Say HELLO to PRIONS!!!

Prions also known as proteinaceous infectious particles are microscopic protein particle but lacking of nucleic acid, transform other normal cellular protein (PrPC) to the prion form PrPSC. Also, thought to be the infectious agent responsible for scrapie and certain other degenerative diseases of the nervous system.

Prion diseases are associated with the conversion of the α-helix rich prion protein (PrPC) into a β-structure-rich insoluble conformer (PrPSc) that is thought to be infectious. Increasingly, PrPSc gets transformed until they completely clogged brain cells. Cells fail to function properly or stop working. Eventually, cells die and release prions into bloodstream to re-infect other cells.

In the picture above, on the left hand side is a normal conformer whereas on the other side is a rogue conformer. PrPSC forms a heterodimer with normal PrPC, then presence of template will alter the protein fold. After which, tightly coiled α-helix will be converted to loose β-sheets.

Prion diseases are often called spongiform encephalopathies due to the post mortem appearance of the brain with large vacuoles in the cortex and cerebellum. They are a family of rare progressive neurodegenerative disorders that affect both humans and animals.
Majority of mammalian species will tend to develop these diseases.

Below are a few examples:

• Scrapie – for sheep
  
• TME (transmissible mink encephalopathy) – for mink


• CWD (chronic wasting disease) – for mule deer, elk
  
• BSE (bovine spongiform encephalopathy) – for cows
  

Humans are also susceptible to several prion diseases:

• CJD - Creutzfeld-Jacob Disease
  
• GSS - Gerstmann-Straussler-Scheinker syndrome
  
• FFI - Fatal familial Insomnia
  
• Kuru


• Alpers Syndrome (in infants)

* More information will be covered on scrapie, BSE and CJD in the next part!!