Lysosomal storage disorders Flashcards
1
Q
Who discovered LSDs?
A
Christian de Duve
2
Q
How many genes control LSDs?
A
One gene
Monogenic disease
3
Q
What type of diseases are LSDs?
A
Metabolic diseases
4
Q
Why do biological materials build up in LSDs?
A
Enzyme or membrane protein of lysosome is defective
Causes build up of proteins or substrate
5
Q
What two proteins can be defective in LSDs?
A
Lysosomal membrane proteins
Enzymes
6
Q
What is the incidence of LSDs?
A
Singularly rare
Many types of the disease
Combined frequency is very high
7
Q
How many diseases do LSDs encompass?
A
More than 60 diseases
8
Q
What type of mutation causes LSDs?
A
Many different mutations in the same or different gene causes the disease
9
Q
How do the mutations influence the gravity of the symptoms in LSDs?
A
Mutation influences
- severity of symptoms
- onset of symptoms
10
Q
Genetic analysis not enough to rule out diagnosis in patients presenting symptoms of LSD
TRUE or FALSE
A
TRUE
Not always a direct genotype-phenotype correlation
11
Q
What two factors are used to classify LSDs?
A
Substrate that builds up
Gene that is mutated
12
Q
Different gene mutations have similar phenotypic characteristics
TRUE or FALSE
A
TRUE
Same metabolic pathway is affected in the different subtypes of LSD
13
Q
What are the four main roles of the lysosomes?
A
Endocytosis/autophagy
Apoptosis
Unfolded protein response
Mitochondrial/Ca2+ balance
14
Q
What role do lysosomes play in endocytosis?
A
Internalisation of extracellular material through
- invagination
- formation of vesicles
Release of material into the intracellular lysosomal compartment
15
Q
What is autophagy?
A
Normal physiological process in the body that deals with destruction of cells in the body
16
Q
How does autophagy maintain homeostasis?
A
Protein degradation
Turnover of the destroyed cell organelles for new cell formation
17
Q
What triggers autophagy?
A
Cell starvation
18
Q
What is apoptosis?
A
Programmed cell death
19
Q
What is the role of lysosomes in apoptosis?
A
Membrane of the lysosome becomes more permeable
Release proteases into the cytosol
20
Q
Examples of proteases released from the lysosome into the cell during apoptosis
A
Cysteine
Cathepsin
21
Q
What is UPR?
A
Unfolded protein response
Unfolded proteins must be removed from the cell environment to maintain cell homeostasis
22
Q
Which two mechanisms deal with unfolded proteins in the cell environment?
A
Proteasomes
Chaperones
23
Q
How do chaperones deal with unfolded proteins?
A
Break the misfolded proteins down into their primary structure
Try to fold them into the correct shape
24
Q
What happens to the misfolded proteins if the aren’t folded into their correct shape by the molecular chaperones?
A
They are discarded in the lysosome
25
What happens to the misfolded proteins if they are folded into the correct shape by molecular chaperones?
Released systematically
26
How do mitochondria and lysosomes maintain dynamic homeostasis?
Degrade dysfuntional mitochondria
Maintain lysosomal function by acidification
Lysosomal calcium regulates mitochondrial catabolism
27
In which processes is calcium signalling useful for between mitochondria and lysosomes?
Autophagy
Membrane fusion
Apoptosis
28
What is the size of lysosomes?
1-2 micrometers
29
How many acid hydrolases and membrane proteins are found in lysosomes?
>50
30
How is the pH maintained in lysosomes?
Actively concentrate H+ by a proton pump ATPase
31
In what way is the cell adapted to withstand lysosomal damage?
pH of the cytosol is around neutral
If the lysosome cell membrane breaks down the enzymes are rendered inactive by the high pH of the cytosol
Protective
32
What processes happen if the intracellular relationships between the lysosome and surrounding organelles is disrupted?
Dysfunctional biosynthesis and catabolism of GSLs
Accumulation of substrates
Failed trafficking
Disturbed calcium signalling
Apoptosis
Necroptosis
Macrophage activation
Disturbed autophagy
Disruption of lipid raft - receptor signaling
33
Why are so many organelles affected if the lysosomes become dysfunctional?
A lot of cross-talk between lysosomes and organelles
34
Complete disruption of the GSL pathway is incompatible with life
TRUE or FALSE
TRUE
35
Why are lysosomes sensitive to enzyme mutations?
The enzymes are found in this organelle
Here is where the metabolic pathways take place
When the metabolic pathways are disrupted because of a mutation, the substrate will build up in the lysosome
36
What are glycosphingolipids?
The metabolic pathways of glycosphingoipids are affected in LSDs
The mutated proteins are involved in these metabolic pathways
37
What are the components of glycosphingolipids?
Carbohydrate + ceramide
38
Examples of specific disorders related to the disruption of the GSL pathway
Krabbe
Gaucher
Niemann-Pick disease
Fabry
Sandhoff
Batten
39
Presentation of LSD varies a lot between patients
TRUE or FALSE
TRUE
The same gene can have different mutations
Mutations can affect different organs and cell types
Affected cell population can be widespread or restricted
40
Why are LSDs so difficult to treat?
Same disease may be caused by different mutations
41
How can different genetic mutations cause the same presentations?
Mutations affect the enzymatic pathway along different points
Leads to the same substrate build-up
42
What is a broad way to classify LSDs?
Visceral
Neurological
43
Clinical features of LSDs
Organomegaly
Cardiomyopathy
Respiratory manifestations
Haematological and endocrine symptoms
Bone abnormalities
44
Main characteristic of neuropathologies related to LSDs
Leads to premature death
45
What are the symptoms of neuropathology in LSD
Neurocognitive impairment
Movement disorders
Seizures
Deafness
Parkinson's
46
Pathogenesis of LSDs - Krabbe disease
Metabolites from GAGs build up
These are recognised by TLRs
Causes secretion of cytokines
Apoptosis of cells
47
What substrate accumulated in Gaucher disease?
Glucocerebroside
48
What causes the substrate accumulation in Gaucher disease?
CBA gene coding for b-glucocerebroside is defective
49
Which cells are particularly affected in Gaucher disease?
Macrophages
Gaucher cells
50
What is the main symptom of Gaucher disease?
Organ enlargement
As the enlarged cells enter the organs
51
What is the condition where the spleen and liver become enlarged called?
Hepatosplenomegaly
52
How many types of Gaucher disease exist?
3 types
53
Describe type 1 Gaucher disease
Visceral presentation of pathology
Most common type
The b-glucocerebosidase enzyme is less efficient but still functional
54
Describe type 2 Gaucher disease
Acute neuropathology
Death < 2 years of age
Enzyme is affected so the active site is disrupted and completely dysfunctional
55
Describe type 3 Gaucher disease
Chronic neuropathy
Slow progression
56
What accumulates in cells during Niemann-Pick disease
CHolesterol
Sphingolipids
57
What two types of Niemann-Pick disease exist
Type A and B
Type C
58
What distinguishes the different types of Niemann-Pick disease
Genes that are mutated
59
What gene is mutated in types A and B Niemann-Pick disease?
SMPD1
60
What genes are mutated in type C Niemann-Pick disease?
NPC1 and NPC2
61
What does SMPD1 code for?
Enzyme
Sphingomyelinase
62
What do NPC1 and NPC2 code for?
Membrane proteins
63
Where are the manifestations of Niemann-Pick disease observed in the body?
Type A and B - viscera
Type C - viscera and nervous system
64
Neurodegenerative symptoms in type C Niemann-Pick disease
Delay in motor milestones
Ataxia
Psychiatric problems
65
Which gene mutations lead to Batten disease?
Neuronal ceroid lipofuscinoses
400 mutations in 13 different CLN genes
66
In Batten disease, depending on the ----- affected, the ---- of the disease is different
Gene
Onset
67
At which developmental stages can Batten disease be observed?
Infantile
Late infantile
Juvenile
Adult
68
Symptoms of Batten disease
Visual impairment
Seizures
Neurological symptoms
Premature death
Maculopathy and retina atrophy
69
What analysis is needed to diagnose LSD?
Biochemical and genetic analysis
70
What are sources of complication when it comes to diagnosing LSDs?
Rare disease - no routine prenatal screening
Often misdiagnosed due to the heterogeneity in symptoms
Lack of biomarkers
71
Examples of newborn screening to diagnose LSD
Enzymatic activity in blood spots
Detection of urinary oligosaccharides or glycosaminoglycans
Indirect biomarkers
Skin biopsy
72
---- diagnosis is essential for diseases with ------
Early
Neurological involvement
73
What are the different approaches of how to treat LSDs
Treat
- the symptoms
- cell dysfunction and cell death
- substrate storage
- enzyme or protein defect
- gene defect
74
LSD therapies are normally exclusive
TRUE or FALSE
FALSE
LSD therapies are normally not exclusive
75
What is the primary care for patients with neuropathologies?
Suppotive care for individuals and their families
76
What types of LSDs are particularly hard to treat?
LSDs that involve
- dysfunctional membrane proteins
- insoluble enzymes
- the BBB
77
What are the main therapies for LSDs?
```
Transplantation
Substrate reduction therapy
Enzyme replacement therapy
Molecular chaperones
Gene therapy
```
78
Procedure of transplantation
1. Multipotent stem cells are obtained from the BM, peripheral blood and umbilical cord
2. Bone marrow from suitable healthy donor is the therapeutic agent
3. Healthy haematopoietic cells spread throughout organs
4. Secrete missing enzyme
79
Why does haematopoietic stem cell therapy help sufferers with neurological presentation?
Microglial cells of haematopoietic origin can cross the blood-brain barrier and secrete the therapeutic enzyme in the brain
80
What is the main goal of stem cell therapy?
Slow or arrest neurodegeneration
Replace the defective enzyme before significant CNS injury
81
What are the disadvantages of stem cell therapy?
Cannot help with diseases where the condition derives from faulty intermembrane proteins
Minimal improvement is seen
No effect on CNS
82
What is the aim of substrate reduction therapy?
Reduce the synthesis of the accumulating substrate
83
Two examples of drugs involved in substrate reduction therapy
Miglustat
Eliglustat
84
How does Miglustat reduce the substrate concentration?
Competitively inhibits the upstream enzyme
Blocks the biosynthesis of the overproduced substrate
85
Diseases that Miglustat targets
Gaucher
Fabry
86
Advantage of Miglustat
Crosses BBB
87
Disadvantages of Miglustat
Causes GI problems
Disrupts metabolic pathway higher up than the overproduced substrate
88
Another example of a substrate reducing therapy
Eliglustat
89
Disadvantage of Eliglustat
Cannot cross the BBB
Drug transporter causes the compound to be pumped out of the CSF
90
What has been the most successful treatment of LSDs to date?
Enzyme replacement therapy
91
What is enzyme replacement therapy based on?
Replacement of the defective enzyme by systemically administering the recombinant protein
92
It is proven that partial levels of enzymatic activity might be sufficient to help stabilise symptoms of LSD
TRUE or FALSE
TRUE
93
How are recombinant enzymes produced?
Using recombinant DNA technology
Tagged with a moiety that allows the enzyme to enter the cells and traffic to the lysosomes
Produced in an industrial scale
94
What are the advantages of using recombinant enzymes as therapy for LSD?
Safe and well tolerated
Rarely causes an immune reaction
Suitable for cross-correction
95
What is cross-correction?
Process by which a recombinant protein can be replicated in the cell and transported to neighbouring cells
96
What moiety are the recombinant proteins bound to?
Mannone-6-phosphate
97
What cellular process do pharmacological chaperones take advantage of?
Molecular chaperones
98
What do molecular chaperones do?
Bind to nascent polypeptides and promote correct folding of them
Traffic mutant proteins that are not able to be folded correctly to be lysed
99
What condition must proteins express in order to be suitable to be corrected by chaperones?
Must possess residual enzymatic activity - the mutation cannot affect the active site
100
What are the aims of using molecular chaperones as therapy for LSDs?
More enzymatic activity is retained in the lysosome
Small change in enzymatic activity can affect the quality of life
101
What are the names of two molecular chaperones used as therapy for LSDs?
Migalastat
Arimoclol
102
Which condition does Migalastat treat?
Fabry disease
103
How does Migalastat treat Fabry?
Binds to the active site of misfolded a-galactosidase A
104
Which condition does Arimoclomol treat?
NPC
105
How does Arimoclol treat NPCs?
Co-inducer of the heat-shock response
Activates the natural cellular repair pathways
106
What is gene therapy?
Process by which a mutated gene that causes disease is replaced with a therapeutic copy using a viral vectors
107
What are two ways to perform gene therapy?
In vivo
Ex vivo
108
What does in vivo gene therapy involve?
Inject the vectors directly into the body where the faulty cell's DNA is affected
109
What does ex vivo gene therapy involve?
Take out cells from the body
Inject the vector into the cell
Place them in the incubator
Add the cells to the body
110
What types of vectors can be used in gene therapy?
Non-viral
Viral
111
Examples of non-viral vectors
Naked DNA
Nanoparticles
Biovesicles
112
Examples of viral vectors
Lentivirus
Adenovirus
Adeno-associated virus
113
Advantages of gene therapy
Targets the CNS
Cross-correction
Liver is a good target
Long-term therapy
114
What is cross-correction?
Translation of beneficial proteins from genetically altered cells enter cells surrounding them
115
Why is the liver a good target for gene therapy?
Vectors have a great effect on hepatocytes
Genetically modified cells can produce the advantageous protein
Travel to neighbouring organs in the circulation
116
What are the disadvantages of gene therapy?
Gene delivery needs to be targeted to a specific cell population
Difficult to determine the concentration of protein needed and longetivity of effects
Needs to avoid the immune response
Cost
117
Why does the advantageous gene need to be targeted to specific cell populations?
Protein produced may be beneficial in some organs and dangerous in other
118
How is the long-term effectiveness of gene therapy sometimes hazardous?
If too much protein is made, past the natural concentration, pathological effects may develop
119
Why are AAVs used often as gene delivery vectors?
Efficient at delivering gene therapy
High titer
Causes mild immune response
Interacts with a broad number of cells
Very safe
