INTERACTION OF PRION PROTEIN MESSENGER-RNA WITH CBP35 AND OTHER CELLULAR PROTEINS - POSSIBLE IMPLICATIONS FOR PRION REPLICATION AND AGE-DEPENDENT CHANGES

A study of the intracellular distribution of prion protein (PrP) in N( 2)a neuroblastoma cells which had been infected with prions (ScN(2)a c ells) revealed that most PrP is present in the cytoplasm. However, a s ignificant amount of PrP is also present in the nucleus (predominantly in the nucleoli) of these cells, as analyzed by confocal laser scanni ng microscopy. By contrast, no PrP could be detected in the nucleus of uninfected N(2)a cells. The steady-state level of PrP mRNA did not ma rkedly differ between the two cell strains. Likewise, no changes were found in the rate of transcription and in the half-life of PrP mRNA. A number of cellular proteins, among them the nuclear lectin CBP35, was identified that bound to the predicted RNA stem-loop structure of PrP RNA. CBP35 could also be detected in purified infectious prions, sugg esting a possible role in prion replication. Age-dependent studies rev ealed that the content of normal cellular PrP (PrPC) in brain extracts of rats did not change significantly during ageing, while the level o f certain proteins that associate with PrPC mRNA decreases with age. I n addition, we show that rat cortical cells when challenged with infec tious PrP (PrPSc) undergo cell death (apoptosis) in vitro. This delete rious effect was prevented by memantine (1-amino-3,5-dimethyladamantan e) and other blockers of N-methyl-D-aspartate (NMDA) receptor channels . (C) 1997 Elsevier Science Ireland Ltd.