Single-Molecule Studies of Nucleocytoplasmic Transport: from 1D to 3D

Abstract

Department of Biological Sciences, Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403The nuclear pore complex (NPC), the sole gateway for nucleocytoplasmic exchange in eukaryotic cells, allows for the passive diffusion of small molecules (< 20-40 kDa) and the transport-receptor-facilitated translocation of larger molecules. However, the precise transport mechanism as to how these two transport modes pave their pathways through the NPC remains in dispute among numerous transport models. By a newly developed single-molecule speedy microscopy and a deconvolution algorithm, we advanced the single-molecule imaging of nucleocytoplasmic transport from 1D (one-dimension) to 3D. The 3D routes for both passive and facilitated transport through human NPCs under real-time trafficking conditions have been obtained with a spatial resolution of 9 nm at 400 μs. Our data strongly support a transport mechanism in which transport receptors or transport-receptor-cargo complexes pave their pathways by interacting with the FG repeats at the periphery around a single primary central axial channel for passive diffusion of small molecules.