Flashcards in L3 - Lysosomal Storage Disease Deck (35):
Features of LSD?
- Rare, 1/8000 live births
- Death in childhood
- Store material in lysosome due to defects in substrate degradation
Features of the lysosome
- 70 hydrolytic enzymes
- low pH (4)
- Enzymes trafficked to it via M6P receptor pathway
- Material trafficked by endocytosis or autophagy
What problem does the neuron create for endocytosis?
Trafficking problem in that lysosomes not present at synapse
What is M6P?
Mannose-6-phosphate group added to hydrolases destined for lysosome
What are the steps in the M6P pathway?
- Added to hydrolases through Golgi
- Recognised by M6PRs and deliver to late endosome
- Low pH causes dissociation
What are the general cellular phenotypes of LSD?
Accumulation of ageing pigment
Defects in autophagy
Appearance of meganeurites
What are the features of mucopolysaccharides?
Component of cell membranes
Mutation causes defective metabolism and accumulation of GAGs
What does MPS stand for and what is it?
Accumulation of secondary storage substrates
Features of Sanfilippo Syndrome (MPS III)
Cannot break down Heparan sulphate
Most common MPS
What are the symptoms of Sanfilippo Syndrome?
How can you screen for Sanfilippo Syndrome?
GAGs in urine
What is mucolipidosis-II also known as?
I-Cell disease or Psuedo-Hurler
What are the symptoms and occurrence of I-Cell disease?
Developmental delay, death early
1/640000 live births
What is the genetic defect of I-Cell disease?
What are the internal symptoms of I-Cell disease?
I = Inclusion so stored material is mucolipds, MPS and schingolipids
What are the internal symptoms of Mucolipidosis-IV
Stored material = mucolipids, MPS, sphingolipids
What is the occurance and symptoms of Mucolipidosis-IV
Occurrence - Jewish 1/90
Symptoms - physchomotor retardation, corneal opacity, retinal degeration, iron definiency, improper stomach pH
What is the genetic defect of Mucolipidosis-IV?
Mucolipin1 and a TRP channel involved in iron efflux from lysosomes
What is important about spingolipids?
A major component of neural tissue and binds cholesterol
What is the usual path of sphingolipids in a cell?
Patches on membrane endocytosed then recycled by TGN
Small amount leak out and are degraded
What is the path of sphingolipids in LSD?
Schingolipids and cholesterol routed mainly to lysosome, swamping them
What are the Symptoms and occurrence of Tay-Sachs disease?
Early death, neurological deterioration (ataxia, atrophy, spasticity)
1/27 in Ashkenazim Jews, Cajuns
What is the genetic defect causing Tay-Sachs disease?
Hexosaminidase A (HEXA)
What are the internal symptoms of Tay-Sachs disease?
GM2 gangliosides, globosides and glycolipid build up
What are the symptoms and occurrence of Niemann-Pick disease?
Enlarged liver, and lymph nodes, darkening of skin, neurologic impairment, cherry red spot
Occurrence 1/1000 Ashkenazim Jews
What is the genetic defect for Niemann-Pick disease?
Mutant for sphingomyelinase
What are the internal symptoms of Niemann-Pick disease?
Build up of sphingomyelin, cholesterol and sphingolipids
Causes endosomal traffic jam
What are all the features of Batten disease?
Defect - CLN genes 1-8
Occurrence - 1/8000
Symptoms - visual defects, seizures, loss of sight speech and motor skills, dementia
Storage material - lipofuscin
What are some possible treatments of LSD?
Neuronal stem cells
What is spinster?
A gene identified for synaptic growth in drosophila (synapses overgrown in mutant)
12 transmembrane transporter
Where does spinster localise?
To a low pH late-endosomal compartment with lysomal associated membrane protein (LAMP)
What does spinster cause intracellularly?
Expanded endosome and multi-lamellar inclusions
Whats a good way of detecting sphingolipids?
Filipin is a fluorescent antibiotic that binds cholesterol
What does spinster do and how can it be rescued?
Bears an oxidative stress burden.
Reducing oxidative stress rescues synaptic overgrowth