Prion Disease

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Prion Disease

Demenz: Neurobiologische

Grundlagen

Prion Disease as a form of a very special

Dementia

Dr. rer. nat. Frank Baumann


Mink

Encephalopathy

Scrapie (sheep; goat)

Bovine Spongiform

Encephalopathy

(BSE)

Feline

Encephalopathy

Chronic Wasting Disease

of Deer and Elk (CWD)

ANIMALS

PRIONS

HUMANS

Creutzfeldt-Jakob

Disease

(sCJD)

Fatal Familial

Insomnia

Kuru

vCJD;

iCJD

Gerstmann-Sträussler-

Scheinker Disease


Prion diseases: definiton of an infectious disease

Prion diseases are neurodegenerative diseases (spongiosis; gliosis;

PrP deposition) with invariably lethal outcome of the infected host.

Prion diseases are transmissible: An organ homogenate isolated

from an infected host (brain, secondary lymphoid tissues), injected

peripherally or intracerebrally into another host of the same species

or even a different species invariably causes the same disease

(species barrier).

The cellular prion protein is expressed on virtually every cell but to

high degree on cells of the CNS and on cells of the immune system.


„Conventional“ pathogens and infectious proteins

• parasites

• bacteria

• fungi

• viruses

Prions ( -sheet rich proteins)


Koch‘s postulates on

proteinaceous agents

1. The protein must be invariably present in a diseasespecific

form and arrangement in the diseased tissue.

2. The physicochemical characteristics that confer

infectivity on a specific protein must be established.

3. The characteristics that render the host susceptible to

infection by a specific proteinaceous agent must be

established.

4. The disease process must be induced in a susceptible

organism by the pure agent in its infectious form.

5. The protein must be recovered in its infectious form

from the animal that was experimentally infected with

the pure agent.


Definitions of prions, PrP C and PrP Sc

Prion (for proteinaceous, infectious only): Prions are the agents of

transmissible spongiform encephalopathy (TSE), with unconventional

properties, such as resistance to high temperatures, relative high pressure,

formaldehyde treatment or UV-irradiation.

The term “prion” does not have any structural implications other than that a

protein is an essential component of the transmissible agent.

PrP C : The naturally occurring cellular prion protein derived from the prnp

gene.

PrP C in a given cell type is a necessary, but not sufficient for the replication

of prions.

PrP Sc : An abnormal isoform of the mature prnp gene product found in

tissue of TSE sufferers. (1) Partially resistant to digestion by proteinase K,

(2) believed to be conformationally distinct from PrP C and is considered to

be the transmissible agent.

These definitions were adapted from Prof. Adriano Aguzzi and Prof. Charles Weissmann.


The Prion Hypothesis

• Prusiner 1982: the plaque protein is the infectious agent

• Weissmann 1985: The normal, non-infectious protein (PrP C ) is

encoded by the host and is mainly expressed on lymphocytes and

neurons

• The infectious prion protein (PrP Sc ) has the same amino acid

composition, but is resistant to proteases and tends to polymerize

PrP C

Prnp gene

mRNA

normal protein

normal cell

Prnp gene

mRNA

Plaque

infected cell

PrP Sc

infectious

protein


The lipid anchored prion protein PrP C

mouse PrP

Hydrophobicity

4

3

2

1

0

-1

-2

repeats CD

SP CC HC H1 H2 H3

MA

GPI

+

NH 3

-3

-4

1 23 32 64 93 134 191

231 254

amino acid number


PrP C PrP Sc -conversion

+

NH 3

adapted from Stan Prusiner


PrP und seine Isoformen

Primäres

Translationsproduct

22

Signal

Reifung

181 197 231

209 Aminosäuren 23

GPI

CHO CHO

Reifes

PrP C

209 Aminosäuren

PrP C PrP Sc

Konversion (?)

GPI

CHO CHO

PrP Sc PrP 27-30

142 Aminosäuren

209 Aminosäuren

Protease

GPI

CHO CHO

GPI


PrP Sc is Proteinase K resistant

PrP Sc

PrP C

+ Proteinase K

CJD AD CJD


Macroscopic view on Creutzfeldt-Jakob

CJD brain

normal brain


PrP deposition patterns in sCJD

plaque-like synaptic patchyperivacuolar


Spongiosis

Astrogliosis


Human prion diseases

sporadic

Cause unknown

sCJD

80-85%

inherited

Caused by

mutation in PRNP

fCJD

GSS

FFI

10-15%

acquired

Caused by

peripheral uptake

of the agent

vCJD

Kuru

iCJD

~ 160

> 400


Introduction CJD types

CJD is a heterogenous disease subgrouped according to clinical,

neuropathological and genetic data

Molecular characterisation of CJD

1. Codon 129 methionine/valine polymorphism

2. PrP Sc band pattern on WB (Type 1: 21kDa, Type 2: 19 kDa)

different CJD types

codon 129 PrP Sc type leading symptoms PrP Sc deposition in brain

MM/MV 1 dementia, myoclonus, visual disturbances cortex, cerebellum

MM 2

thalamic form:insomnia, dysautonomy ("SFI")

thalamus

cortical form: dementia

cortex (focal), basal ganglia

MV 2 ataxia, extrapyramidal symptoms, dementia

basal ganglia, cortex (focal), thalamus "kuru

plaques" in the cerebellum

VV 1 dementia cortex

VV 2 ataxia, late dementia basal ganglia, thalamus, cerebellum, cortex


Differences between sporadic and variant CJD

sporadic CJD

variant CJD

Age of onset

Initial symptoms

median 65 y

dementia,

visual disturbances

median 29 (19-74) y

sensory, psychiatric

PRNP Genotype

(Codon 129)

83% Met/Met 100% Met/Met

PrP Sc deposition

various deposition

patterns

florid

plaques

Distribution of PrP Sc CNS CNS and lymphoid organs


vCJD

sCJD

vCJD

florid

plaques

panencepahilc

PrP Sc deposition

type 4

glycopattern


iatrogenic CJD

Mode of

infection

No. of

patients

Agent entry into

brain

Median

incubation

period

(range) *

Clinical signs on

presentation

Corneal

3 Optic nerve 16, 18, 320 mo Dementia/cerebellar

transplant**

Stereotactic EEG 2 Intracerebral 16, 20 mo Dementia/cerebellar

Neurosurgery 5 Intracerebral 17 mo (12–28) Visual/dementia

cerebellar

Dura mater graft 114 Cerebral

surface***

6 y (1.5–18) Cerebellar

(visual/dementia)

Growth hormone 139 Hematogenous (?) 12 y (5–30) Cerebellar

Gonadotropin 4 Hematogenous (?) 13 y (12–16) Cerebellar

* Calculated from the midpoint of treatment to the onset of disease.

**One definite, one probable, and one

possible case.

***In two cases, dura was used to embolize vessels of non-CNS tissues, rather than as intracranial grafts.

Brown et. al 2001


Index Patient Patient I Patient II

Zürich,

September 1974

Zürich,

November, 1974

Zürich,

December, 1974

69 ♀ dementia

Implantation of

silver electrodes

for 2 days i.c.

clean.: benzine

desinf.: 70% alcohol

steri.: aldehyde-vapor

23 ♀ epilepsy

Implantation of 9

silver electrodes (2

from index pat.) i.c.

clean.: benzine

desinf.: 70% alcohol

steri.: aldehyde-vapor

17 ♂ epilepsy

Implantation of 9

silver electrodes (2

from pat. 1) i.c.

clean.: benzine

desinf.: 70% alcohol

steri.: aldehyde-vapor

NIH, 1979

Implantation of

electrodes from

index patient in

chimpanzee

18 monthsCJD

Zürich

June, 1976

dementia, (pregnant,

cesarean section),

CJD

Zürich

April, 1976

dementia,

CJD


Variations of the prion hypothesis

Template-directed

refolding

PrP C

PrP Sc

PrP C

PrP Sc

Seeding

(nucleation)

Very,

very slow

Rapid

Rapid


Schematic representation of the protein misfolding

cyclic amplification (PMCA) reaction

Aguzzi, A. et al. Physiol. Rev. 89: 1105-1152 2009; doi:10.1152/physrev.00006.2009


Seeded PrP Sc propagation and Formation of PrP Sc

molecules de novo during serial PMCA propagation of

unseeded purified substrates.

.

Deleault N R et al. PNAS 2007;104:9741-9746


Representation of the three glycosylated PrPSc moieties (un-, mono-, and diglycosylated

PrPSc) in immunoblots of brain extracts after digestion with proteinase K.

Aguzzi A , Calella A M Physiol Rev 2009;89:1105-1152

©2009 by American Physiological Society


The strain phenomenon

PrP Sc

PrP C

PrP Sc

Prion

Strain A

Prion

Strain B

Prion

Strain A

Prion

Strain B


Prion strain „A“

+

Off

state

Prion

state

Strain „B“

Very,

very slow

Rapid

Rapid

+

De novo prion

generation by

nucleation

Seed growth by recruitment of

monomeric precursors

Prion replication

by fragmentation


PrP Sc deposition is strain specific


PK resistance of PrP Sc is specific for

individual strains


Adaptation of prion strains

passage1 passage 2

elk,

Hamster prions

C57BL/6 C57BL/6 C57BL/6

600dpi 300dpi 150dpi


WHAT MAKES A PRION

TOXIC?


Is the endogenous PrP C needed for toxicity:

Grafting embryonic neural tissue into adult host mice

Pregnant wild-type mouse or

overexpressing prnp (tga20)

prnp0/0

prnp tga20

or wt

Embryonic day 12,5

Brandner et al., Nature, 1996


Goals of the Brain Grafting Experiments

• Development of pathological changes in the infected graft ?

• Diffusion or active transport of PrP Sc into the host brain ?

• Reaction of the host brain ?

• Infection of the CNS graft from extracerebral sites ?

• End stage of the disease

in the graft ?

1

3

2


Intracerebral Inoculation of PrP expressing Neurografts

• Grafts develop gliosis &

spongiosis after i.c.

inoculation

Corpus callosum

• PrP Sc plaques form in the

hippocampus of the Prnp o/o

hosts.

Graft

• Prnp o/o hosts do not develop

clinical scrapie.

Lateral ventricle

Sebastian Brandner et al.,

Nature (1996) 379, 339-343


The lipid anchored & the anchorless

prion protein PrP C

+

NH 3

+

NH 3


Pathology of inoculated anchorless PrP mice

Chesebro et al. 2005


Transmission experiment

WT PrP Sc

WT mouse

WT PrP Sc

Time


WT mouse

Plaque loaded dead

Time

PrPs Tg mouse

PrPs Tg mouse

Plaque loaded

clinically healthy

PrP Sc Time


WT mouse

WT mouse

Plaque loaded dead

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