title: Clusterin facilitates COMMD1 and I-kappaB degradation to enhance NF-kappaB activity in prostate cancer cells.
abstract: Secretory clusterin (sCLU) is a stress-activated, cytoprotective chaperone that confers broad-spectrum cancer treatment resistance, and its targeted inhibitor (OGX-011) is currently in phase II trials for prostate, lung, and breast cancer. However, the molecular mechanisms by which sCLU inhibits treatment-induced apoptosis in prostate cancer remain incompletely defined. We report that sCLU increases NF-kappaB nuclear translocation and transcriptional activity by serving as a ubiquitin-binding protein that enhances COMMD1 and I-kappaB proteasomal degradation by interacting with members of the SCF-betaTrCP E3 ligase family. Knockdown of sCLU in prostate cancer cells stabilizes COMMD1 and I-kappaB, thereby sequestrating NF-kappaB in the cytoplasm and decreasing NF-kappaB transcriptional activity. Comparative microarray profiling of sCLU-overexpressing and sCLU-knockdown prostate cancer cells confirmed that the expression of many NF-kappaB-regulated genes positively correlates with sCLU levels. We propose that elevated levels of sCLU promote prostate cancer cell survival by facilitating degradation of COMMD1 and I-kappaB, thereby activating the canonical NF-kappaB pathway.
authors.affiliation: The Vancouver Prostate Centre and Department of Urological Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Amina
authors.initials: A
authors.lastname: Zoubeidi
authors.forename: Susan
authors.initials: S
authors.lastname: Ettinger
authors.forename: Eliana
authors.initials: E
authors.lastname: Beraldi
authors.forename: Boris
authors.initials: B
authors.lastname: Hadaschik
authors.forename: Anousheh
authors.initials: A
authors.lastname: Zardan
authors.forename: Leo W J
authors.initials: LW
authors.lastname: Klomp
authors.forename: Colleen C
authors.initials: CC
authors.lastname: Nelson
authors.forename: Paul S
authors.initials: PS
authors.lastname: Rennie
authors.forename: Martin E
authors.initials: ME
authors.lastname: Gleave
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D051152:Clusterin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000235:genetics; D055550:Protein Stability / Q000187:drug effects; D034741:RNA, Small Interfering / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C480519:COMMD1 protein, human; D002352:Carrier Proteins; D051152:Clusterin; D020672:I-kappa B Proteins; D016328:NF-kappa B; D034741:RNA, Small Interfering; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex