Interplay between microRNAs and WNT/β-catenin signalling pathway regulates epithelial–mesenchymal transition in cancer

2015 ◽  
Vol 51 (12) ◽  
pp. 1638-1649 ◽  
Author(s):  
Nastaran Mohammadi Ghahhari ◽  
Sadegh Babashah
Keyword(s):  
Epithelial Mesenchymal Transition ◽  
Signalling Pathway ◽  
Mesenchymal Transition

scholarly journals Smad7 Binds Differently to Individual and Tandem WW3 and WW4 Domains of WWP2 Ubiquitin Ligase Isoforms

2019 ◽  
Vol 20 (19) ◽  
pp. 4682 ◽  
Author(s):  
Lloyd C. Wahl ◽  
Jessica E. Watt ◽  
Hiu T. T. Yim ◽  
Danielle De Bourcier ◽  
James Tolchard ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Solution Structure ◽  
Epithelial Mesenchymal Transition ◽  
Signalling Pathway ◽  
Substrate Selection ◽  
Ww Domains ◽  
Mesenchymal Transition ◽  
Substrate Peptide ◽  
Tgfβ Signalling

WWP2 is an E3 ubiquitin ligase that differentially regulates the contextual tumour suppressor/progressor TGFβ signalling pathway by alternate isoform expression. WWP2 isoforms select signal transducer Smad2/3 or inhibitor Smad7 substrates for degradation through different compositions of protein–protein interaction WW domains. The WW4 domain-containing WWP2-C induces Smad7 turnover in vivo and positively regulates the metastatic epithelial–mesenchymal transition programme. This activity and the overexpression of these isoforms in human cancers make them candidates for therapeutic intervention. Here, we use NMR spectroscopy to solve the solution structure of the WWP2 WW4 domain and observe the binding characteristics of Smad7 substrate peptide. We also reveal that WW4 has an enhanced affinity for a Smad7 peptide phosphorylated at serine 206 adjacent to the PPxY motif. Using the same approach, we show that the WW3 domain also binds Smad7 and has significantly enhanced Smad7 binding affinity when expressed in tandem with the WW4 domain. Furthermore, and relevant to these biophysical findings, we present evidence for a novel WWP2 isoform (WWP2C-ΔHECT) comprising WW3–WW4 tandem domains and a truncated HECT domain that can inhibit TGFβ signalling pathway activity, providing a further layer of complexity and feedback to the WWP2 regulatory apparatus. Collectively, our data reveal a structural platform for Smad substrate selection by WWP2 isoform WW domains that may be significant in the context of WWP2 isoform switching linked to tumorigenesis.

scholarly journals DNAJB6 governs a novel regulatory loop determining Wnt/β-catenin signalling activity

2012 ◽  
Vol 444 (3) ◽  
pp. 573-580 ◽  
Author(s):  
Mitchell E. Menezes ◽  
Aparna Mitra ◽  
Lalita A. Shevde ◽  
Rajeev S. Samant
Keyword(s):  
Epithelial Mesenchymal Transition ◽  
Tumour Microenvironment ◽  
Negative Control ◽  
Signalling Pathway ◽  
Transition Analysis ◽  
Mesenchymal Transition ◽  
Tumour Metastasis ◽  
Dkk1 Expression ◽  
Exogenous Expression ◽  
Regulatory Loop

DKK1 (dickkopf 1 homologue) is a secreted inhibitor of the Wnt signalling pathway and a critical modulator of tumour promotion and the tumour microenvironment. However, mechanisms regulating DKK1 expression are understudied. DNAJB6 {DnaJ [HSP40 (heat-shock protein 40 kDa)] homologue, subfamily B, member 6} is an HSP40 family member whose expression is compromized during progression of breast cancer and melanoma. Inhibition of the Wnt/β-catenin signalling pathway by up-regulation of DKK1 is one of the key mechanisms by which DNAJB6 suppresses tumour metastasis and EMT (epithelial–mesenchymal transition). Analysis of the DKK1 promoter to define the cis-site responsible for its up-regulation by DNAJB6 revealed the presence of two binding sites for a transcriptional repressor, MSX1 (muscle segment homeobox 1). Our investigations showed that MSX1 binds the DKK1 promoter and inhibits DKK1 transcription. Interestingly, silencing DNAJB6 resulted in up-regulation of MSX1 concomitant with increased stabilization of β-catenin. ChIP (chromatin immunoprecipitation) studies revealed that β-catenin binds the MSX1 promoter and stabilization of β-catenin elevates MSX1 transcription, indicating that β-catenin works as a transcription co-activator for MSX1. Functionally, exogenous expression of MSX1 in DNAJB6-expressing cells promotes the mesenchymal phenotype by suppression of DKK1. Thus we have identified a novel regulatory mechanism of DNAJB6-mediated DKK1 transcriptional up-regulation that can influence EMT. DKK1 is a feedback regulator of β-catenin levels and thus our studies also define an additional negative control of this β-catenin/DKK1 feedback loop by MSX1, which may potentially contribute to excessive stabilization of β-catenin.

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