1. Investigations into Prionic Mutations Mutated Prion Protein (PrPSc)
Advisor: Jamie Allison, Loveland High School
Mentor: Rajiv Soman, PhD, University of Cincinnati
Presenter: Jacquelyn Pohl
Basics
Theoretic Application
Background: All of the epidemics that have affected the world’s population whether it was cancer, HPV or AIDS, have not been given a cure or prevention. Epidemics happen each day world wide. The medical facilities are ready for mild outbreaks with containment centers available, however, barely anything is known in regards to what the next big epidemic will be. There were all these pandemics and it is believed that mutated protein will be the next epidemic.
Amino Acids are the building blocks for protein.
Diseases Caused:
Creutzfeldt-Jakob Disease
Kuru
Fatal Familial Insomnia
Gerstmann-Sträussler-Scheinker Disease
BSE – “Mad Cow Disease”
Scrapie
Abstract: Prions are mutated proteins and proteins are organic compounds composed of amino acids. PrPC which is the cellular version of the prion protein is located in practically all tissue in the human body however PrPSc which is the mutated version of PrPC is found solely in the brain. One theorized function of PrPC is copper mediation where as no beneficial function has been found for PrPSc. PrPSc is an infectious agent that causes many diseases based on the mutation of its amino acid sequence. It causes rapid degradation of the brain. PrPC is easily destroyed where as PrPSc is virtually indestructible. PrPC has an octarepeat region which consists of 32 amino acids. PrPC also has a cystine/cystine disulfide bond. The mutation involves the folding of the protein from one form into another. Little is known about how this mutation occurs and why it occurs. What mechanism or mechanisms are allowing this mutation to occur and how does it get started? Are there any possible solutions to end this mutation or disease?
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Peptide bonds are the formation of bonds between amino acids that form the secondary structure of protein.
Disease Focus: Creutzfeldt-Jakob (CJD)
Rare, degenerative rapid brain disorder
Three types:
Sporadic: isolated occurrence
Inherited: genetic
Acquired: from outside body/system
Symptoms: dizziness, dysarthria, myoclonus, ataxia, dementia, and death
No treatment or diagnosis until autopsy
Prion Protein (PrPC)
Mutated Prion Protein (PrPSc)
Function Theories:
Copper Mediation: Copper ion regulation in the tissues of the pre-synaptic membrane of the brain. This process delivers copper (II) ions to neurons.
Bone Marrow Renewal: PrPC is located on the surface of hemotopoietic stem cells as indicators that the cells will most likely become adult blood cells. Contribution to the renewal of these cells is certain however the mechanism is unknown.
Involvement in Synaptic Transmission of Calcium: Loss of PrPC causes a disturbance in neuronal calcium homeostasis. It affects the calcium (II) ions release from the internal endoplasmic reticulum. This is critical because of the signaling pathways that lead to structural and functional changes in neurons.
Protective Properties in Response to Oxidative Stress: PrPC helps stabilize neurons because lack of PrPC causes hypersensitivity of neurons to oxidation. O2 can act as an acid or base so copper (II) can bond with oxygen (II) and maintain homeostasis.
NO BENIFICIAL FUNCTION FOUND FOR MUTATED PROTEIN
PrPSc is an agent that causes three types of disorders:
Infectious: From one part of the body to another
Genetic: Inherited
Spontaneous: Occurring with no timed execution
Alpha helices are amino acid polypeptide chains in a helical shape bonded by carboxyl and amino groups. They are also bonded secondarily by hydrogen bonds causing an increased stability.
Mechanism of Conversion:
Cystine disulfide bond breaks due to the chemical reaction with proteinase K
Sulfur free radicals interrupt the enzyme that was cutting the octarepeat allowing the region to repeat an additional 32 AA
Continued rapid mutations occur because of exposed side chains and cause the symptoms of CJD
Primary structure: 253 amino acids
Theory for Prevention of Mutation
Molecular Glue Theory: a solution that would bind to PrPSc to prevent further mutation
Contain sulfur ions – to look for free radicals
Contain copper (II) ions – to look for copper recycling mechanism
Characteristics to avoid “rejection” from Cerebral Spinal Fluid
Small quantities and concentrations because of the hypersensitivity of the brain
Secondary Structure: three alpha helices and two beta sheets
Conformation: 42% alpha helix and 30% beta sheet
Globular domain
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Primary: 253 amino acids and the extended octarepeat region
Secondary: two alpha helices and two extended beta sheets
Conformation: 3% alpha helix and 43% beta sheet
Beta sheets are amino acid polypeptide chains in a linear alignment bonded with hydrogen secondarily as well.
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Cystine Disulfide bond – stabilization of alpha and beta
Ionic hydrogen bonding takes place secondarily between alpha helices and beta sheets
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PrPC to PrPSc Mutation Changes
Disulfide bond breaks
Octarepeat Region (8 AA) – repeats
Methionine ↔ Valine (severity of the disease)
Conclusion: From researching prionic mutations it has been determined that this field is very difficult, however, proteomics is very interesting and enjoyable. I look forward to continuing this work into my undergraduate and graduate work. The multiple pathways from this point just continue to increase my interest and intent to make this my life’s work.
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PrPSc Resistance
Highly resistant to proteinase K – not invincible
Stable through: heat, proteolysis, chemical sterilization, and autoclaving
PrPC Resistance
Destroyed by proteinase K
Denatured by: heat, proteolysis, autoclaving, and chemical sterilization
The four levels of folding for protein starts at the basic sequence and then forms alpha helices and beta sheets. Those then bind together and form a globular domain and then bind with others to form a basic protein
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