Identification of cryptic nuclear localization signals in the prion protein.
Abnormal transport of C-terminally truncated prion protein (PrP) to the nucleus has been reported in cell models of familial prion disorders associated with a stop codon mutation at residues 145 or 160 of the PrP. In both cases, PrP is translocated to the nucleus in an energy-dependent fashion, implying the presence of cryptic nuclear localization signal(s) in this region of PrP. In this report, we describe the presence of two independent nuclear localization signals (NLS) in the N-terminal domain of PrP that differ in the efficiency of nuclear targeting. When acting independently, each NLS sequence mediates the transport of tagged bovine serum albumin into the nucleus of permeabilized cells. When acting together, the two NLS sequences complement each other in transporting the N-terminal fragment of PrP to the nucleus of transfected cells, where it accumulates at steady state. Interestingly, nuclear translocation of PrP is blocked completely if the N-terminal fragment is extended to include one or two N-glycans. The glycosylated PrP fragment, instead, accumulates in the endoplasmic reticulum. Extension of the N-terminal fragment to include both N-glycans and the glycosyl phosphatidylinositol anchor, as expected, directs PrP to the plasma membrane. These observations hold implications for the pathogenesis of familial prion disorders, where truncated and abnormally glycosylated mutant PrP forms may accumulate in the nucleus and initiate neurotoxicity through novel mechanisms.
Gu
Yaping
Y
The Institute of Pathology, Case Western Reserve University, 2085 Adelbert Road, Cleveland, OH 44106, USA.
Hinnerwisch
Joerg
J
Fredricks
Rebecca
R
Kalepu
Sudheera
S
Mishra
Ravi Shankar
RS
Singh
Neena
N
D021581:Active Transport, Cell Nucleus / Q000235:genetics*; D001921:Brain / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D017096:Prion Diseases / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D011328:Prions / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D014407:Tumor Cells, Cultured
D017261:Glycosylphosphatidylinositols; D010446:Peptide Fragments; D011134:Polysaccharides; D011328:Prions