This document discusses prion diseases, which are infectious neurological disorders caused by misfolded prion proteins. It summarizes that prion diseases include Kuru, Creutzfeldt-Jakob disease, and mad cow disease. Prion diseases can be infectious, inherited, or sporadic in origin. The document outlines the differences between normal and misfolded prion proteins and reviews the mechanisms by which misfolded prions are able to induce normal prions to also misfold. It examines the cellular pathways involved in prion propagation and discusses factors that can prevent prion replication.

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-132001, Haryana, India
$Meerut Institute of Engeenering and Technology, Meerut, U.P., India

2. • 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.
INTRODUCTION

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

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 PrP
S S
A
C B

8. ER Golgi
Endosome
Cellular trafficking and cleavage of PrP

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
HSPG
Dependent
binding
domain
Direct binding
domain (aa
161-179)
LRP/LR
PrP
BDI
(aa 144-179)
Heparan sulfate chain
(HS)
Sulfated domains
HSPG
Proteogl
ycan
moiety
GPI
BDII (aa 53-93)

12. Cell Culture Systems for Prion Propagation

13. Sequence of prion protein

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

15. Models for the conversion of PrPc
to PrPsc

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

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.  They generate a C-terminal fragment(C2) which has molecular
weight of 27-30 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
What are Calpains?

23.  It was proposed that prion-associated toxicity involves altered
trafficking of PrP
c
.
 Inhibition of ubiquitin-proteasome system(UPS).
 Deposition of aggresomes of PrP
Sc
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 PrP
c
does not cause cell death.
Tabrizi et al., 2005
Role of Caspases

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

25. Factors Responsible for Prion Propagation cont…
• PrP
c
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. E.g. Hsp70, GroEL
Model for chaperone-supervised PrP conversion

27. 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 PrP
Sc
.
Factors that prevent Prion Replication
Bertsch et al.,2005
Bennion, 2004

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

29. Scrapie BSE
CJD
Kuru
Microscopic changes

30. • 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).
Other microscopic changes

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

32. PrPC
PrPSC
PrPC
Mechanism of plaque formation

33. PrPsc fibrils

34. Plaque

35. Molecular hallmark of the disorder is the accumulation of abnormal prion
protein(PrP
Sc
).
Physiological functions of cellular prion protein (PrP
c
) is not clear.
Identity of intracellular compartment where PrPc
to PrPSc
occurs is not
established.
Prion peptide of 106-126 residues is found to be neurotoxic.
Studies on prion protein will open the avenues for treatment of other
neurodegenerative disorders.
Conclusion