Abstract
The toxic proline:arginine (PRn) poly-dipeptide encoded by the (GGGGCC)n repeat expansion in the C9orf72 form of heritable amyotrophic lateral sclerosis (ALS) binds to the central channel of the nuclear pore and inhibits the movement of macromolecules into and out of the nucleus. The PRn poly-dipeptide binds to polymeric forms of the phenylalanine:glycine (FG) repeat domain, which is shared by several proteins of the nuclear pore complex, including those in the central channel. A method of chemical footprinting was used to characterize labile, cross-β polymers formed from the FG domain of the Nup54 protein. Mutations within the footprinted region of Nup54 polymers blocked both polymerization and binding by the PRn poly-dipeptide. The aliphatic alcohol 1,6-hexanediol melted FG domain polymers in vitro and reversed PRn-mediated enhancement of the nuclear pore permeability barrier. These data suggest that toxicity of the PRn poly-dipeptide results in part from its ability to lock the FG repeats of nuclear pore proteins in the polymerized state. Our study offers a mechanistic interpretation of PRn poly-dipeptide toxicity in the context of a prominent form of ALS.
Highlights
The toxic proline:arginine (PRn) poly-dipeptide encoded by the (GGGGCC)n repeat expansion in the C9orf72 form of heritable amyotrophic lateral sclerosis (ALS) binds to the central channel of the nuclear pore and inhibits the movement of macromolecules into and out of the nucleus
Colocalization of the green fluorescent protein (GFP):PR20 fusion protein with labeled wheat germ agglutinin (WGA) suggested that it might be binding to nuclear pores (Fig. S1)
Some envelopes treated with PR20 or WGA were immunostained with an antibody against gp210, a protein known to occupy the periphery of the nuclear pore complex [14]
Summary
The toxic proline:arginine (PRn) poly-dipeptide encoded by the (GGGGCC)n repeat expansion in the C9orf form of heritable amyotrophic lateral sclerosis (ALS) binds to the central channel of the nuclear pore and inhibits the movement of macromolecules into and out of the nucleus. The PRn poly-dipeptide binds to polymeric forms of the phenylalanine:glycine (FG) repeat domain, which is shared by several proteins of the nuclear pore complex, including those in the central channel. The aliphatic alcohol 1,6-hexanediol melted FG domain polymers in vitro and reversed PRn-mediated enhancement of the nuclear pore permeability barrier These data suggest that toxicity of the PRn poly-dipeptide results in part from its ability to lock the FG repeats of nuclear pore proteins in the polymerized state. | | | C9orf repeat expansion PRn poly-dipeptide nuclear pore | FG domain labile cross-β polymers. Prominent among the intracellular targets of these toxic polydipeptides are nucleoporin proteins, including those composed of phenylalanine:glycine (FG) repeats (Nup, Nup, Nup153, and Nup214)
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