Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cellular isoform of the prion protein (PrPC) is a sialoglycoprotein bound almost exclusively on the external surface of the plasma membrane by a glycosyl phosphatidylinositol anchor. The deduced amino acid sequence of Syrian hamster PrPC identifies two potential sites for the addition of Asn-linked carbohydrates at amino acids 181-183 (Asn-Ile-Thr) and 197-199 (Asn-Phe-Thr). We have altered these sites by replacing the threonine residues with alanine and expressed the mutant proteins transiently in CV1 cells utilizing a mutagenesis vector with the T7 promoter located upstream from the PrP gene. The T7 RNA polymerase was supplied by infection with a recombinant vaccinia virus. The 3 mutant proteins (PrPAla183, PrPAla199 and PrPAla183/199) have a reduced relative molecular weight compared to wild-type (wt) PrP. Deglycosylation as well as synthesis in the presence of tunicamycin reduced the relative molecular weight of all the PrP species to that of the double mutant PrPAla183/199. Our results indicate that both single-site mutant prion proteins are glycosylated at non-mutated sites and they suggest that both potential sites for Asn-linked glycosylation are utilized in wt PrPC. Immunofluorescence studies demonstrate that while wt PrPC localizes to the cell surface, all the mutant PrP molecules accumulate intracellularly. The site of accumulation of PrPAla183 is probably prior to the mid-Golgi stack since this protein does not acquire resistance to endoglycosidase H. Whether the intracellular locations of the mutant PrPC species are the same as those identified for the scrapie isoform of the prion protein (PrPSc) remains to be established.
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PMID:Intracellular accumulation of the cellular prion protein after mutagenesis of its Asn-linked glycosylation sites. 198 82

The expression of osteopontin (OPN) was studied in the brains of mice with scrapie. Reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot analysis showed that the expression of OPN protein and mRNA was increased significantly in the scrapie-infected brains compared to the controls. The increased expression of OPN protein was largely matched with the PrP(Sc) accumulation. Immunohistochemically, OPN was intensely immunostained in neurons of the midbrain at the time of scrapie infection initiation. Particularly, OPN immunostaining was noted in the reactive astrocytes and some microglia in the scrapie brains, while those cells were devoid of OPN immunoreactivity in control brains. Overall, these findings suggest that some neurons affected by PrP(Sc) at an early stage of scrapie transiently express OPN but subsequently succumb to cell death at a later stage of scrapie; astroglial cells after scrapie infection are activated to express OPN; and increased OPN expression in these cells may play an important role in the pathology of scrapie. The precise role of OPN in scrapie needs further study.
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PMID:Increased expression of osteopontin in the brain with scrapie infection. 1641 98