Definition Prions and Protein misfolding Diseases: Alzheimer’s disease, Creutzfeld-Jakob disease

Prions: Prion protein was actually an internal coded protein by PRNP gene

• Normal gene forms a protein PrP^c (prion protein cellular) which is distributed on the nerve cell surface
• The infectious counterpart PrP^sc(prion protein scrapie) protein accumulates within nerve cells and ultimately kill neurons.
• Both these protein forms have identical amino acid but they differ in the way the polypeptide chain folds to form the 3D functional protein molecule. PrP^sc is highly stable, insoluble and protease insensitive and composed of β sheets  compared to PrP^c  which is protease sensitive and entirely of α helical segments. 
• Prions also cause other neurological diseases such as Kuru and Gerstmann-Strausler-Sheinker syndrome.

Alzheimer’s disease

1.Alzheimer’s disease (AD)

• non transmissable          
• CJD and AD are very similar and both are fatal degenerative diseases resulting memory loss, confusion loss of reasoning.
• Why AD?
• Is due to fibrillar deposits of insoluble materials called Amyloid
• Amyloid is due to self association of polypeptide composed predominantly of β sheets
• AD: caused by A β peptide from APP gene. (amyloid precursor protein).
• Vaccination for AD: APP vaccination (A β42 peptide injection).

More about, Alzheimer’s disease

2.CJD (Creutzfeld-Jakob disease)

• a neurodegenerative disease
• The causative organism remained a mystery for a long time until Stanley Prusiner discovered the unexpected proteinaceous infectious particles, the prions.

Key terms:

Domains: A part of protein with more than few hundred amino acid that can fold and function independently from rest of protein and may exist in different protein.

Practice Questions:

1.Among the following examples, ----- alone share properties of Chaperones. 

 A) Virus 

B) Prion 

C) Viroid 

D) Retrovirus

Ans: B) Prion