex with LEF/TCF family transcription factors in the nucleus. Plakoglobin can also bind to LEF-1 and, when overexpressed in mammalian cells, enhances LEF-1-directed transcription. Plakoglobin overexpression, however, results in the elevation and nuclear translocation of endogenous β-catenin. We show here, by DNA mobility shift analysis, that the formation of a Plakoglobin-LEF/TCF-DNA complex in vitro is very inefficient compared to a complex containing β-catenin-LEF-DNA. Moreover, in Plakoglobin-transfected cells Plakoglobin-LEF/TCF-DNA complexes were not formed; rather, the endogenous β-catenin, whose level is elevated by Plakoglobin transfection, formed a β-catenin–LEF–DNA complex. Removal of the N- and C-terminal domains of both β-catenin and Plakoglobin (leaving the armadillo repeat domain intact) induced Plakoglobin-LEF-DNA complex formation and also enhanced β-catenin–LEF–DNA complexing, both with in vitro-translated components and in transfected cells. Transfection with these truncated catenins increased endogenous β-catenin levels, but the truncated catenins acted as dominant-negative inhibitors of β-catenin-driven transcription by forming transcriptionally inactive complexes with LEF-1. When these catenin mutants were prevented from entering the nucleus, by their fusion to the connexin transmembrane domain, they indirectly activated transcription by increasing endogenous β-catenin levels. These results suggest that overexpression of Plakoglobin does not directly activate transcription and that formation of catenin-LEF-DNA complexes is negatively regulated by the catenin N- and C-terminal domains.
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differential mechanisms of lef tcf family dependent transcriptional activation by β catenin and Plakoglobin
Molecular and Cellular Biology, 2000Co-Authors: Jacob Zhurinsky, Michael Shtutman, Avri BenzeevAbstract:β-Catenin and Plakoglobin are highly homologous components of cell-cell adherens junctions linking cadherin receptors to the actin cytoskeleton. β-Catenin, in addition, activates transcription by forming a complex with LEF/TCF family transcription factors in the nucleus. Plakoglobin can also bind to LEF-1 and, when overexpressed in mammalian cells, enhances LEF-1-directed transcription. Plakoglobin overexpression, however, results in the elevation and nuclear translocation of endogenous β-catenin. We show here, by DNA mobility shift analysis, that the formation of a Plakoglobin-LEF/TCF-DNA complex in vitro is very inefficient compared to a complex containing β-catenin-LEF-DNA. Moreover, in Plakoglobin-transfected cells Plakoglobin-LEF/TCF-DNA complexes were not formed; rather, the endogenous β-catenin, whose level is elevated by Plakoglobin transfection, formed a β-catenin–LEF–DNA complex. Removal of the N- and C-terminal domains of both β-catenin and Plakoglobin (leaving the armadillo repeat domain intact) induced Plakoglobin-LEF-DNA complex formation and also enhanced β-catenin–LEF–DNA complexing, both with in vitro-translated components and in transfected cells. Transfection with these truncated catenins increased endogenous β-catenin levels, but the truncated catenins acted as dominant-negative inhibitors of β-catenin-driven transcription by forming transcriptionally inactive complexes with LEF-1. When these catenin mutants were prevented from entering the nucleus, by their fusion to the connexin transmembrane domain, they indirectly activated transcription by increasing endogenous β-catenin levels. These results suggest that overexpression of Plakoglobin does not directly activate transcription and that formation of catenin-LEF-DNA complexes is negatively regulated by the catenin N- and C-terminal domains.
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Differential Nuclear Translocation and Transactivation Potential of β-Catenin and Plakoglobin
The Journal of cell biology, 1998Co-Authors: Inbal Simcha, Jacob Zhurinsky, Michael Shtutman, Benjamin Geiger, Daniela Salomon, Einat Sadot, Avri Ben-ze'evAbstract:β-Catenin and Plakoglobin are homologous proteins that function in cell adhesion by linking cadherins to the cytoskeleton and in signaling by transactivation together with lymphoid-enhancing binding/T cell (LEF/TCF) transcription factors. Here we compared the nuclear translocation and transactivation abilities of β-catenin and Plakoglobin in mammalian cells. Overexpression of each of the two proteins in MDCK cells resulted in nuclear translocation and formation of nuclear aggregates. The β-catenin-containing nuclear structures also contained LEF-1 and vinculin, while Plakoglobin was inefficient in recruiting these molecules, suggesting that its interaction with LEF-1 and vinculin is significantly weaker. Moreover, transfection of LEF-1 translocated endogenous β-catenin, but not Plakoglobin to the nucleus. Chimeras consisting of Gal4 DNA-binding domain and the transactivation domains of either Plakoglobin or β-catenin were equally potent in transactivating a Gal4-responsive reporter, whereas activation of LEF-1– responsive transcription was significantly higher with β-catenin. Overexpression of wild-type Plakoglobin or mutant β-catenin lacking the transactivation domain induced accumulation of the endogenous β-catenin in the nucleus and LEF-1–responsive transactivation. It is further shown that the constitutive β-catenin–dependent transactivation in SW480 colon carcinoma cells and its nuclear localization can be inhibited by overexpressing N-cadherin or α-catenin. The results indicate that (a) Plakoglobin and β-catenin differ in their nuclear translocation and complexing with LEF-1 and vinculin; (b) LEF-1–dependent transactivation is preferentially driven by β-catenin; and (c) the cytoplasmic partners of β-catenin, cadherin and α-catenin, can sequester it to the cytoplasm and inhibit its transcriptional activity.
