title: Imaging analysis of mineralocorticoid receptor and importins in single living cells by using GFP color variants.
abstract: Mineralocorticoid receptor (MR) is a ligand-dependent transcription factor involved in gene regulation in association with another corticosteroid receptor, glucocorticoid receptor. In the absence of ligand, MR resides both in the cytoplasm and in the nucleus. Agonists increase the number of MRs residing in the nucleus. Importins are docking proteins for karyopherin-mediated binding of substrate in a nuclear import pathway. To investigate the interactions between MR and importins, we analyzed the subcellular distribution of MR and importins in response to ligand in living COS-1 cells, which do not express endogenous MR, by using fusion proteins labeled with different spectral variants of green fluorescent protein. In the cells coexpressing fluorescent protein-tagged (FP)-MR and FP-importin alpha, the proteins simultaneously moved into the nucleus from the cytoplasm upon activation with ligand treatment. In the cells coexpressing FP-MR and FP-importin beta, FP-MR moved into the nucleus from the cytoplasm, but the distribution of FP-importin beta was little changed upon ligand treatment. Analysis of a mutant of MR, in which nuclear localization signal (NLS) is inactivated, demonstrated that the intact NLS is necessary for the trafficking of MR related to importin alpha. This is the first visual evidence of the nuclear import of MR in association with importin alpha in single living cells.
authors.affiliation: Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, Kawaramachi Hirokoji, Kamigyo-ku, Kyoto, 602-8566, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Tanaka
authors.forename: Mayumi
authors.initials: M
authors.lastname: Nishi
authors.forename: Masafumi
authors.initials: M
authors.lastname: Morimoto
authors.forename: Tohru
authors.initials: T
authors.lastname: Sugimoto
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kawata
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D002522:Chlorocebus aethiops; D003345:Corticosterone / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics; D008164:Luminescent Proteins / Q000235:genetics; D008856:Microscopy, Fluorescence; D019913:Nuclear Localization Signals / Q000235:genetics; D018161:Receptors, Mineralocorticoid / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D028901:alpha Karyopherins / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C485182:Cyan Fluorescent Protein; D008164:Luminescent Proteins; D019913:Nuclear Localization Signals; D018161:Receptors, Mineralocorticoid; D011993:Recombinant Fusion Proteins; D028901:alpha Karyopherins; D028961:beta Karyopherins; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins; D003345:Corticosterone