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Prions, pronounced “pree-on,” are proteinaceous infectious particles causing transmissible spongiform encephalopathies (TSEs) that affect the central nervous system. They were first studied by British scientist Tikvah Alper in 1967 and later discovered by Stanley B. Prusiner in 1982. Unlike bacteria and viruses, prions do not contain nucleic acids (DNA or RNA) and are highly resistant to environmental factors. Notable prion diseases include Creutzfeldt-Jakob Disease (CJD) in humans and BSE (Mad Cow Disease) in cattle. The mechanism of prion replication remains controversial.
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Introduction to Prions • Pronounced “pree-on” • Shortened term for: Proteinaceous Infections Particle
Introduction to Prions • Pronounced “pree-on” • Shortened term for: Proteinaceous Infections Particle • Causes TSE (Transmissible Spongiform Disease) which attacks the central nervous system (the brain).
Discovery • Study started in 1967 by British scientist, Tikvah Alper, at Hammersmith Hospital in London.
Discovery • Study started in 1967 by British scientist, Tikvah Alper, at Hammersmith Hospital in London. • Discovered by American neurologist, Stanley B. Prusiner, in 1982.
Basic Structure • Normal prions contain about 200-250 amino acids twisted into three telephone chord-like coils known as helices, with tails of more amino acids.
Basic Structure • Normal prions contain about 200-250 amino acids twisted into three telephone chord-like coils known as helices, with tails of more amino acids. • The mutated, and infectious, form is built from the same amino acids but take a different shape. Normal Mutated
Basic Structure • Normal prions contain about 200-250 amino acids twisted into three telephone chord-like coils known as helices, with tails of more amino acids. • The mutated, and infectious, form is built from the same amino acids but take a different shape. • 100 times smaller than the smallest known virus. Normal Mutated
Basic Structure Normal Mutated
Differences From Bactera & Viruses • Prions do not contain nucleic acid; they don’t have DNA or RNA.
Differences From Bactera & Viruses • Prions do not contain nucleic acid; they don’t have DNA or RNA. • They are extremely resistant to heat and chemicals.
Differences From Bactera & Viruses • Prions do not contain nucleic acid; they don’t have DNA or RNA. • They are extremely resistant to heat and chemicals. • Prions are very difficult to decompose biologically; they survive in soil for many years.
Prion Diseases • Humans: CJD (Creutzfeldt Jakob Disease) GSS (Gerstmann Straussler Syndrome)
Prion Diseases • Humans: CJD (Creutzfeldt Jakob Disease) GSS (Gerstmann Straussler Syndrome) • Cattle: BSE (Bovine Spongiform Encephalopathy, better known as Mad Cow Disease)
Prion Diseases • Humans: CJD (Creutzfeldt Jakob Disease) GSS (Gerstmann Straussler Syndrome) • Cattle: BSE (Bovine Spongiform Encephalopathy, better known as Mad Cow Disease) • Sheep: Scrapie • Deer/Elk: CDW (Chronic Wasting Disease)
Controversy • DNA and RNA are the only substances now known to replicate in body tissues, so how do prions make copies of themselves without any nucleic acids?
Controversy • DNA and RNA are the only substances now known to replicate in body tissues, so how do prions make copies of themselves without any nucleic acids? • Some believe TSEs are caused by an unidentified slow-acting virus. • Others believe a small virus accompanies a prion and they work together to cause disease.
