title: Nuclear localization signal receptor importin alpha associates with the cytoskeleton.
abstract: Importin alpha is the nuclear localization signal (NLS) receptor that is involved in the nuclear import of proteins containing basic NLSs. Using importin alpha as a tool, we were interested in determining whether the cytoskeleton could function in the transport of NLS-containing proteins from the cytoplasm to the nucleus. Double-labeling immunofluorescence studies showed that most of the cytoplasmic importin alpha coaligned with microtubules and microfilaments in tobacco protoplasts. Treatment of tobacco protoplasts with microtubule- or microfilament-depolymerizing agents disrupted the strands of importin alpha in the cytoplasm, whereas a microtubule-stabilizing agent had no effect. Biochemical analysis showed that importin alpha associated with microtubules and microfilaments in vitro in an NLS-dependent manner. The interaction of importin alpha with the cytoskeleton could be an essential element of protein transport from the cytoplasm to the nucleus in vivo.
authors.affiliation: Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824-1312, USA.
authors.forename: H M
authors.initials: HM
authors.lastname: Smith
authors.forename: N V
authors.initials: NV
authors.lastname: Raikhel
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000595:Amino Acid Sequence; D001693:Biological Transport, Active; D002467:Cell Nucleus / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D028884:Karyopherins; D008870:Microtubules / Q000378:metabolism; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals / Q000235:genetics / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D010947:Plants, Toxic; D011523:Protoplasts / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D028901:alpha Karyopherins
chemical_list: D028884:Karyopherins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D010940:Plant Proteins; D028901:alpha Karyopherins