Over 400 variants of carbohydrate attachment seen possible
Prion mutants linked abnormally to cell membrane
Abnormal proteolytic prion fragment found in CJD brains
Sequence of human prion gene

Diversity of oligosaccharides linked to asparagines of the scrapie prion protein.

Endo T; Groth D; Prusiner SB; Kobata A
Biochemistry 28: 8380-8 (1989)

Prion proteins from humans and rodents contain two consensus sites for asparagine-linked glycosylation near their C-termini. The asparagine-linked oligosaccharides of the scrapie isoform of the hamster prion protein were considered. Structural studies revealed that the outer chain moieties contain a mixture of bi-, tri-, and tetra-antennary complex-type sugar chains with their core:

Man alpha 1--6(GlcNAc beta 1--4)(Man alpha 1--3)Man beta 1--4GlcNAc beta 1--4-(Fuc alpha 1--6)GlcNAc

Variation is produced by the different combination of the oligosaccharides:
Gal beta 1--4GlcNAc beta 1--
Gal beta 1--4(Fuc alpha 1--3)GlcNAc beta 1--
GlcNAc beta 1--, Sia alpha 2--3Gal beta 1--4GlcNAc beta 1--
Sia alpha 2--6Gal beta 1--4GlcNAc beta 1--

When both asparagine-linked consensus sites are glycosylated, the diversity of oligosaccharide structures yields over 400 different forms of the scrapie prion protein. Whether these diverse asparagine-linked oligosaccharides participate in scrapie prion infectivity or modify the function of the cellular prion protein remains to be established.


Mutant prion protein displays an aberrant membrane association in cultured cells

Lehmann S; Harris DA
J Biol Chem 270: 24589-97 (1995)

Inherited forms of prion disease have been linked to mutations in the gene encoding PrP, a neuronal and glial protein that is attached to the plasma membrane by a glycosyl-phosphatidylinositol (GPI) anchor.

One familial form of Creutzfeldt-Jakob disease is associated with a mutant PrP containing six additional octapeptide repeats. We report here our analysis of cultured Chinese hamster ovary cells expressing a murine homologue of this mutant PrP. We find that, like wild-type PrP, the mutant protein is glycosylated, GPI-anchored, and expressed on the cell surface.

Surprisingly, however, cleavage of the GPI anchor using phosphatidylinositol-specific phospholipase C fails to release the mutant PrP from the surface of intact cells, suggesting that it has an additional mode of membrane attachment. The phospholipase-treated protein is still hydrophobic.... Our results suggest that alterations in the membrane association of PrP may be an important feature of prion diseases.


Truncated human prion protein in normal brain and prion diseases

Chen SG; Teplow DB; Parchi P; Teller JK; Gambetti P; Autilio-Gambetti L
J Biol Chem 270: 19173-80 (1995)

The cellular form of the prion protein (PrPc) is a glycoprotein anchored to the cell membrane by a glycosylphosphatidylinositol moiety. An aberrant form of PrPc that is partially resistant to proteases, PrPres, is a hallmark of prion diseases, which in humans include Cruetzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker syndrome, and fatal familial insomnia.

We have characterized the major forms of PrP in normal and pathological human brains. A COOH-terminal fragment of PrPc, designated C1, is abundant in normal and CJD brains as well as in human neuroblastoma cells. Sequence analysis revealed that C1 contains alternative NH2 termini starting at His-111 or Met-112. Like PrPc, C1 is glycosylated, anchored to the cell membrane, and is heat-stable. Consistent with the lack of the NH2-terminal region of PrPc, C1 is more acidic than PrPc and does not bind heparin.

An additional fragment longer than C1, designated C2, is present in substantial amounts in CJD brains. Like PrPres, C2 is resistant to proteases and is detergent-insoluble. Our data indicate that C1 is a major product of normal PrPc metabolism, generated by a cleavage that disrupts the neurotoxic and amyloidogenic region of PrP comprising residues 106-126. This region remains intact in C2, suggesting a role for C2 in prion diseases.


Genomic structure of the human prion protein gene

Puckett,C., Concannon,P., Casey,C. and Hood,L.
Am. J. Hum. Genet. 49 (2), 320-329 (1991)

MANLG CWMLV LFVAT WSDLG LCKKR PKPGG WNTGG SRYPG QGSPG GNRYP PQGGG GWGQP HGGGW GQPHG GGWGQ PHGGG WGQGG GTHSQ WNKPS KPKTN MKHMA GAAAA GAVVG GLGGY MLGSA MSRPI IHFGS DYEDR YYREN MHRYP NQVYY RPMDE YSNQN NFVHD CVNIT IKQHT VTTTT KGENF TETDV KMMER VVEQM CITQY ERESQ AYY