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Prion
diseases are fatal neurodegenerative diseases that include Creutzfeldt-Jacob
disease (CJD) in humans, mad cow disease
in cattle and scrapie in sheep. The infectious
agent in transmissible spongiform encephalopathies is a proteinous infectious
particle or ‘prion’, which is devoid of nucleic acid.
It is believed that these spongiform encephalopathies are caused
by the accumulation of an abnormally folded isoform of the cellular
prion protein (PrPC). This misfolded protein is rich in beta-sheet
and is designated the scrapie isoform, (PrPSc).
The
normal physiological function of the prion protein is yet to be determined.
However, the ability of PrPC to bind Cu2+
in vivo and in vitro suggests a role
in copper homeostasis (Viles, 1999). Indeed, elevated copper levels promote endocytosis of
PrP suggesting that PrP could transport copper into the cell.
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