HUGE Lecture 19 11/05/26

Where are newly synthesized proteins folded in cells

endoplasmic reticulum

What is the conformation of hydrophobic residues in globular protines

Hydrophobic residues need to be confined in the interior of a globular protein or shielded by interfacing with another protein if exterior facing

What do chaperones do for misfolded proteins

recognize misfolded proteins with hydrophobic patches on exterior and provide space where proteins can attempt to refold correctly

What is the stability of misfolded proteins

often unstable unless aggregated with other misfolded protiens

What happens to stable misfolded proteins

targeted for degradation by ubiquitin proteasome complex

Primary protein structure

sequence of a chain of amino acids

Secondary protein structure

hydrogen bonding of the peptide backbone causes amino acids to fold into repeating pattern

Tertiary protein structure

3-D folding pattern of a protein due to side chain rxns

Quaternary protein structure

protein consisting of more than one amino acid chain

Solubility of misfolded proteins and what it does

toxic conformations are often insoluble and can aggregate with other misfolded proteins

How do misfolded proteins aggregate

via hydrophobic region interactions

Why can aggregation be pathogenic

sequestering a necessary protein away from its normal site of action

What can protein aggregates do to other proteins

may trap proteins within insolubel and protease-resistant aggregates

Inherited prion conditions

effect of the causative variant makes the protein more likely to adopt the abnormally folded state

Non-inherited prion conditions

first abnormally folded molecule arises as a rare chance misfolding of the normal molecule (sporadic)

Infectious prion disease

initial abnormally folded protein molecule arrives externally

What two misfolded proteins cause Alzheimer’s

beta-amyloid and tau

What do misfolded beta-amyloid and tau proteins do to cause alzheimers

form oligomers and fibrils that disrupt normal cellular function and activate inflammatory responses, ultimately resulting in neuronal death and brain damage

Genetic variation in which genes can result in abnormally processed amyloid precursor protein

PSEN1, PSEN2, and APP

What does abnormally processed amyloid precursor protein lead to

production of abnormal amyloid peptides that misfold and aggregate- can trigger tau protein aggregates

What percent of alzheimers disease (AD) are caused by a single genetic mutation

5% (early onset)

What are most AD cases

sporadic disease and later onset

What enzymes cleave amyloid precursor protein

alpha secretase or beta secretase with gamma secretase

What do APP mutations do to beta secretase cleavage activity

increase leading to oligomers aggregating

What is the problem with APP mutations

either too much peptide or altered processing

What does parkinson’s disease result from

interplay of genetic and environmental factors leading to loss of dopaminergic neurons in brain

What does loss of dopamine neurons lead to

irregular brain activity causing movement problems and other symptoms

Hallmark of parkinon’s disease

abnormal levels of aggregated alpha-synuclein protein which form Lewy bodies

How do lewy bodies cause parkinson’s disease

disrupt production and transmission of neurotransmitters in the brain, particularly dopamine (due to neuronal death)

Why may lewy bodies form

when misfolded proteins aggregate exceed the capacity of the ubiquitin proteasome pathway

What can disease tissue do in the brain

spread but in different patterns in different diseases

Kuru disease

prion neurodegenerative disorder resulting in difficulty walking, tremors, and an unsteady gait

What is the brain appearance in kuru disease

holes in brain tissue giving it a songiform appearance

What showed Kuru is a transmissible spongiform encephalopath

Human brain extracts were shown to transfer the disorder to chimpanzees and other primates

What did tribe affected by Kuru do which spread the disease

cannibalized dead relatives

Scrapie

transmissible spongiform encephalopathy in sheep

Primary symptoms of Scrapie

itching, tremors, and lack of coordination

Where did the first cases of mad cow disease originate

UK in 1986 from feed contaminated with a scrapie-like agent

What is mad cow disease

fatal neurological disease with symptoms of aggression and lack of coordination

How is mad cow disease transmitted

consumption of infected meat/feed

What are the two types of mad cow disease

Classical disease- ingestion of affected material

Atypical disease- spontaneous

What are the 3 types of creutzfeldt-jakob disease (human prion disease)

Sporadic

Inherited- genetic

Variant- consumption/ingestion

What are the frequenies of the 3 types of creutzfeldt-jakob disease (human prion disease)

Sporadic- most common 85-90%

Inherited- genetic

Variant- consumption/ingestion

Who discovered the causitive agent of prion disease

Stanley Prusiner who won Novel prize for work on Scrapie in 1997

How did Prusiner find prions

Purified the infectious agent and tested it for susceptibility to treatments prize for his work in 1997 (Scrapie) that destroy proteins or nucleic acids

What does treatment with proteases do to prions

inactivated or reduced infectivity because breaking down proteins

What does treatment with nucleases, UV light, psoralens, hydroxylamine do to prions

no effect

Prion

proteinaceous infectious particle

What does the gene PRNP encode

prion protein

Where is PRNP expressed

in most cells, including brain cells

What is the wild type prion protein

PrPC

PrPC characteristics

soluble and consists of about 40% a helices and has very little beta pleated sheets in its structure

What is the misfolded prion protein called

PrPSc

What does PrPSc do in Scrapie infected brains

aggregated into fibrils consisting of about 45% b pleated sheets and only 30% a helices

What do the aggregated and soluble forms of PRNP share and what is the issue

same amino acid sequence, misfolding is the issue

What is the chain of events of PrPC protein misfolding

PrPC misfolds into PrPSc which can infect other normal PrPC proteins causing them to misfold leading to chain reaction damaging brain tissue

How can prion diseases be diagnosed

sample of brain tissue during biopsy or after death

What are differential drug responses due to

genetic variation or differences in drug metabolism

Pharmacogenetics

focuses on a single genetic marker and how it affects drug response

Pharmacogenomics

focuses on how the genome affects drug response

What aspects of drug action does pharmacogenetic variation affect

• Absorption and distribution

• Metabolic activation

• Effect on target molecule

• Elimination

Pharmacokinetics

what the body does to the drug

Pharmacodynamics

what the drug does to the body

What are the three variants of drug metabolizers

Poor, normal, and ultrafast

What drug dose is needed for poor metabolizers

lower drug dose

What drug dose is needed for normal metabolizers

normal drug dose

What drug dose is needed for ultrafast metabolizers

higher drug dose

What gene family encodes enzymes involved in drug detoxification

Cytochrome P-450

What enzymes are responsible for metabolism of >80% of all commonly used drugs

CYP3A4, CYP2C9, CYP2C19, and CYP2D6

What is warfarin

drug administered to prevent blood clotting

What does warfarin do

competitively inhibits VKOR (vitamin K epoxide reductase)

What does CKOR do

essential for activating available vitamin K

What can overdose of warfarin cause

serious bleeding

Variations in what influence response to warfarin

CYP* and VKOR

Warfarin VKOR CYP pathway

Warfarin inhibits VKOR which usually activates vitamin K that CYP inactivates into hydroxy vitamin K

What is malignant hyperthermia

potentially fatal reaction following exposure to anesthetics or muscle relaxants which trigger a rapid increase in body temperature and muscle breakdown

What variants are the leading cause of malignant hyperthermia susceptibility

RYR1

Is RYR on the ACMG secondary findings gene list and why

yes since its clinically actionable

Type A ADRs (adverse drug reactions)

exaggerated response to a standard dose of a drug, due to genetic variants ● ● that make an individual sensitive

Type B ADRs (adverse drug reactions)

unrelated to the normal action of the drug and are the consequence of some unexpected interaction

Which type of ADR can pharmacogenomic profiling aid in

Type A ADR

Which type are the majority of ADRs

Type A

In what people can warfarin cause excessive bleeding in

people with low-activity CYP or VKOR

What is the pharmacogenomics knowledge base

PharmGKB