1. CLINICAL ASPECTS OF BIOCHEMISTRY NEURODEGENERATIVE DISEASES Prion diseases Alzheimer's disease

2. SOME PRION DISEASES TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES SpeciesTransmission ScrapieSheepInfection Bovine spongiform encephalopathy (BSE) CowInfection (contaminated feed) KuruHumanInfection (cannibalism) Creutzfeldt-Jakob disease Iatrogenic Familial Sporadic New variant Human Infection (growth hormone etc.) Germline mutations of PrP gene Somatic mutations of PrP gene or spontaneous conversion Infection (eating beef?) Gertmann-Straussler- Scheinker disease (GSS) humanGermline mutations of PrP gene Fatal familial insomnia (FFI)HumanGermline mutations of PrP gene

3. SPONGIFORM BRAIN TISSUE From Prusiner (1998)

4. HOW CAN PROTEINACEOUS PARTICLE BE INFECTIOUS? (a)May contain "shielded" nucleic acid? (b)Proteins specify own aa sequence? (c)Normal cells carry a gene that encodes PrP, and the product is changed to a different conformation by the infectious particle?

5. THE PRION HYPOTHESIS TSEs occur when the normal ‘cellular’ form of the prion protein (PrP c ) is converted to the abnormal form (PrP sc ). PrP c and PrP sc differ in conformation. The conversion is ‘autocatalytic’ - PrP sc facilitates the conversion of more PrP c to PrP sc.

6. 1. The nature of PrP c and PrP sc 2.Conversion of PrP c to PrP sc 3.Inherited TSEs 4.Species specificity and species barriers 5.Strains 6.Normal function; role in disease 7.Doppel 8.BSE and nvCJD 9.Therapies? TSEs - MAIN TOPICS

7. Normal (PrP c ) and abnormal (PrP s ) forms of prion protein PrP c Precursor ~ 250 amino acids. Mature PrP c ~ 210 aas Hydrophobic glycoprotein GPI anchor (glucosyl phosphatidyl inositol) NMR structure - C-terminal end  -helical, N-terminal end unordered PrP sc Same sequence and postranslational modifications as PrP c Different conformation - more  -sheet Tends to form insoluble aggregates More resistant to proteolysis than PrP c Insoluble PrP sc ( in amyloid plaques) not infectious?

8. PrP C PrP Sc PrP C PrP Sc -PK +PK PrP Sc IS RESISTANT TO PROTEOLYSIS Based on Priola (2001)

9. STRUCTURE OF THE HUMAN PRION PROTEIN Globular domain Based on Rivera-Milla et al (2003)

10. HYPOTHETICAL MODELS FOR PrP c AND PrP sc Based on Prusiner (1998)

11. beta sheet alpha helix

12. PrP Sc CAN CONVERT PrP C TO PrP Sc IN VITRO Based on Priola (2001)

13. TWO MODELS FOR CONVERSION OF PrP C TO PrP Sc (a) PrP C PrP Sc (b) Etc ~6 Very slowfast

14. INHERITED FORMS OF CJD, GSS, FFI etc Mutations may stabilise PrP sc conformation e.g. P102L in GSS [when this was engineered into mice they developed 'scrapie') Met/Val 129 polymorphism in man - Val homozygotes more susceptible to CJD? Met homozygotes more susceptible to nvCJD?

15. SOME POINT MUTATIONS IN THE PrP GENE THAT CAUSE HUMAN PRION DISEASE PositionNormalMutant 102ProLeu 105ProLeu 145AlaStop 178AspAsn 180ValIle 200GluLys Based on Priola (2001)

16. SPECIES BARRIERS TO TRANSFER OF PrP Sc Sequence differences between PrP from different species may provide (and explain?) some barrier to infection - but incomplete. E.g. Mouse  mouse transfer gives more rapid infection than mouse  hamster etc. But, mouse  hamster  hamster gives faster infection, Homologous PrP Sc is better at converting PrP C than heterologous

17. STRAINS OF PRION DISEASES Scrapie occurs as about 20 different strains (differentiated by time taken to infect mice and different behavioural effects). CJD occurs as 2-4 different strains. BSE only one. May be explicable in terms of different conformations, but the more strains the more far-fetched this explanation. The biggest problem with the Prusiner model? For 2 CJD strains - evidence for different conformations (pattern of proteolysis)

18. DIFFERENT PrP Sc STRAINS - DIFFERENT CONFORMATIONS Based on Priola (2001) -PK +PK

19. WHY DOES PrP Sc CAUSE DISEASE? Possible explanations include: Neurotoxic Deposits disrupt cells Deposits disrupt intercellular contacts (synapses etc) Loss of PrP C NORMAL FUNCTION OF PRP C Not clear; knockout mice lacking PrP are not seriously abnormal Possible roles in cell signalling and in processing copper ions have been suggested

20. DOPPEL (Dpl) A PrP-like protein (~25% sequence identity but shorter). Gene close to PrP gene - could explain variable effect of PrP knockouts Involvement in prion diseases? Based on Behrens & Aguzzi (2002)

21. ANNUAL INCIDENCE OF BSE IN THE UK 40,000 30,000 20,000 10,000 Number of BSE cases 858687888990919293949596 16 83663 Year of epidemic

22. nvCJD incidence 0 5 10 15 20 25 30 199419951996199719981999 20002001200220032004

23. nvCJD incidence 0 5 10 15 20 25 30 199419951996199719981999 20002001200220032004 40,000 30,000 20,000 10,000 Number of BSE cases 858687888990919293949596 Year of epidemic

24. CJD - POSSIBLE THERAPIES Drugs that stabilise PrP C (stabilise helical conformation) Drugs that inhibit aggregation & amyloid (  sheet) formation Immunization against PrP C or PrP Sc