Prion

Question 1

How can PrD’s be inherited?

Answer 1

autosomal dominant conditions caused by mutation of the gene encoding prions

Question 2

General secondary structure of PrPsc?

Answer 2

self-propagating fibrillar or amyloid forms of PrP

Question 3

What is PrpSc?

Answer 3

an alternatively folded variant of PrPC, which acts as the infectious agent in PrD’s and is typically protease-resistance (PrPRes)

Question 4

What was PIRIBS derived from?

Answer 4

recombinant PrP rods that are amyloid beta-rich deriving from both spontaneous nucleation (Tycko, 2010) and prion-seeding (Groveman et al., 2014).

Question 5

What do unbranched PrP fibrils satisfy?

Answer 5

key features of PrPRes fibrils

Question 6

What is four rung beta solenoid derived from?

Answer 6

electron crystallography of two-dimensional crystals of N- terminally trunctuated scrapie prion proteins (Wille, 2002) and further supported by X-ray fiber diffraction studies

Question 7

The template assisted model involves

Answer 7

involves the templating of unfolded PrP molecules by inherent structures in PrPSc to mould PrP into PrPSc

Question 8

How do we know that capping leads to propagation?

Answer 8

When these capping structures are eliminated by means of protein-engineering techniques, the resulting “decapped” β-solenoids become unstable and undergo edge-to-edge-driven oligomerization (Bryan et al., 2011).

Question 9

Why is nucleation-fragmentation akin to the growth of crystals?

Answer 9

highly ordered PrPSc oligomers incorporate endogenous PrPC, thereby growing in size. Large PrPSc aggregates may then decay into smaller fragments of various sizes, each of which can restart the nucleation–fragmentation cycle

Question 10

Why is it clear that additional cofactors are involved in prion propagation?

Answer 10

While PrPC is abundantly expressed throughout the body, prion deposition as well as vulnerability to prion toxicity varies profoundly between tissues.

Question 11

Allele frequencies vary between populations

Answer 11

: in the UK, 47% of the healthy population is heterozygous at this locus, and 42% and 11% are homozygous for M and V, respectively (Nurmi et al., 2003)

Question 12

What does homozygosity for either amino acid in codon 129 lead to?

Answer 12

Homozygosity for either amino acid predisposes to spontaneous CJD and leads to an earlier onset of genetic PrD’s (Pocchiari et al.,2004)

Question 13

Why is methionine important?

Answer 13

all but 1 of >300 variant CJD (vCJD) patients identified to date have been homozygous for methionine at codon 129 (Mok et al., 2017)

Question 14

Who showed that 3/4 patients that died from contamination were MM?

Answer 14

Llewelyn et al.,2004; Wroe et al.,2006

Question 15

How did the 4th contaminated individual die and who showed this?

Answer 15

no signs of a neurological disorder and died of a ruptured abdominal aortic aneurysm (Peden et al., 2004).

Question 16

What is the protective effect of MV and VV at 129?

Answer 16

inhibition of homotypic protein–protein interaction, although residue 129 also influences the propagation of particular prion strains via conformational selection

Question 17

Who first found multiple distinct strains through inbred mice?

Answer 17

Multiple distinct strains of scrapie were isolated that can be propagated in lines of inbred mice and distinguished by distinct incubation periods and degree of vacuolation (Fraser and Dickinson, 1973)

Question 18

How do we know these strains aren’t dependent on Prp primary structure?

Answer 18

• These strains cannot be encoded by differences in PrP primary structure because they can be serially propagated in inbred mice with identical PRNP coding sequence

Question 19

Who showed that prion strains could be re-isolated in inbred mice after passage through intermediary species?

Answer 19

Bruce et al., 1994

Question 20

What suggested that prions strains have different conformations?

Answer 20

For two strains of transmissible mink encephalopathy prions, designated hyper (HY) and drowsy (DY) (Bessen et al., 1992), limited proteolysis produced different PrPSc fragment sizes, implying that the two strains have different conformations (Bessen et al., 1994).

Question 21

Who distinguished human prion strains and how?

Answer 21

4 distinct human PrPSc types have been identified by proteolytic fragment size and glycoform ratios following proteinase K digestion, and these are associated with different clinicopathological phenotypes of CJD (Collinge et al., 1996)

Question 22

What did Wadsworth 1999 show?

Answer 22

PrPSc strain types have distinct post-translational modifications leading to distinct metal-ion dependencies

Question 23

What other studies were done to show different conformations of PrPsc strains?

Answer 23

differential proteinase K digestion kinetics; thermal or chaotrope denaturation curves; conformation-dependent immunoassay and infrared spectroscopy (Kuczius, 1999; Safar 1998, 2000) and the use of methods to amplify PrPSc or prions in vitro that show faithful propagation of strain-associated biochemical characteristics (Castilla et al., 2005).

Question 24

How might these strain types relate to codon129?

Answer 24

These characteristics may account for the strain-dependent propagation of prions based on the polymorphism at codon 129 ( PrPsc types 1 + 4 in MM, 2 in all genotypes and 3 in MM or MV)

Question 25

When were antibodies first used for prions?

Answer 25

monoclonal antibodies (mAbs) targeting different domains of PrPC which were found to be protective against PrD in mice nearly 2 decades ago (Heppner et al.,2001).