PMID- 12145331
OWN - NLM
STAT- MEDLINE
DCOM- 20030130
LR  - 20220331
IS  - 0888-8809 (Print)
IS  - 0888-8809 (Linking)
VI  - 16
IP  - 8
DP  - 2002 Aug
TI  - Retinoid X receptor dominates the nuclear import and export of the unliganded 
      vitamin D receptor.
PG  - 1738-51
AB  - Liganded and unliganded vitamin D receptors (VDRs) carry out distinct functions; 
      both types of functions require heterodimerization with retinoid X receptors 
      (RXRs). Our recent studies with fluorescent protein chimeras of VDR and RXR, 
      termed GFP-VDR, YFP-RXR, and RXR-BFP, indicated that RXR regulates VDR functions 
      in part by regulating subcellular localization. Here we explored the mechanisms 
      of this regulation. Photobleaching experiments demonstrated that YFP-RXR and both 
      unliganded and liganded GFP-VDR shuttle constantly between nucleus and cytoplasm. 
      To characterize RXR import, we identified a nuclear localization sequence (NLS) 
      in the DNA-binding domain. Mutations in this NLS caused predominant cytoplasmic 
      localization of nlsYFP-RXR and prevented transcriptional activity. The nlsRXR-BFP 
      retained unliganded GFP-VDR in the cytoplasm and reduced baseline transcriptional 
      activity. After calcitriol exposure, however, both GFP-VDR and nlsRXR-BFP entered 
      the nucleus. We characterized receptor export rates and mechanisms using 
      permeabilization experiments. Mutations in the calreticulin binding region slowed 
      both GFP-VDR and YFP-RXR export. Coexpression of RXR-BFP slowed the export of 
      unliganded GFP-VDR, whereas calcitriol treatment tripled the rate of GFP-VDR 
      export. Treatment with leptomycin B, an inhibitor of CRM-1 receptor-mediated 
      export, inhibited export of unliganded GFP-VDR but did not influence export of 
      liganded GFP-VDR or YFP-RXR. Leptomycin B added before calcitriol similarly 
      decreased hormone-induced luciferase activity but was ineffective when added 
      subsequent to calcitriol. These results indicate that the unliganded and liganded 
      VDR interact differently with the import and export receptors and with RXR. Most 
      likely, the regulation of VDR nuclear import by RXR is essential for 
      ligand-independent functions.
FAU - Prufer, Kirsten
AU  - Prufer K
AD  - Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and 
      Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 
      20892, USA.
FAU - Barsony, Julia
AU  - Barsony J
LA  - eng
PT  - Journal Article
PL  - United States
TA  - Mol Endocrinol
JT  - Molecular endocrinology (Baltimore, Md.)
JID - 8801431
RN  - 0 (Calreticulin)
RN  - 0 (Fatty Acids, Unsaturated)
RN  - 0 (Ligands)
RN  - 0 (Luminescent Proteins)
RN  - 0 (Nuclear Localization Signals)
RN  - 0 (Receptors, Calcitriol)
RN  - 0 (Receptors, Retinoic Acid)
RN  - 0 (Recombinant Fusion Proteins)
RN  - 0 (Retinoid X Receptors)
RN  - 0 (Transcription Factors)
RN  - 147336-22-9 (Green Fluorescent Proteins)
RN  - Y031I2N1EO (leptomycin B)
SB  - IM
MH  - Active Transport, Cell Nucleus
MH  - Amino Acid Sequence
MH  - Animals
MH  - Binding Sites/genetics
MH  - COS Cells
MH  - Calreticulin/metabolism
MH  - Fatty Acids, Unsaturated/pharmacology
MH  - Green Fluorescent Proteins
MH  - Humans
MH  - In Vitro Techniques
MH  - Ligands
MH  - Luminescent Proteins/genetics/metabolism
MH  - Molecular Sequence Data
MH  - Nuclear Localization Signals
MH  - Receptors, Calcitriol/genetics/*metabolism
MH  - Receptors, Retinoic Acid/chemistry/genetics/*metabolism
MH  - Recombinant Fusion Proteins/chemistry/genetics/metabolism
MH  - Retinoid X Receptors
MH  - Transcription Factors/chemistry/genetics/*metabolism
MH  - Transcription, Genetic
EDAT- 2002/07/30 10:00
MHDA- 2003/01/31 04:00
CRDT- 2002/07/30 10:00
PHST- 2002/07/30 10:00 [pubmed]
PHST- 2003/01/31 04:00 [medline]
PHST- 2002/07/30 10:00 [entrez]
AID - 10.1210/me.2001-0345 [doi]
PST - ppublish
SO  - Mol Endocrinol. 2002 Aug;16(8):1738-51. doi: 10.1210/me.2001-0345.