The C-terminal globular domain of the prion protein is necessary and sufficient for import into the endoplasmic reticulum.
The mammalian prion protein (PrP) is composed of an unstructured flexible N-terminal region and a C-terminal globular domain. We examined the import of PrP into the endoplasmic reticulum (ER) of neuronal cells and show that information present in the C-terminal globular domain is required for ER import of the N terminus. N-terminal fragments of PrP, devoid of structural domains located in the C terminus, remained in the cytosol with an uncleaved signal peptide and were rapidly degraded by the proteasome. Conversely, the separate C-terminal domain of PrP, comprising the highly ordered helix 2-loop-helix 3 motif, was entirely imported into the ER. As a consequence, two PrP mutants linked to inherited prion disease in humans, PrP-W145Stop and PrP-Q160Stop, were partially retained in the cytosol. The cytosolic fraction was characterized by an uncleaved N-terminal signal peptide and was degraded by the proteasome. Our study identified a new regulatory element in the C-terminal globular domain of PrP necessary and sufficient to promote import of PrP into the ER.
Heske
Johanna
J
Department of Cellular Biochemistry, Max-Planck-Institut für Biochemie, Am Klopferspitz 18, D-82152 Martinsried, Germany.
Heller
Ulrich
U
Winklhofer
Konstanze F
KF
Tatzelt
Jörg
J
D020816:Amino Acid Motifs; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D018388:Codon, Terminator; D003600:Cytosol / Q000378:metabolism; D019286:Endopeptidase K / Q000737:chemistry / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D051379:Mice; D008861:Microsomes / Q000378:metabolism; D009154:Mutation; D011233:Precipitin Tests; D011328:Prions / Q000737:chemistry* / Q000378:metabolism; D014176:Protein Biosynthesis; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D013347:Subcellular Fractions; D013997:Time Factors; D014162:Transfection
D018388:Codon, Terminator; D011328:Prions; D021382:Protein Sorting Signals; D019286:Endopeptidase K