Flashcards
amyloid diseases
Cards in this deck (39)
- 1what is the consequence of protein misfoldingWhen proteins are folded incorrectly there is the chance this can cause pathologies
- There are many consequences of protein misfolding - 2give examples of inheritable proteopathiescystic fibrosis
sickle cell anaemia
familial amyloidosis
cancer - 3give examples of non-inheritable proteopathiesalzhiemers disease
survy
cancer - 4what is the consequence of the protein misfiling in the case of C.F.lack of function of chloride ion channel that results the inability to secrete chloride ions on mucosal surfaces
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misfiled state of proteins can be dangerous (toxic)--> Amyloids called prions - 5describe what is the main cause of C.F at a genetic level- 1480 amino acids and 1500 known mutations that are known to be assocaited with CF however 70% of cases are cause by a point mutation of the ΔF508 (deletion)
- This sits in the interface of the transmembrane domain 2 and the nucleotide binding domain 1; reason for dramatic consequence is not due to the change in folding but due to the protein that is modified in the E.R. because of the lack of this amino acid cannot fold into correct structure quickly enough and remains bound to a heat shock protein in the E.R.
- - 6why does the CFTR protein become degraded in cellsProlonged interaction of the chaperone and the protein triggers degradation response of the cell; any protein that does not form quick enough will be destroyed by the cell
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6This is the cause of CF- not that the protein cannot carry out the function but because there isnt enough present- because it is degraded by the E.R. - 7what is amyloidmisfolded state that can form from any protein (in theory)
- Misfolding happens or is likely in conditions that result in the unfolding of proteins e.g. stress situations such as heat shock - 8what causes the formation of amyloid- Critical part is the partial denaturation; once folded it cannot easily form amyloids but upon the disruption of the structure the amyloid state can be formed
- May be due to the exposure of hydrophobic residues that are usually found in the protein core- causing these to interact with other hydrophobic residues
- High concentration of these misfolded states increases the likelihood of the formation of aggregation
- Degradation of proteins occurs within the body regularly, with age these processes are known to slow and not be as efficient - 9name the main factor that leads to the toxicity of mis-folded protein statesconcentration dependent
- 10why are high concentrations of amyloid dangerous within the cell- High concentration can persist within the cell for longer and can refold into forms that are not well defined
- Once the 'seeds' of amyloid are formed they have the ability to grow, growing to filaments which are stable and cannot be degraded effectively--> this is where problems arise - 11summarise the formation of amyloidstructural changes from the protein native state can cause aggregation, these can persist within the cells if degradation mechanisms are not fully functional
- 12how can amyloid diseases be defined within the bodydeposition of amyloid in extracellular protein fibrils
- Can be identified within tissues through staining with Congo red; high affinity to the amyloid structures - 13describe the structure of amyloid aggregates within the body and how this may be identifiedcross structure B-diffractions pattern when examined with X-ray fibre diffraction that can allow for its identification from other aggregated structures within the body
- 14what are levy bodies- In previous years it is clear that amyloid is not only extracellular deposits- e.g. Parkinson's --> is one of the most common neurodegenerative diseases. The deposits here are intracellular. These are called lewy bodies
- 15what differs about Parkinson's compared to other amyloid diseasesmost amyloid diseases result in extracellular deposits
-->Parkinson's the deposits are intracellular - 16what are the two different forms of amyloid diseases (named on what tissues they can be found in)localised
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systemic - 17describe a localised amyloid diseasealzhiemers- the amyloid is positioned in the brain and nowhere else
- There is a couple of proteins in Alzheimer's that cause the formation of the amyloids the most common of these is the breakdown product of APP (amyloid precursor protein)
- The breakdown product are peptides that vary in length from 40-43 amino acids
Peptide that forms amyloid known as the amyloid beta peptide - 18describe systemic amyloidosisheritable
- Position of amyloid anywhere within the body - Associated with internal organs such as the spleen, liver and kidneys
- Not strictly defined where the deposits are found - 19formation of systemic amyloidosisBeta-2-microglobulin -> forms amyloids in patients that undergo haemodialysis frequently
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- Artificially introduced disease
- Most likely caused by the mechanical stress that blood undergoes/ experiencing during haemodialysis and the production of the amyloid aggregates
Served as one of the model proteins for the understanding of the amyloid formation - 20what was seen to clear up a case of amyloidosis in a patient that was suffering from cancerradio labelled antibodies were used for the identification of of the amyloid
after a period of chemo there was a great reduction in the volume of the protein - 21describe localised amyloidsis with an examplealzheimers
formed by the amyloid beat protein
can be show by positron emission tomography (PET)
injection of the patient with radio labelled short lived isotopes that emit positrons - 22describe how PET scanning can be used in the identification of a localised amyloid diseasealzheimers
- injections of labelled and short lived isotopes that emit positions
- Carbon 11 (PIB) used to detect the amyloid plaques and Fluorine 18 (FDG) are used to detect metabolic defects
- Short half life- has to be prepared in close proximity to the patient
- PIB has a high affinity for amyloid
- Fluorine labelled glucose- where it can be seen is where it has not been turned over- metabolism is down
- Severe metabolic defect in the Alzheimer's patient - co-localised with the amyloid plaques - 23what is biofringence - and what can this tell us about the structure of amyloid- Birefringence is an optical property of crystalline substances and is only observed in crystals
- This indicates that this dye is arrange in a regular crystalline structure and that the basic structure of amyloid is a well ordered assembly of protein - 24what proteins within the body are amyloidogenicAlmost any protein can be turned into amyloid
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- Diverse and different (alpha helical and beta- some do not form full structures)
- Myoglobin is a well folded protein, however, under certain conditions it is capable of forming amyloid - 25how is the formation of amyloid inducedAmyloid formation is always induced by either the presence of natively unfolded protein structures or partially unfolding of well folded structures
- Denaturation to some extent is required for the formation of amyloid - 26descrive a limitation of the anfinsens dogmaProtein aggregates are more stable than native proteins (and kinetically trapped)
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This is something that Anfinsen either didn’t consider/didn’t know but issues arise because these protein aggregates are much more stable than the aggregates - 27what causes a protein to move from a natively folded protein to a misfiling landscape--> concentration
Must have conditions that favour the unfolding while allowing the concentration of the amyloid to build-up - 28what structure has been identified in amyloid-->dry steric zipper
high resolution structures of amyloid have been reported
- concentration
Must have conditions that favour the unfolding while allowing the concentration of the amyloid to build-up - 29describe the structure of a steric zipperyellow- water purple and white are two beta stands packed together to form steric zipper
side chains come together like the teeth of a zipper - 30what was shown about the steric zipper structure in different amyloid- Found that while the dry self complementing zipper was always the key feature of the amyloids the topology differed -->different ways that the strands can be arrange (parallel, antiparalled, back to back, head to head)
- 31how many different classes of steric zipper have been shownIdentified 7 different classes of how beta sheets can come together in self complementing dry steric zipper
- 32what is the function of the steric zipper- how do we know this?Modern day structural biology techniques allow us to look at full, intact amyloid; even that isolated from patients can be investigated by CryoEM
- Structure of the full amyloid beta peptide from Alzheimer's disease showing the self complementing dry steric zipper has been determined - this is a key feature of the amyloid
Zippers seen to hold together fibrils - 33what protein is the cause of pathogenic amyloid formation in parkinsons diseasehuman alpha-synuclein
- 34describe why we can identify that parkinsons disease is an amyloid disease despite it being intracellularLewy bodies are intracellular amyloid deposits in Parkinson's disease
Different forms in different regions of the brain
Structure that it adopts is the same as those adopted by other amyloid conditions, confirming that despite intracellular location this is a amyloid disease - 35what structural biology tool can be used fro the solving amyloid structuresCryoEM
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- Solve these for individual patients with the same disease shows that there is individual differences between patients
- Doesn’t always look the same- the zipper is always a key feature - 36what are invisible crystals- Resolution of structure obtained through micron- electron diffraction on crystals that are so small that they are not suitable for x ray crystallography (due to their small size) resolution that can be obtained is high (1.4A)
- 37what can micron electron diffraction be used forAble to tell that the side chains in the zipper are well defined - revealing the architecture of the amyloid in great detail
- 38how do the mis-folded proteins gain toxicity and cause cell damage- Vesicle that should be round, is distorted at the point of contact with the amyloid
- Clear that the amyloid can interact with the membrane resulting in distortion of the membrane architecture
Doesn’t associate with the membrane everywhere- just the tips. This is an important observation as there is much discussion as to which form of amyloid is toxic
- 39what does a cryoEM tomography tell you about the movement/ formation of amyloid within Alzheimers- Seems that this might be a process of export
Long mature fibrils that are penetrating the membrane
Amyloid typically considered to be extracellular with the main exception of this being Parkinson's disease --> current research is showing that amyloid play a far more important role intracellularly that previously considered - may well be that they are first formed inside and then exported out of the cell
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- Protein structure and function Flashcards on amyloid diseases , created by Samantha bruce on 06/12/2019.
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- Samantha bruce
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