Abstract
Retinoid X receptor (RXR) plays a central role in the regulation of intracellular receptor signaling pathways by acting as a ubiquitous heterodimerization partner of many nuclear receptors, including the orphan receptor Nur77 (also known as TR3 [corrected] or NGFI-B), which translocates from the nucleus to mitochondria, where it interacts with Bcl-2 to induce apoptosis. Here, we report that RXRalpha is required for nuclear export and mitochondrial targeting of Nur77 through their unique heterodimerization that is mediated by dimerization interfaces located in their DNA-binding domain. The effects of RXRalpha are attributed to a putative nuclear export sequence (NES) present in its carboxyl-terminal region. RXRalpha ligands suppress NES activity by inducing RXRalpha homodimerization or altering RXRalpha/Nur77 heterodimerization. The RXRalpha NES is also silenced by RXRalpha heterodimerization with retinoic acid receptor or vitamin D receptor. Consistently, we were able to show that the mitochondrial targeting of the RXRalpha/Nur77 heterodimer and its induction of apoptosis are potently inhibited by RXR ligands. Together, our results reveal a novel nongenotropic function of RXRalpha and its involvement in the regulation of the Nur77-dependent apoptotic pathway [corrected]
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Active Transport, Cell Nucleus
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Amino Acid Sequence
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Animals
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Apoptosis / drug effects
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Apoptosis / physiology*
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Base Sequence
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Cell Line
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DNA / genetics
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Dimerization
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Humans
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Mitochondria / metabolism
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Molecular Sequence Data
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Mutation
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Nuclear Receptor Subfamily 4, Group A, Member 1
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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RNA, Small Interfering / genetics
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Receptors, Cytoplasmic and Nuclear
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Receptors, Steroid
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Receptors, Thyroid Hormone / chemistry
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Receptors, Thyroid Hormone / genetics
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Receptors, Thyroid Hormone / metabolism
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Retinoid X Receptor alpha / chemistry
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Retinoid X Receptor alpha / genetics
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Retinoid X Receptor alpha / metabolism*
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Tetradecanoylphorbol Acetate / pharmacology
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Transcription Factors / chemistry
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Transcription Factors / genetics
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Transcription Factors / metabolism*
Substances
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DNA-Binding Proteins
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NR4A1 protein, human
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Nuclear Receptor Subfamily 4, Group A, Member 1
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Proto-Oncogene Proteins c-bcl-2
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RNA, Small Interfering
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Receptors, Cytoplasmic and Nuclear
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Receptors, Steroid
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Receptors, Thyroid Hormone
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Recombinant Fusion Proteins
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Retinoid X Receptor alpha
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Transcription Factors
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DNA
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Tetradecanoylphorbol Acetate