Fluorescence Imaging Reveals the Nuclear Behavior of Peroxisome Proliferator-activated Receptor/Retinoid X Receptor Heterodimers in the Absence and Presence of Ligand

In a global approach combining fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), and fluorescence resonance energy transfer (FRET), we address the behavior in living cells of the peroxisome proliferator-activated receptors (PPARs), a family of nuclear re...

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Bibliographic Details
Published in:	The Journal of biological chemistry 2005-05, Vol.280 (18), p.17880-17890
Main Authors:	Feige, Jérôme N., Gelman, Laurent, Tudor, Cicerone, Engelborghs, Yves, Wahli, Walter, Desvergne, Béatrice
Format:	Article
Language:	eng
Subjects:	Active Transport, Cell Nucleus - physiology Animals Cell Nucleus - chemistry Cell Nucleus - metabolism Chlorocebus aethiops COS Cells Fluorescence Resonance Energy Transfer - methods Humans Ligands Peroxisome Proliferator-Activated Receptors - analysis Peroxisome Proliferator-Activated Receptors - metabolism Retinoid X Receptors - analysis Retinoid X Receptors - metabolism
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Summary:	In a global approach combining fluorescence recovery after photobleaching (FRAP), fluorescence correlation spectroscopy (FCS), and fluorescence resonance energy transfer (FRET), we address the behavior in living cells of the peroxisome proliferator-activated receptors (PPARs), a family of nuclear receptors involved in lipid and glucose metabolism, inflammation control, and wound healing. We first demonstrate that unlike several other nuclear receptors, PPARs do not form speckles upon ligand activation. The subnuclear structures that may be observed under some experimental conditions result from overexpression of the protein and our immunolabeling experiments suggest that these structures are subjected to degradation by the proteasome. Interestingly and in contrast to a general assumption, PPARs readily heterodimerize with retinoid X receptor (RXR) in the absence of ligand in living cells. PPAR diffusion coefficients indicate that all the receptors are engaged in complexes of very high molecular masses and/or interact with relatively immobile nuclear components. PPARs are not immobilized by ligand binding. However, they exhibit a ligand-induced reduction of mobility, probably due to enhanced interactions with cofactors and/or chromatin. Our study draws attention to the limitations and pitfalls of fluorescent chimera imaging and demonstrates the usefulness of the combination of FCS, FRAP, and FRET to assess the behavior of nuclear receptors and their mode of action in living cells.
ISSN:	0021-9258 1083-351X