Prions
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Viroids
Very small, circular pieces of RNA that are infectious + pathogenic in plants; lack capsids
Prions
Proteinaceous Infective Particles
PrP
Normal mammalian cytoplasmic membrane protein
What is the structure of normal PrP?
Several alpha helices
Prion PrP
Folds into beta-pleated sheets despite having the same amino acid sequence “like an accordion”
What does prion PrP do to normal PrP?
They turn them into beta-sheets (prion protein)
What are prions associated with?
Rare, progressive, neurodegenerative disorders
What are examples of disorders associated with prions?
Mad cow disease (bovine spongiform encephalitis) Scrapie in sheep Chronic wasting disease in deer + elk
Where does prion PrP aggregate?
The brain to form hard, insoluble clumps (amyloid plagues + fibrous structures) • Brain, spinal cord, eyes
How long does it take for symptoms of vCJD to show in humans?
10-20 years
What are examples of symptoms of vCJD?
Depression + anxiety, memory impairment, difficulty walking, confusion, fatigue, difficulty speaking
Sporadic transmission of vCJD
Random misfolding, occurs around age 60
Familial transmission of vCJD
Predisposition to misfolding, DNA-> AA’s
Foodborne transmission of vCJD
Eating infected beef
Medical pathways of transmitting vCJD
Surgery, transplants, transfusions
Variant Creutzfeldt-Jakob (vCJD)
Prion disease in humans
What does prion protein effect?
Lymphoid tissue (spleen, tonsils, appendix, tonsils)
How are prion proteins destroyed?
Incineration, autoclaving in concentrated sodium hydroxide soaking in 2 N NaOH or undiluted sodium hypochlorite for one hour, treating with keratinase + detergent at 100 degrees Celsius