Structures of the n-linked glycans of the prion protein isolated from murine models of scrapie

Transmissable spongioform encephalopathies are progressive neurogenerative diseases of animals and humans. Conversion of a normal isoform of the plasma membrane protein, PrP, to an aggregated insoluble form (PrP5c) is a key feature of the molecular pathogenesls of these diseases. Many different strains of ageni from natural cases of ovine spongioform encephalopathy have been character ized by their different phenotypes in a panel of inbred mice. Previous studies have shown that the degree of glycosylation varies in different strain models of murine scrapie [1] and it has become essential to gain more information on these carbohydrate structures which may point to cellular or mechanisticorigin of their molecular phenotypes. This study describes the first detailed site-specific characterization of the N-linked carbohydrate structures of PrP's> from murine models of scrapie by mass spectrometry. As over 400 forms of PrP may exist due to the diversity of the glycan moieties, a very sensitive method of detection is required for the identification of every glycoform present. Therefore, structure elucidation was achieved by sequential exoglycosidase digestion of tryptic glycopeptides and analysis by capillary liquid chromatography drc trospray time-of-flight mass spectrometry. Using this method over 70 N-iinked structures were identified on PrP from strain Me7 in Sine mice. Support pro vided by the Ludwig Institute for Cancer Research and the NIH NCRR grant RR01614. [1] R. Somerville, A. Chong, 0. Mulqueen, C. Birkett. S. Wood, .1. Hope (1997) Nature 386, 564.