Prions play a role in both healthy and infected cells

Until Stanley B. Prusiner’s discovery of prions in 1982, it was commonly believed that infections occurred via the transmission of nucleic acids, be it through bacterial or viral particles. Prions, which are now known to cause several neurodegenerative diseases, such as Creutzfeldt-Jakob and mad cow disease, are made up solely of proteins – and are capable of spreading without any DNA or RNA intermediate.

Certain post-translational modifications result in the transformation of normal prion proteins (PrP), which are found in healthy neurons, into abnormal, infectious proteins (PrPSc). These modifications change the proteins’ secondary structure, conferring greater stability and rigidity. Diseased proteins are then capable of influencing the structure of other nearby PrP and converting them into PrPSc mutants. This process may be spontaneous, inherited (through a mutation in the gene encoding the normal protein), or may occur through infectious means (i.e. transplantation). Once the transformation into PrPSc has taken place, the infected prions aggregate inside cells, disrupt cell function, and eventually lead to death.

Prions are resistant to proteases, which break down proteins. They do not act as recognizable antigens, and may therefore go undetected for long periods of time. Many of the diseases they cause (otherwise known as transmissible spongiform encephalopathies) may also lay latent for years, and they are all fatal in humans. Needless to say, our understanding of prions has a long way to go.

The article below discusses studies conducted by Swiss researchers, who are not concerned with the mutant PrPSc, but rather with their healthy predecessor, PrP. Because prions are a relatively new concept in the pathogenic world, these researchers believe that we must first understand their normal function before we can delve into disease.


Reference: Prusiner, Stanley B. “Prions”. PNAS November 10, 1998 vol. 95 no. 23 13363-13383. See also: Prions 'may keep nerves healthy'.

Image credit: Normal prion on left, diseased prion on right. Can be found here.

Linda Le is a contributing writer on biomedical research to TuftScope for Spring 2010.