Prions

Prion Characteristics and Transmission

Prions are proteinaceous infectious agents that cause fatal neurological diseases. They can be transmitted by inoculation or through the alimentary route, affecting not only the same species but also different species, including humans. Normally, the prion protein is a self-duplicating transmembrane glycoprotein, labeled as PrPC, and its isoform (mutant) is PrPSC.

PrPC Structure

PrPC is a glycoprotein with 709 amino acid residues and a molecular weight of 33,000-35,000. Sialic acid attaches to residues 181-197 of asparagine. There are two disulfide bonds: Cys-179 and Cys-214, and the structure contains copper. Both prions PrPC and PrPSC are encoded by the same chromosome gene. During translation, a structure of 254 amino acid residues forms, which later decreases to 209 amino acid residues.

PrPSC Formation

After the translation of the polypeptide PrPC, a helix forms, binding to the cell membrane. In contrast, mutant forms of the protein (PrPSC) develop structures resistant to detergents and proteases and form insoluble deposits similar to amyloids. These mutant prions form conglomerates in the form of rods and ribbons (25-550 nm). They resist boiling, ultraviolet radiation, 70% ethanol, and formaldehyde and remain in tissues fixed with a 10% formalin solution.

Pathological Protein Conformations

When entering the body, pathological prions lead to the accumulation of amyloid-like structures, incorporating normal PrPC proteins. Prions can multiply and evolve, even without RNA or DNA. In mammals, including humans, an active PrPC protein is present on the 20th chromosome.

Impact on Health

Transmissible spongiform encephalopathies and neurodegenerative brain disorders affect both humans and animals. Age-related dementia, some types of Alzheimer’s disease, and Kuru disease may result from changes in prion proteins in the brain.

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė