title: Self-regulated viscous channel in the nuclear pore complex.
abstract: The nuclear pore complex (NPC), the sole gateway for nucleocytoplasmic exchange in eukaryotic cells, allows for the passive diffusion of small molecules and transport-receptor-facilitated translocation of signal-dependent cargo molecules. Whether small molecules passively diffuse through a single central channel or through multiple holes of a hydrogel network is a subject of debate. Additionally, whether the passive and facilitated transport systems occupy distinct or overlapping physical regions of the NPC remains unclear. Here, we directly test these models using three-dimensional super-resolution fluorescence microscopy of human cells. This approach reveals that a single viscous central channel in the NPC acts as the sole pathway for passive diffusion of various small molecules; transport receptors and their cargo complexes take distinct transport routes in the periphery, which is occluded by phenylalanine-glycine filaments. Furthermore, the passive and facilitated passageways in the NPC are closely correlated, and their conformations can be simultaneously regulated by Importin β1 (a major transport receptor) and RanGTP (a critical regulator of transport directionality). These results strongly favor a self-regulated viscous channel configuration in native NPCs over the porous hydrogel meshwork model.
authors.affiliation: Department of Biological Sciences, Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
authors.forename: Jiong
authors.initials: J
authors.lastname: Ma
authors.forename: Alexander
authors.initials: A
authors.lastname: Goryaynov
authors.forename: Ashapurna
authors.initials: A
authors.lastname: Sarma
authors.forename: Weidong
authors.initials: W
authors.lastname: Yang
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence / Q000379:methods*; D008954:Models, Biological; D022022:Nuclear Pore / Q000378:metabolism*; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C424166:KPNB1 protein, human; D008562:Membrane Glycoproteins; C094157:POM121 protein, human; D028961:beta Karyopherins; D049452:Green Fluorescent Proteins; D020931:ran GTP-Binding Protein