Lecture 13: Protein Misfolding and Disease II

Question 1

How are scrapie (sheep), BSE (bovine), and CJD (humans) characterized?

Answer 1

transmissible spongioform encephalopathies (TSE) (prion diseases)

Question 2

How can CJD be transmitted from humans to primates?

Answer 2

direct implantation of plaque

Question 3

What are found in damaged areas of the brain after death by TSE’s?

Answer 3

amyloid plaques

Question 4

What is the most definitive test for neurodegenerative diseases, such as TSE?

Answer 4

post mortem staining

Question 5

although not the most definitive, what test can be used to detect neurodegenerative diseases?

Answer 5

PET scan

Question 6

What did Prusiner do?

Answer 6

isolate protein which induces prion diseases
discover/isolate PrPc and PrPsc
no nucleic acid

Question 7

What did electron micrographs reveal about TSE?

Answer 7

has islet amyloid polypeptide - organized fibrils

Question 8

How is the infectivity of the TSE infective particle Not reduced? How is reduced?

Answer 8

NOT: conventional methods for sterilization (heat, irradiation)
Reduced: proteins denaturants (NaOH, SDS, guanidine hydrochloride)

Question 9

How are the genetics of fatal familial insomnia and CJD similar?

Answer 9

common primary site mutation

either Met or Val at secondary site

Question 10

How is PrP characterized? Where is it expressed?

Answer 10

glycoprotein

brain, other organs

Question 11

There are two covalently identical forms of PrP. What does this mean?

Answer 11

exact same peptide
different conformations (fold differently)

Question 12

How do PrPsc’s bind to one another? What is this called?

Answer 12

beta sheet

growth

Question 13

When PrPc is converted to PrPsc, adnd several PrPsc molecules bind to one another, what is this called?

Answer 13

nucleation

Question 14

List 4 characterizing features of PrPc

Answer 14

1. non-pathogenic
2. soluble
3. protease sensitive
4. 40% alpha helix, little beta sheet

Question 15

List 4 characterizing features of PrPsc

Answer 15

1. pathogenic
2. insoluble
3. protease insensitive
4. 30% alpha helix, 45% beta sheet

Question 16

There are a few models for amyloid fiber formation. In all of them, what motif is the building block for the amyloid fiber?

Answer 16

beta-helix

Question 17

What technique can be used to silence PrPc? What is the effect in mice?

Answer 17

siRNA silencing to create chimeric mice

survived scrapie infection significantly longer

Question 18

What therapeutic method for TSE is similar to PhiKan083 in p53?

Answer 18

stabilizing PrPc

pull equilibrium away from PrPsc

Question 19

What is the body’s immune response to PrPc and PrPsc?

Answer 19

no immune response

Question 20

What is the downfall to inducing an immune response to PrP?

Answer 20

Not specific to PrPsc - also targets Prpc

Question 21

What is the correct/healthy form of A-beta peptide?

Answer 21

A-beta 40 (cleaved)

Question 22

What is the incorrect form of A-beta peptide? What does it cause?

Answer 22

A-beta 42 (uncleaved)

amyloid plaques –> Alzheimer’s

Question 23

In addition to A-beta 42, what is commonly seen in neurofilbrilliary plaques?

Answer 23

aggregated tau

Question 24

What leads to aggregation of tau?

Answer 24

hyperphosphorylation of tau

Question 25

What single mutation protects against Alzheimer's?

Answer 25

A673T

Question 26

What molecule cleaves A-beta40 --> A-beta42?

Answer 26

gamma secretase

Question 27

What three hypothesies explain the toxicity of amyloid fibrils in Alzheimer's?

Answer 27

mature fibril is toxic pre-fibril is toxic amyloid fibrils are by-product of disease

Question 28

What is the structure of the A-beta amyloid fiber?

Answer 28

parallel, in-register beta sheets

Question 29

What have Alzheimer treatments done? What have they not done?

Answer 29

have decreased A-beta 42 levels | have not improved cognitive ability

Question 30

What happens in late diabetes? What molecule is associated with this?

Answer 30

beta cell crisis due to large scale apoptosis | islet amyloid polypeptide (IAPP)

Question 31

Increased _____ production leads to ______ levels of IAPP

Answer 31

insulin | increased

Question 32

What does IAPP bind? What are these structures known to do?

Answer 32

lipid bilayers | accelerate formation of amyloid fibrils

Question 33

When IAPP is viewed on a ____ wheel, a _____ face is apparent

Answer 33

helical | hydrophobic

Question 34

What is the structure of all amyloid fibers? What two interactions allow their formation?

Answer 34

beta sheets side chain side chain interactions peptide-peptide hydrogen bonds

Question 35

What type of modification blocks growth of amyloid fibers by blocking peptide-peptide h-bonds?

Answer 35

methylation

Question 36

What type of modification blocks growth of amyloid fibers by blocking side chain interactions?

Answer 36

introduce peptide with similar AA sequence | interactions will preferentially form with that peptide, and further growth will be stopped

Question 37

What are the two hypothesis for how soluble oligomers cause death?

Answer 37

pore hypothesis | receptor hypothesis

Question 38

what does the pore hypothesis explain?

Answer 38

curious finding that amyloid fibrils appear to have neutral or protective function in some diseases

Question 39

Which are more toxic: soluble oligomers of IAPP, or mature fibrils?

Answer 39

soluble oligomers