Difference in nucleocytoplasmic shuttling sequences of rat and human constitutive active/androstane receptor

Biochim Biophys Acta. 2007 Jun;1773(6):934-44. doi: 10.1016/j.bbamcr.2007.03.020. Epub 2007 Apr 4.


Fluorescence recovery after photobleaching (FRAP) in spontaneous multinuclear cells shows that both rat and human constitutive active/androstane receptors (CARs) are shuttling proteins with both nuclear localization signals (NLSs) and nuclear export signals (NESs). We previously identified two NLSs in rat CAR: NLS1 in the hinge region (residues 100-108) and NLS2 in the ligand-binding domain (residues 111-320). In the present study, we compared the intracellular localization signals between rat and human CARs. There was a marked difference in their intracellular localization in COS-7 cells because, unlike rat CAR, human CAR does not contain NLS1 due to an amino acid change at position 106. A CRM1-dependent leucine-rich NES, which is sensitive to an inhibitory effect of leptomycin B, was found in the cytoplasmic retention region previously identified within the ligand-binding domain of rat CAR (residues 220-258). We found that human CAR instead has a NES in the ligand-binding domain between residues 170 and 220. Also, we detected CRM1-independent C-terminal NESs between residues 317-358 of rat and human CARs. Removal of NLS1 by N-terminal truncation and mutation of xenochemical response signal caused rat CAR to localize in the cytoplasm of COS-7 cells, which we suspect is due to the masking of NLS2.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus / drug effects
  • Active Transport, Cell Nucleus / genetics
  • Animals
  • Antibiotics, Antineoplastic / pharmacology
  • COS Cells
  • Cell Nucleus / genetics
  • Cell Nucleus / metabolism*
  • Chlorocebus aethiops
  • Cytoplasm / genetics
  • Cytoplasm / metabolism*
  • Fatty Acids, Unsaturated / pharmacology
  • Humans
  • Nuclear Localization Signals / genetics
  • Nuclear Localization Signals / metabolism*
  • Photobleaching
  • Protein Structure, Tertiary / genetics
  • Rats
  • Receptors, Androgen / genetics
  • Receptors, Androgen / metabolism*
  • Species Specificity
  • alpha Karyopherins / genetics
  • alpha Karyopherins / metabolism


  • Antibiotics, Antineoplastic
  • Fatty Acids, Unsaturated
  • Nuclear Localization Signals
  • Receptors, Androgen
  • alpha Karyopherins
  • leptomycin B