Novel WWP2 ubiquitin ligase isoforms as potential prognostic markers and molecular targets in cancer.

Abstract

The WWP2 E3 ubiquitin ligase has previously been shown to regulate TGFβ/Smad signalling activity linked to epithelial-mesenchymal transition (EMT). Whilst inhibitory I-Smad7 was found to be the preferred substrate for full-length WWP2-FL and a WWP2-C isoform, WWP2-FL also formed a stable complex with an N-terminal WWP2 isoform (WWP2-N) in the absence of TGFβ, and rapidly stimulated activating Smad2/3 turnover. Here, using stable knockdown experiments we show that specific depletion of individual WWP2 isoforms impacts differentially on Smad protein levels, and in WWP2-N knockdown cells we unexpectedly find spontaneous expression of the EMT marker vimentin. Re-introduction of WWP2-N into WWP2-N knockout cells also repressed TGFβ-induced vimentin expression. In support of the unique role for WWP2-N in regulating TGFβ/Smad functional activity, we then show that a novel V717M-WWP2 mutant in the MZ7-mel melanoma cell line forms a stable complex with the WWP2-N isoform and promotes EMT by stabilizing Smad3 protein levels. Finally, we report the first analysis of WWP2 expression in cancer cDNA panel arrays using WWP2 isoform-specific probes and identify unique patterns of WWP2 isoform abundance associated with early/advanced disease stages. WWP2-N is significantly downregulated in stage IIIC melanoma and up-regulated in stage II/III prostate cancer, and we also find isolated examples of WWP2-FL and WWP2-C overexpression in early-stage breast cancer. Together, these data suggest that individual WWP2 isoforms, and particularly WWP2-N, could play central roles in tumourigenesis linked to aberrant TGFβ-dependent signalling function, and also have potential as both prognostic markers and molecular therapeutic targets.

• Authors: Surinder M Soond, Paul G Smith, Lloyd Wahl, Tracey E Swingler, Ian M Clark, Andrew M Hemmings, Andrew Chantry
• Journal: Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1832 Issue 12 Pg. 2127-35 (Dec 2013) ISSN: 0006-3002 [Print] Netherlands
• PMID: 23938591 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2013.

Chemical References

• Biomarkers, Tumor
• Protein Isoforms
• RNA, Small Interfering
• SMAD3 protein, human
• Smad3 Protein
• Transforming Growth Factor beta
• Luciferases
• WWP2 protein, human
• Ubiquitin-Protein Ligases

Topics

• Apoptosis
• Biomarkers, Tumor (metabolism)
• Blotting, Western
• Breast Neoplasms (metabolism, pathology)
• Case-Control Studies
• Cell Proliferation
• Epithelial-Mesenchymal Transition
• Female
• Gene Expression Profiling
• Humans
• Immunoprecipitation
• Luciferases (metabolism)
• Male
• Melanoma (metabolism, pathology)
• Neoplasm Staging
• Oligonucleotide Array Sequence Analysis
• Prognosis
• Prostatic Neoplasms (metabolism, pathology)
• Protein Isoforms
• RNA, Small Interfering (genetics)
• Smad3 Protein (metabolism)
• Transforming Growth Factor beta (metabolism)
• Tumor Cells, Cultured
• Ubiquitin-Protein Ligases (antagonists & inhibitors, genetics, metabolism)