Erioflorin stabilizes the tumor suppressor Pdcd4 by inhibiting its interaction with the E3-ligase β-TrCP1

Loss of the tumor suppressor Pdcd4 was reported for various tumor entities and proposed as a prognostic marker in tumorigenesis. We previously characterized decreased Pdcd4 protein stability in response to mitogenic stim
Loss of the tumor suppressor Pdcd4 was reported for various tumor entities and proposed as a prognostic marker in tumorigenesis. We previously characterized decreased Pdcd4 protein stability in response to mitogenic stimuli, which resulted from p70S6K1-dependent protein phosphorylation, β-TrCP1-mediated ubiquitination, and proteasomal destruction. Following high-throughput screening of natural product extract libraries using a luciferase-based reporter assay to monitor phosphorylation-dependent proteasomal degradation of the tumor suppressor Pdcd4, we succeeded in showing that a crude extract from Eriophyllum lanatum stabilized Pdcd4 from TPA-induced degradation. Erioflorin was identified as the active component and inhibited not only degradation of the Pdcd4-luciferase-based reporter but also of endogenous Pdcd4 at low micromolar concentrations. Mechanistically, erioflorin interfered with the interaction between the E3-ubiquitin ligase β-TrCP1 and Pdcd4 in cell culture and in in vitro binding assays, consequently decreasing ubiquitination and degradation of Pdcd4. Interestingly, while erioflorin stabilized additional β-TrCP-targets (such as IκBα and β-catenin), it did not prevent the degradation of targets of other E3-ubiquitin ligases such as p21 (a Skp2-target) and HIF-1α (a pVHL-target), implying selectivity for β-TrCP. Moreover, erioflorin inhibited the tumor-associated activity of known Pdcd4- and IκBα-regulated αtranscription factors, that is, AP-1 and NF-κB, altered cell cycle progression and suppressed proliferation of various cancer cell lines. Our studies succeeded in identifying erioflorin as a novel Pdcd4 stabilizer that inhibits the interaction of Pdcd4 with the E3-ubiquitin ligase β-TrCP1. Inhibition of E3-ligase/target-protein interactions may offer the possibility to target degradation of specific proteins only as compared to general proteasome inhibition.
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Metadaten
Author:Johanna Blees, Heidi R. Bokesch, Daniela Rübsamen, Kathrin Schulz, Larissa Milke, Magdalena M. Bajer, Kirk R. Gustafson, Curtis J. Henrich, James B. McMahon, Nancy H. Colburn, Tobias Schmid, Bernhard Brüne
URN:urn:nbn:de:hebis:30:3-266847
DOI:http://dx.doi.org/10.1371/journal.pone.0046567
ISSN:1754-6834
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=23056346
Parent Title (English):Plos one
Publisher:PLoS
Place of publication:Lawrence, Kan.
Document Type:Article
Language:English
Date of Publication (online):2012/10/02
Date of first Publication:2012/10/02
Publishing Institution:Univ.-Bibliothek Frankfurt am Main
Release Date:2012/10/09
Volume:7
Issue:(10): e46567
Pagenumber:11
First Page:1
Last Page:11
Institutes:Biochemie und Chemie
Dewey Decimal Classification:570 Biowissenschaften; Biologie
Sammlungen:Universitätspublikationen
Sondersammelgebiets-Volltexte
Licence (German):License LogoCreative Commons - Namensnennung 3.0

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