title: Characterization of nuclear import of the domain-specific androgen receptor in association with the importin alpha/beta and Ran-guanosine 5'-triphosphate systems.
abstract: Androgen induces androgen receptor (AR) nuclear import, which allows AR to act as a transcriptional factor and ultimately leads to biological activity. However, the mechanism of AR translocation to the nucleus is still unclear. In the present study, we assessed the nuclear import abilities of each domain of AR and their mechanisms related to Ran and importin alpha/beta using green fluorescent protein real-time imaging. The localization of AR to the nucleus in the absence and presence of ligands was dependent upon a complex interplay of the amino terminal transactivation domain (NTD), the DNA binding domain (DBD), and the ligand binding domain (LBD). NTD and DBD showed ligand-independent nuclear import ability, whereas LBD had ligand-dependent transport. In addition, AR deletion mutant lacking DBD was distributed in the cytoplasm regardless of ligand existence, suggesting that the remaining domains, NTD and LBD, are responsible for AR cytoplasmic localization. Cotransfection with a dominant negative form of Ran dramatically inhibited the nuclear import of all AR domains, and a dominant negative form of importin alpha prevented AR and DBD import. Importin beta-knockdown strongly blocked DBD import. These results indicate that there are two additional nuclear localization signals (NLSs) in the NTD and LBD, and there are distinct pathways used to attain domain-specific AR nuclear import: the NLS of DBD is Ran and importin alpha/beta-dependent, whereas the NLSs of NTD and LBD are Ran dependent but importin alpha/beta-independent. Our data suggest that the nuclear import of AR is regulated by the interplay between each domain of the AR.
authors.affiliation: Departments of Anatomy and Neurobiology, Research Institute for Geriatric and Neurobiological Diseases, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Kaku
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Matsuda
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tsujimura
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kawata
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D006801:Humans; D019913:Nuclear Localization Signals / Q000378:metabolism / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011944:Receptors, Androgen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D014018:Tissue Distribution; D014162:Transfection; D028901:alpha Karyopherins / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000378:metabolism*
chemical_list: C410798:AR protein, human; D019913:Nuclear Localization Signals; D011944:Receptors, Androgen; D011994:Recombinant Proteins; D028901:alpha Karyopherins; D028961:beta Karyopherins; D020931:ran GTP-Binding Protein