General mechanisms in neurodegeneration Flashcards
what defines a neurodegenerative disorder
damage on different brain regions where occlusions are localised.
What do occlusions consists out of?
aggregates.
what are aggregates
misfolded, clustered (hydrophobic beta sheets) proteins
what can aggregates lead to?
- loss of function phenotype
2. gain of toxic function
how are aggregates controlled
protein quality control
where does protein synthesis take place
proteins are synthesised in the cytosol and the ER
cytosol: proteins that are packed to be transported
ER: proteins that are soluble
what proteins prevent the binding of misfolding proteins?
chaperones (heat-shock proteins)
how do HSP/chaperones prevent misfolded protein binding?
chaperones facilitate protein folding and refolding by keeping proteins in “a folding-competent state”
which chaperone is very important in ND’s
HSP70, HSP90, HSP60 (ATP dependent)
hsp small (ATP independent)
Define the HSP70 cycle
this cycle is ATP dependent and a co-chaperone
groove where misfolded protein fits –> lid closes –> ATP hydrolysed –> misfolded protein is unfolded –> lid open again –> unfolded protein had another change to fold into the correct form.
what happens if chaperones fail to refold the protein?
the misfolded protein will receive an ubiquitin tag (ubiquitin chain)
what is the function of an ubiquitin tag
This tag is added to the misfolded protein to be identifiable for degradation.
which molecule recognised the ubiquitin tag for degradation
it is recognised by the proteasome (enzyme), inside this proteasome chamber are degradative enzymes which break the amino acid backbone. The amino acids are released after degradation.
name the catalytic chamber of the proteasome
20S core particle
What is the consequence of proteasome inhibition
proteasome inhibition induces the accumulation of polyUb proteins. (ubiquitinated proteins)
define autophagy
Autophagy = The body’s way of cleaning out damaged cells, in order to regenerate newer, healthier cells
it is initiated by wrapping a membrane structure around the material that has to be degraded. it is also a manner to degrade dysfunctional mitochondria.
needed for quality control of proteins.
what are the proteolytic pathways
- proteasome = degrades monomeric proteins
2. autophagy = degrades larger structures (organelles, aggregates)
name the neurodegenerative diseases aetiology
- sporadic (majority)
- acquired (prion disease)
- genetic
define inclusion body
Inclusion bodies are dense, spherical, aggregated proteins, mostly formed in the cytoplasm of prokaryotes due to overexpression of heterologous proteins
how to mutations in aggregating proteins lead to neurodegenerative disorders
aggregates can become toxic
which neurodegenerative disease is genetic only?
Huntington’s disease
son gets 50/50 chance.
which mutation in the Huntington disease leads to toxic aggregate formation
the repeat sequence encodes for more than 35 glutamine residues to be bound together.
affects the basal ganglia and the chorea (movement)
fibril formation and ND’s are connected but not quantitively, the inclusion bodies are directly connected
ok?
explain the aggregation cascade
small oligomeric aggregates –> fibril aggregates –> fibrils deposit in inclusion bodies