Cancer Promoted by the Oncoprotein v-ErbA May Be Due to Subcellular Mislocalization of Nuclear Receptors

Department of Biology, College of William and Mary, P.O. Box 8795, Millington Hall 116, Williamsburg, VA 23187-8795, USA.
Molecular Endocrinology (Impact Factor: 4.02). 06/2005; 19(5):1213-30. DOI: 10.1210/me.2004-0204
Source: PubMed


The retroviral v-ErbA oncoprotein is a highly mutated variant of the thyroid hormone receptor alpha (TRalpha), which is unable to bind T(3) and interferes with the action of TRalpha in mammalian and avian cancer cells. v-ErbA dominant-negative activity is attributed to competition with TRalpha for T(3)-responsive DNA elements and/or auxiliary factors involved in the transcriptional regulation of T(3)-responsive genes. However, competition models do not address the altered subcellular localization of v-ErbA and its possible implications in oncogenesis. Here, we report that v-ErbA dimerizes with TRalpha and the retinoid X receptor and sequesters a significant fraction of the two nuclear receptors in the cytoplasm. Recruitment of TRalpha to the cytoplasm by v-ErbA can be partially reversed in the presence of ligand and when chromatin is disrupted by the histone deacetylase inhibitor trichostatin A. These results define a new mode of action of v-ErbA and illustrate the importance of cellular compartmentalization in transcriptional regulation and oncogenesis.

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Available from: Anne Guiochon-Mantel, Aug 22, 2014
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    • "One challenge for the future will be to examine how regulation of this cellular compartmentalization is impaired or altered in the case of aberrant nuclear receptor expression. In addition, defining how nuclear export integrates TRα activity with other signaling pathways may provide important clues as to the mode of action of mutant TRs that are responsible for a host of pathological conditions including cancer (56-58). "
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    ABSTRACT: The thyroid hormone receptor alpha1 (TRalpha) exhibits a dual role as an activator or repressor of its target genes in response to thyroid hormone (T(3)). Previously, we have shown that TRalpha, formerly thought to reside solely in the nucleus bound to DNA, actually shuttles rapidly between the nucleus and cytoplasm. An important aspect of the shuttling activity of TRalpha is its ability to exit the nucleus through the nuclear pore complex. TRalpha export is not sensitive to treatment with the CRM1-specific inhibitor leptomycin B (LMB) in heterokaryon assays, suggesting a role for an export receptor other than CRM1. Here, we have used a combined approach of in vivo fluorescence recovery after photobleaching experiments, in vitro permeabilized cell nuclear export assays, and glutathione S-transferase pull-down assays to investigate the export pathway used by TRalpha. We show that, in addition to shuttling in heterokaryons, TRalpha shuttles rapidly in an unfused monokaryon system as well. Furthermore, our data show that TRalpha directly interacts with calreticulin, and point to the intriguing possibility that TRalpha follows a cooperative export pathway in which both calreticulin and CRM1 play a role in facilitating efficient translocation of TRalpha from the nucleus to cytoplasm.
    Journal of Biological Chemistry 09/2008; 283(37):25576-88. DOI:10.1074/jbc.M710482200 · 4.57 Impact Factor
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    • "Many situations can benefit from quantitative FRET analysis, such as assaying intracellular processes involving lipid rafts and membrane microdomains formation (Kiskowski and Kenworthy, 2007; Rao and Mayor, 2005); activation of signal transduction molecules at specific intracellular locations (Ballestrem et al., 2006; Nakamura et al., 2006); subcellular localization analysis; and the clustering/oligomerization of several membrane proteins, ex. connexins , MHC components, and ER membrane proteins (Bonamy et al., 2005; Di et al., 2005; Herrick-Davis et al., 2004; Pentcheva and Edidin, 2001; Spiliotis et al., 2002; Vamosi et al., 2004). The particular assay presented here showcases the capabilities of quantitative FRET analysis concerning the traYcking of membrane-associated receptor–ligand complexes. "
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    ABSTRACT: Förster resonance energy transfer (FRET) is an effective and high resolution method to monitor protein-protein interactions in live or fixed specimens. FRET can be used to estimate the distance between interacting protein molecules in vivo or in vitro using laser-scanning confocal FRET microscopy. The spectral overlap of donor and acceptor-essential for FRET-also generates a contamination of the FRET signal, which should be removed in order to carry out quantitative data analysis with confidence. Quantitative FRET data analysis addresses the wealth of information contained in the data set, once optimized FRET imaging has been completed. In this chapter, we describe step-by-step what the issues are in quantitative FRET data analysis, using membrane receptor trafficking and organization as an example. The assays described are applicable to many other biological applications.
    Methods in cell biology 02/2008; 89:569-98. · 1.42 Impact Factor
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    • "Indeed, we have observed that v-ErbA is able to modulate the TGF-β signalling pathway in T2ECs (Gonin-Giraud et al., submitted). These data suggest a role for v-ErbA in intracellular signalling pathways in agreement with its cytoplasmic localisation [33]. "
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    ABSTRACT: The v-erbA oncogene, carried by the Avian Erythroblastosis Virus, derives from the c-erbAalpha proto-oncogene that encodes the nuclear receptor for triiodothyronine (T3R). v-ErbA transforms erythroid progenitors in vitro by blocking their differentiation, supposedly by interference with T3R and RAR (Retinoic Acid Receptor). However, v-ErbA target genes involved in its transforming activity still remain to be identified. By using Serial Analysis of Gene Expression (SAGE), we identified 110 genes deregulated by v-ErbA and potentially implicated in the transformation process. Bioinformatic analysis of promoter sequence and transcriptional assays point out a potential role of c-Myb in the v-ErbA effect. Furthermore, grouping of newly identified target genes by function revealed both expected (chromatin/transcription) and unexpected (protein metabolism) functions potentially deregulated by v-ErbA. We then focused our study on 15 of the new v-ErbA target genes and demonstrated by real time PCR that in majority their expression was activated neither by T3, nor RA, nor during differentiation. This was unexpected based upon the previously known role of v-ErbA. This paper suggests the involvement of a wealth of new unanticipated mechanisms of v-ErbA action.
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