1. PRIONS THE INFECTIOUS PROTEINS
Paras Yadav*, Jaspreet Singh Arora*, Sachinandan De*, Tirtha Kumar Datta*, Surender Lal Goswami*, Aarti Bhardwaj$, Shalini Jain# and Hariom Yadav#
*Animal Biotechnology, #Animal Biochemistry Division, National Dairy Research Institute, Karnal , Haryana, India
$Meerut Institute of Engeenering and Technology, Meerut, U.P., India

2. and changed to prion to sound it rhythmic.
INTRODUCTION
Stanley B. Prusiner coined the term proin from Proteinaceous infective particle
and changed to prion to sound it rhythmic.
Prion diseases were caused by misfolded proteins.
Elucidated the gene and mechanism by which wild type protein bring about the
clinical disease.

3. Prion Diseases Human Animal Kuru Fatal Familial Insomnia (FFI)
Creutzfeldt-Jakob disease (CJD)
Scrapie
Bovine Spongiform Encephalopathy (BSE)
Chronic Wasting Disease (CWD)

4. Classification of prion diseases
Infectious/Exogenous
e.g., Kuru, BSE (mad cow disease), Scrapie
Spread by
Consumption of infected material.
Transfusion.
Sporadic
Familial/Hereditary
Due to autosomal dominant mutation of PrP.

5. Differences between cellular and scrapie proteins
PrPC PrPSC
Solubility
Soluble Non soluble
Structure
Alpha-helical Beta-sheeted
Multimerisation state
Monomeric Multimeric
Infectivity
Non infectious Infectious
Susceptibility to Proteinase K
Susceptible Resistant

6. Steps in the biosynthesis of PrPc

7. Post-translational processing of PrPB

8. Cellular trafficking and cleavage of PrPER
Golgi
Endosome

9. Mechanism of Internalization of PrPC

10. Hypothetical model for a PrPc receptor

11. Model for the function of LRP- LR as the receptor for PrP
BDII (aa 53-93)
Heparan sulfate chain (HS)
BDI
(aa )
HSPG
Dependent binding domain
Direct binding domain (aa )
LRP/LR
Proteoglycan moiety
Sulfated domains
PrP
HSPG
GPI

12. Cell Culture Systems for Prion Propagation

13. Sequence of prion protein

14. Functions of Prion protein
Antioxidative
PrPC + Cu (Copper) 
Antioxidant activity
Resistance to oxidative stress
Prevent neuronal dysfunction
(Brown et al., 2002)
Other functions

15. Models for the conversion of PrPc to PrPsc

16. Time taken for Transformation of mutant PrPc to a PrPSc state
<10 min
BFA
180C
0.5-1 hr
1-6 hr
Synthesis of
Mutant PrPc
Endoplasmic Reticulum
PIPLC-
resistant
Plasma membrane/
Endocytic Pathway
Detergent
insoluble
Protease-
resistant

17. Effect of conformation of PrP on Pro K

18. Model of the cellular pathways
involved in generation of PrPSc

19. Proposed model of PrPc
aggregation and induction of CtmPrP

20. Pathogenesis

21. Mechanism of PrPsc induced apoptosis

22. What are Calpains?
They generate a C-terminal fragment(C2) which has molecular
weight of kDs.
Increase in intracellular levels of Calcium increase
production of terminal fragments .
Calpastatin prevents production of C2.
Inhibitors of lysosomal proteases has no effect on C2
production.
Telling et al.,2004

23. Role of Caspases
It was proposed that prion-associated toxicity involves altered
trafficking of PrPc.
Inhibition of ubiquitin-proteasome system(UPS).
Deposition of aggresomes of PrPSc in nerve cells.
Induction of Apoptosis with activation of Caspase 3 and
Caspase 8.
Complete molecular basis for neuronal death is not known.
Aggregates of over expressed PrPc does not cause cell death.
Tabrizi et al., 2005

24. Factors Responsible for Prion Propagation
The AGAAAAGA Palindrome in Prion Generation
Norstrom & Mastrianni, 2005

25. PrPc association with lipid rafts in the early secretory pathway.
Factors Responsible for Prion Propagation cont…
PrPc association with lipid rafts in the early secretory pathway.
Creutzfeldt–Jakob disease (CJD) in Libyan Jews, linked to the E200K
mutation in PRNP (E200KCJD).

26. Model for chaperone-supervised PrP conversion
E.g. Hsp70, GroEL

27. Factors that prevent Prion Replication
Phospholipase A2 Inhibitors prevent prion replication.
Platelet-activating Factor Antagonists also inhibits prion replication.
Bate et al.,2004
Drugs which share a N-benzylidene-benzohydrazide core structure.
Trimethylamine N-oxide (TMAO), can prevent formation of PrPSc.
Bertsch et al.,2005
Bennion, 2004

28. Gross and Microscopic Changes
Gross changes
Grossly there is Cortical atrophy and ventricular dilatation may also be present.

29. Microscopic changes
Scrapie
BSE
Kuru
CJD

30. Other microscopic changes
Gliosis within plaques.
Loss of oligodendrocytes within plaques.
Axons usually remain intact in plaques.
Both CD4+ and CD8+ lymphocytes are present in active
lesions.
(Kretzschmar et al.,1996, Wilesmith et al., 1997).

31. Diagnosis Diagnosis can be made by: 1. Clinical signs and Symptoms.
Detection of Scrapie
Associated fibrils.
Detection of Abnormal Prion protein (PrPsc) by Western blotting.
4. Two dimensional Gel Electrophoresis Imunodiagnosis of Prion disease.
6. Bioassay in Mice.
Scrapie Associated fibrils.

32. Mechanism of plaque formation
PrPC
PrPC
PrPSC

33. PrPsc fibrils

34. Plaque

35. Conclusion
Molecular hallmark of the disorder is the accumulation of abnormal prion protein(PrPSc).
Physiological functions of cellular prion protein (PrPc) is not clear.
Identity of intracellular compartment where PrPc to PrPSc occurs is not established.
Prion peptide of residues is found to be neurotoxic.
Studies on prion protein will open the avenues for treatment of other neurodegenerative disorders.

36. Thank You