Structure of Prion

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Structure of Prion
The normal prion structure is characterized by
four helices, denoted as PrPc The abnormal one
consist of 2 helices and 4 beta-sheets, which
derived from the two helices of PrPc, is denoted
as PrPse
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The Conversion of PrPc to PrPse
(b)
(a)
Figure 1 Proposed three-dimensional structure
(a) PrPC and (b) PrPSc
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Chain-reaction Conversion of PrPc to PrPsc
PrPc
PrPsc
Chain-reaction Conversion
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How PrPsc attack the Brain?
Brain consists of a mass of nerve tissue (Hundred
billions of neuron) and neuroglia, supporting
neural tissue.
When enough PrPSc proteins have been made they
form long filamentous aggregates that gradually
damage neuronal tissue.
When neuron in the brain are all dead, the
appearance of the brain will become sponge-like
appearance. And this eventually lead to death.
The harmful PrPSc form is very resistant to high
temperatures, UV-irradiation and strong
degradative enzymes.
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Different prions affect different regions of the
brain
Cerebral cortex the symptoms include loss of
memory and mental acuity, also visual imparement
(CJD).
Thalamus Fatal Familial Insomnia (FFI).
Cerebellum lose the control of body movements
and difficulties to walk (kuru, GSS).
Brain stem In the mad cow disease (BSE), the
brain stem is affected.
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Prions infect animals Humans
What are the Prion-Related Diseases?
Are all known prion diseases fatal ?
YES, they are.
where Prion-Related Diseases Occur?
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TSEs
T Transmissible (Communicable) S Spongiform
(Look like sponge) E Encephalopathy (Brain
diseases)
Prion diseases are often called transmissible
spongiform encephalopathies (TSE).
Because after the infection, the brain appearance
become a sponge-like apearance.
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Six forms of TSEs

• CJD - Creutzfeld-Jacob Disease
• BSEs -Bovine-Spongiform-Encephalopathy
• Alper's Syndrome
• GSS - Gerstmann-Straussler-Scheinkner syndrome
• 5) FFI - Fatal Familial Insomnia
• 6) Kuru

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CJD - Creutzfeld-Jakob Disease
The disease causes fatal degradation of brain
tissue and produces a dementia that affects men
and women, often between the ages of 50 and
65.
90 cases progress to death within a year
There is no record of anyone recovering from the
disease and there is no known treatment.
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Causes

• CJD is associated with prions, mutated forms
  of a normal protein produced in nerve cells,
  white blood cells, muscle cells, and the cells of
  many other tissues.
• Just how prions cause the disease symptoms
  remains unclear.
• There are three types of the disease
  sporadic, genetic, and iatrogenic.

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The 3 Type of CJD

• Sporatic CJD Spontaneous mutation. 85 of the
  cases.
• genetic CJD a mutant prion gene is passed
  genetically from one generation to another.
  10-15 of the cases.
• Iatrogenic CJD Contaminated directly to the
  brain (eg Surgery)
• New variant CJD CJD with shorter incubation a
  form of Creutzfeldt-Jakob disease that has a much
  shorter incubation period than previously
  recognized types but is clinically identical. It
  first appeared in the late 1980s.

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BSEs Bovine Spongiform encephalopathy
How Cows are infected?
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BSEWay of infection

The cow eat offal of the infected sheep
Prions are taken up from the gut and transported
along nerve fibers to the brain stem.
Prions accumulate and convert normal prion
proteins to the disease-causing form, PrPSc.
Years later, BSE results when a sufficient number
of nerve cells have become damaged, affecting the
behaviour of the cows. And eventually the cow is
dead.
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Symptom

• Bored with food, tried, unsociable .
• No capability in memorizing anything..
• Loss of control of the muscle movement.
• Can not speak and swallow the food.