Prions and Protein-Folding Diseases

Question 1

What were the symptoms of Kuru found in the Fore tribe of papau new guinea?

Answer 1

strange walk, slurred speech facial ticks, uncontrollable fits of laugher

death within 6-12 montsh

Question 2

What did brain autopsy of kuru victims reveal?

Answer 2

minimal inflammation, but formation of plaques and spongiform encephalopathy due to neuronal loss

Question 3

How did they ultimately prove that kuru was transmitted via canibalism?

Answer 3

they injected homogenized brain tissue from an individual with kuru directly into the brains of chipanzees
2 years later the first symptoms of kuru were reported and neuropathology revealed kuru in their brains

Question 4

Why did eliminating the practice of cannibalism in the 1960s not completely stop the deaths from kuru immediately?

Answer 4

because there is a really long incubation period for kuru and other prion diseases

Question 5

What are some things prions ar eable to withstand?

Answer 5

30 min boiling, 60 days freezing, chemicals, dessication for 2 years, intense UV exposure, nuclease digestion, small levels of protease

but sensitive to high levels pf protease

Question 6

What is the infectious agent in prion diseases?

Answer 6

a mid folded PrPc protein - PrPsc

it’s capable of inducing the same conformational change in other PrPc proteins

Question 7

what conformational change occurs to form the PrPsc version?

Answer 7

the Helix A alpha helix turns into a beta sheet

Question 8

the conformation change to form PrPsc results in what tertiary structure?

Answer 8

it makes the PrPsc proteins to stick together in amyloid plaques

Question 9

Are all PrPsc proteins in the same strain?

Answer 9

No - there are multiple strains that vary in their infectivity

Question 10

Where is PrPc usually expressed?

Answer 10

It is ubiquitously expressed, but especially in the brain, eyes, spinal cord, skull, vertbral column, tonsils and distal ileum

this is where the PrPsc protein will accumulate the most

Question 11

What two secondary structures can the amyloid form int he brain?

Answer 11

amyloid fibers forming amyloid plaques

Question 12

How can you stain amyloid plaques?

Answer 12

with congo red or thioflavin T dye

Question 13

What cellular repsonse is initiated by the amyloid fibers within the neurons?

Answer 13

triggers the unfolded protein response

this means protein synthesis just shuts down

eventually cell undergoes apotpsosis

Question 14

What are the 5 etiologies of prion diseases we know of in humans?

Answer 14

1. kuru
2. Familial Creutzfeldt-Jakob
3. Sporadic Creutzfeldt-Jakob (etiology unkown - most common)
4. Iatrogenic Creutzfeldt-Jakob (transmitted through cadaver hormones, contaminated surgical equipment, and corneal implants)
5. Variant Creutzfeldt-Jakob (from bovine spongiform encephalopathy)

Question 15

Is familial CJD autosomal dominent or recessive?

Answer 15

dominant

Question 16

In inherited prion diseases, what gene has the mutation?

Answer 16

PRNP gene - encodes for the PrPc

Question 17

In laboratory diagnosis of CJD, what will you see on EEG?

Answer 17

periodic sharp wave complexes

Question 18

in diagnosis of CJD, what will you see in MRI?

Answer 18

high intensity signal in the striatum and linear lesions of the bilateral posterior thalamic nucleus (pulbinar)

Question 19

What will you see in the CSF of CJD

Answer 19

elevation of protein 14-3-3

it’s used as a marker (but also seen in encephalitis and cerebral infarct)

Question 20

What laboratory techniques can you use to diagnose CJD?

Answer 20

1. western blot for the PrPsc protein after proteinase digestion (this actually helps figure out the strain of PrPsc too)

DNA sequenceing for mutations of the PRNP ene

ELISA to detect PrPsc protein in brain tissue

Question 21

How can you test the infectivity of a patient’s PrPsc?

Answer 21

inject it into a mouse and watch

Question 22

What is the current most promising idea for treating prion diseases?

Answer 22

Using a drug to block the phosphorylation of and activation of EIF2-alpha, which is what turns on the unfolded protein response

this means you still get the prion formation, but you keep the cell synthesizing what it needs to survive, so you don’t get the apoptosis and spongiform encephalopathy

Question 23

What non-human prion disease transferred to humans in the early 1990s?

Answer 23

bovine spongiform encephalopathy (mad cow disease) transferred to humans in England - vCJD

Question 24

What are some of the ways vCJD differs from fCJD?

Answer 24

it affects you earlier (28 vs 68)

it takes a little longer to kill you after symptoms (14 mo instead of 5 mo)

Question 25

What is the only evidence we have that chronic wasting disease in deer doesn’t spread to humans?

Answer 25

Intracerebral innoculation of CWD in squirrel monkeys caused the disease, but it didn’t cause the disease in macaques

humans are more closely related to macaques than squirrel monkeys

Question 26

What are some ways we can reduce our risk of getting CWD from deer?

Answer 26

1. don’t eat meat
2. be careful what parts of the meat you do eat
3. don’t feed deer - you don’t want them to congregate and transmit amongst themselves
4. don’t eat sick looking deer

Question 27

What are some diseases associated with NONINFECTIOUS amylokd formation?

Answer 27

Alzheimer’s
Parkinson’s
Type 2 diabetes
Cataracts