Sugar modifications and transport proteins keep nuclear pores mobile
Experiments in living cells examined how the protein barrier inside nuclear pores stays mobile while controlling passage. A peer-reviewed study found that sugar modifications and transport proteins together brought a reconstructed barrier closer to its behaviour in cells. Blocking the sugar-adding enzyme slowed nuclear import, and increasing transport proteins partly restored it.
Science··Midday
Living pores retain a mobile protein barrier
Researchers measured protein motion in the nuclear pores of living cells. These pores regulate passage into and out of the cell nucleus. The peer-reviewed experiments examined the selective barrier formed by mobile protein regions inside them.[1], [2]
The barrier contains regions rich in the amino acids phenylalanine and glycine, abbreviated FG. Researchers placed fluorescent dyes at fifteen positions in NUP98, a protein in this barrier. Changes in light polarization indicated how its segments moved in living cells. Apparent movement times of around 57–108 nanoseconds were model-based estimates, as the fluorescent dye's lifetime is shorter than these slow motions.[1]
Sugar and transport proteins alter the network
Outside cells, prepared protein condensates could develop more solid, amyloid-like hydrogel properties within about an hour. Living nuclear pores retained mobility over two hours of observation. Combining the sugar modification called O-GlcNAc with importin beta, a transport protein, brought a reconstructed barrier closer to the mobility profile measured in cells. Neither factor alone reproduced the entire profile.[1]
Blocking the enzyme that adds the sugar modification slowed nuclear import in living cells. Increasing the amount of importin partly restored transport. These interventions compared the behaviour of an isolated protein network with the combined influence of chemical modification and transport receptors in the cell.[1]
Transport proteins concentrate near the pore edge
Molecular dynamics simulations proposed that importins concentrate toward the pore's edge while FG chains extend toward its centre. Imaging in fixed cells also supported peripheral enrichment. The simulations did not reproduce every measured density, and the findings do not establish an entirely empty central channel. The experiments investigated cell transport and protein mobility, rather than clinical outcomes in people.[1]
