Asparagine-linked Glycosylation of the Scrapie and Cellular Prion Proteins

Arch Biochem Biophys. 1989 Oct;274(1):1-13. doi: 10.1016/0003-9861(89)90409-8.

Abstract

Post-translational modification of the scrapie prion protein (PrP) is thought to account for the unusual features of this protein. Molecular cloning of a PrP cDNA identified two potential Asn-linked glycosylation sites. Both the scrapie (PrPSc) and cellular (PrPC) isoforms were susceptible to digestion by peptide N-glycosidase F (PNGase F) but resistant to endoglycosidase H as measured by migration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. PNGase F digestion of PrPC yielded two proteins of Mr26K and 28K; however, the 26-k species was only a minor component. In contrast, PNGase F digestion of PrPSc yielded equimolar amounts of two proteins of Mr26K and 28K. The significance of this altered stoichiometry between the 26- and 28-kDa deglycosylated forms of PrP during scrapie infection remains to be established. Both isoforms as well as PrP 27-30, which is produced by limited proteolysis of PrPSc, exhibited a reduced number of charge isomers after PNGase F digestion. The molecular weight of PrP 27-30 was reduced from 27K-30K by PNGase F digestion to 20K-22K while anhydrous hydrogen fluoride or trifluoromethanesulfonic acid treatment reduced the molecular weight to 19K-21K and 20K-22K, respectively. Denatured PrP 27-30 was radioiodinated and then assessed for its binding to lectin columns. PrP 27-30 was bound to wheat germ agglutinin (WGA) or lentil lectins and eluted with N-acetylglucosamine or alpha-methyl-mannoside, respectively. Digestion of PrP 27-30 with sialidase prevented its binding to WGA but enhanced its binding to Ricinus communis lectin. These findings argue that PrP 27-30 probably possesses Asn-linked, complex oligosaccharides with terminal sialic acids, penultimate galactoses, and fucose residues attached to the innermost N-acetyl-glucosamine. Whether differences in Asn-linked oligosaccharide structure between PrPC and PrPSc exist and are responsible for the distinct properties displayed by these two isoforms remain to be established.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Asparagine*
  • Brain / metabolism
  • Brain / microbiology
  • Cloning, Molecular
  • Cricetinae
  • DNA, Viral / genetics
  • Electrophoresis, Gel, Two-Dimensional
  • Electrophoresis, Polyacrylamide Gel
  • Glycoside Hydrolases
  • Glycosylation
  • Microsomes / metabolism
  • Microsomes / microbiology
  • Prions / genetics
  • Prions / metabolism*
  • Protein Processing, Post-Translational*
  • Viral Proteins / genetics*
  • Viral Proteins / isolation & purification

Substances

  • DNA, Viral
  • Prions
  • Viral Proteins
  • Asparagine
  • Glycoside Hydrolases