title: Nuclear import of the thyroid hormone receptor α1 is mediated by importin 7, importin β1, and adaptor importin α1.
abstract: The thyroid hormone receptor α1 (TRα1) is a nuclear receptor for thyroid hormone that shuttles rapidly between the nucleus and cytoplasm. Our prior studies showed that nuclear import of TRα1 is directed by two nuclear localization signals, one in the N-terminal A/B domain and the other in the hinge domain. Here, we showed using in vitro nuclear import assays that TRα1 nuclear localization is temperature and energy-dependent and can be reconstituted by the addition of cytosol. In HeLa cells expressing green fluorescent protein (GFP)-tagged TRα1, knockdown of importin 7, importin β1 and importin α1 by RNA interference, or treatment with an importin β1-specific inhibitor, significantly reduced nuclear localization of TRα1, while knockdown of other importins had no effect. Coimmunoprecipitation assays confirmed that TRα1 interacts with importin 7, as well as importin β1 and the adapter importin α1, suggesting that TRα1 trafficking into the nucleus is mediated by two distinct pathways.
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Vincent R
authors.initials: VR
authors.lastname: Roggero
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Jibo
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Parente
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Yazdi
authors.initials: Y
authors.lastname: Doshi
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Rose C
authors.initials: RC
authors.lastname: Dziedzic
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Emma L
authors.initials: EL
authors.lastname: McGregor
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Arev D
authors.initials: AD
authors.lastname: Varjabedian
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Sara E
authors.initials: SE
authors.lastname: Schad
authors.affiliation: Department of Biological Sciences, Hampton University, Hampton, VA, 23668, USA.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Bondzi
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, VA, 23185, USA. Electronic address: laalli@wm.edu.
authors.forename: Lizabeth A
authors.initials: LA
authors.lastname: Allison
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000378:metabolism*; D021381:Protein Transport; D011799:Quinazolines / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013696:Temperature; D037021:Thyroid Hormone Receptors alpha / Q000378:metabolism*; D028901:alpha Karyopherins / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*
chemical_list: C466996:IPO7 protein, human; C424166:KPNB1 protein, human; D028884:Karyopherins; D011799:Quinazolines; D018160:Receptors, Cytoplasmic and Nuclear; D037021:Thyroid Hormone Receptors alpha; D028901:alpha Karyopherins; D028961:beta Karyopherins; C568452:importazole; C087978:karyopherin alpha 2
keywords: Importin; Nuclear import; Thyroid hormone; Thyroid hormone receptor