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What is a Prion?
In its normal state,
prion protein (PrPC, the C stands for Cellular) is a
cell surface glycoprotein present in most mammalian tissues (1).
Its function is not fully determined but evidence suggests it plays
a role in metal homeostasis as it binds copper ions (2).
However, it can accumulate in abnormal forms that cause neurodegenarative
disorders known as transmissible spongiform encephalopathies (TSE),
such as BSE, scrapie and CJD. As well as the accumulation of abnormal
PrP, a key feature of TSEs is their transmissibility. The nature
of the infectious agent is undetermined, but is thought to be the
abnormal form of PrPC, which is known as PrPres, because, unlike
its normal cellular counterpart it is partially resistant to protease
degradation (3). The abnormal
form is also sometimes referred to as PrPSc (scrapie). It has been
proposed that that the abnormal form is infectious because it has
the ability to convert normal PrPC in healthy individuals into the
1. Caughey, B. (2001).
Interactions between prion protein isoforms: the kiss of death?
Trends Biochem. Sci., 26: 235-242
2. Martins, V. R.,
Mercadante, A. F., Cabral, A. L. B., Freitas, A. R. O. and Castro,
R. M. R. P. S. (2001). Insights into the physiological function
of cellular prion protein. Brazilian J. Med. Biol. Res., 34: 585-595.
3. Prusiner, S. B.
(1998). Prions. Proc. Natl. Acad. Sci., USA