Novel WWP2 ubiquitin ligase isoforms as potential prognostic markers and molecular targets in cancer.
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.
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
Surinder M
SM
Soond
Paul G
PG
Smith
Lloyd
L
Wahl
Tracey E
TE
Swingler
Ian M
IM
Clark
Andrew M
AM
Hemmings
Andrew
A
Chantry
D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000378:metabolism*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D016022:Case-Control Studies; D049109:Cell Proliferation; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D047468:Immunoprecipitation; D008156:Luciferases / Q000378:metabolism; D008297:Male; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D009367:Neoplasm Staging; D020411:Oligonucleotide Array Sequence Analysis; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000473:pathology; D020033:Protein Isoforms; D034741:RNA, Small Interfering / Q000235:genetics; D051900:Smad3 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014407:Tumor Cells, Cultured; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D014408:Biomarkers, Tumor; D020033:Protein Isoforms; D034741:RNA, Small Interfering; C497790:SMAD3 protein, human; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D008156:Luciferases; C465283:WWP2 protein, human; D044767:Ubiquitin-Protein Ligases
Cancer; EMT; Smads; TGFβ; Transcription; Ubiquitin ligase