Cell-penetrating peptides (CPPs) including arginine-rich peptides are attracting a lot of attention due to their potential as a novel intracellular drug delivery tool without substantial toxicity. On the other hand， disease-associated arginine-rich CPPs， such as poly-PR and poly-GR translated from C9orf72 gene， also efficiently enter neuronal cells and then kill them. Although both non-harmful CPPs and harmful poly-PR/GR penetrate the plasma membrane using same arginine residues， little is known about the factors which determine the toxicity of the pathogenic CPPs. Here， we show that poly-PR and poly-GR， but not other Arg-rich CPPs， specifically distributed to nucleolus via interaction with RNA. I... More
Cell-penetrating peptides (CPPs) including arginine-rich peptides are attracting a lot of attention due to their potential as a novel intracellular drug delivery tool without substantial toxicity. On the other hand， disease-associated arginine-rich CPPs， such as poly-PR and poly-GR translated from C9orf72 gene， also efficiently enter neuronal cells and then kill them. Although both non-harmful CPPs and harmful poly-PR/GR penetrate the plasma membrane using same arginine residues， little is known about the factors which determine the toxicity of the pathogenic CPPs. Here， we show that poly-PR and poly-GR， but not other Arg-rich CPPs， specifically distributed to nucleolus via interaction with RNA. Importantly， C9orf72-dipeptides， but not other Arg-rich CPPs， caused inhibition of protein translation and cell death. Raising extracellular pH enhanced the cell penetration of poly-PR. The repeat number of (PR) affected the secondary structure and determined the intracellular delivery rate and neurotoxicity， and enforced intracellular delivery of non-penetrating short poly-PR peptide caused cell death， suggesting that modulation of extracellular environment to inhibit the uptake of Arg-rich dipeptides might be a drug target against poly-PR/GR-mediated neurotoxicity.
