Importin-β modulates the permeability of the nuclear pore complex in a Ran-dependent manner.
Soluble karyopherins of the importin-β (impβ) family use RanGTP to transport cargos directionally through the nuclear pore complex (NPC). Whether impβ or RanGTP regulate the permeability of the NPC itself has been unknown. In this study, we identify a stable pool of impβ at the NPC. A subpopulation of this pool is rapidly turned-over by RanGTP, likely at Nup153. Impβ, but not transportin-1 (TRN1), alters the pore's permeability in a Ran-dependent manner, suggesting that impβ is a functional component of the NPC. Upon reduction of Nup153 levels, inert cargos more readily equilibrate across the NPC yet active transport is impaired. When purified impβ or TRN1 are mixed with Nup153 in vitro, higher-order, multivalent complexes form. RanGTP dissolves the impβ•Nup153 complexes but not those of TRN1•Nup153. We propose that impβ and Nup153 interact at the NPC's nuclear face to form a Ran-regulated mesh that modulates NPC permeability.
Institute for Structural and Molecular Biology, University College London and Birkbeck College, London, United Kingdom.
Alan R
AR
Lowe
Department of Physics, University of California, Berkeley, Berkeley, United States.
Jeffrey H
JH
Tang
Department of Physics, University of California, Berkeley, Berkeley, United States.
Jaime
J
Yassif
Section of Life Sciences and Technologies, École polytechnique fédérale de Lausanne, Lausanne, Switzerland.
Michael
M
Graf
Department of Chemistry, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
William Y C
WY
Huang
QB3, University of California, Berkeley, Berkeley, United States.
Jay T
JT
Groves
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.
Karsten
http://orcid.org/0000-0001-7224-925X
K
Weis
Department of Physics, University of California, Berkeley, Berkeley, United States.
Jan T
JT
Liphardt
D021581:Active Transport, Cell Nucleus; D036681:Fluorescence Recovery After Photobleaching; D006367:HeLa Cells; D006801:Humans; D018613:Microscopy, Confocal; D008954:Models, Biological; D022022:Nuclear Pore / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism*; D010539:Permeability; D034622:RNA Interference; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
C079377:NUP153 protein, human; D028861:Nuclear Pore Complex Proteins; C108121:TNPO1 protein, human; D028961:beta Karyopherins; D020931:ran GTP-Binding Protein
biophysics; cell biology; human; importin-beta; nuclear pore complex; ran; structural biology; super-resolution microscopy