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L2 Molecular Cell Biology > SNAREs > Flashcards

SNAREs Flashcards

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1
Q

What are examples of membrane fusion? (5)

A
  • Synaptic vesicle fusion
  • Secretory granule fusion (endocrine and exocrine pancreas)
  • Secretion of serum proteins (antibodies, albumin)
  • Mucus secretion
  • Intracellular transport of proteins between organelles
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2
Q

What are the components of the neuronal SNARE complex? (3)

A
  • VAMP (V-SNARE)
  • Syntaxin (T-SNARE)
  • SNAP25
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3
Q

What is the structure of the SNARE complex? (6)

A
  • VAMP/V-SNARE is on the vesicle
  • SNAP25 and syntaxin/T-SNARE are on the target membrane
  • SNAP25 has 2 coiled-coil (SNARE) domains, VAMP and syntaxin have 1 (3Q:1R)
  • Proteins zipper up via hydrophobic domains
  • Syntaxin folds back on itself to form a regulatory domain
  • Salt-bridge forms at the zero layer of the SNARE complex
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4
Q

What are the 2 types of SNAREs?

A
  • R SNAREs
  • Q SNAREs
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5
Q

What are R SNAREs? (2)

A
  • Have an arginine in the position of the zero layer of the SNARE complex
  • i.e. VAMP/V-SNAREs
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6
Q

What are Q SNAREs? (2)

A
  • Have a glutamine in the position of the zero layer of the SNARE complex
  • i.e. syntaxin/T-SNAREs and SNAP25
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7
Q

What is the SNARE ratio in the complex?

A

3Q:1R is conserved in all complexes

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8
Q

Which components provide the specificity of membrane fusion? (2)

A
  • SNAREs mostly interact with SNAREs from the appropriate membranes but show some promiscuity
  • Additional machinery e.g. rabs, coat proteins, tethers contribute to specificity
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9
Q

What is NSF? (3)

A
  • Unwinds the SNAREs after fusion for recycling
  • Requires ATP hydrolysis
  • Involved in the 20S complex
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10
Q

What are the features of SNARE proteins? (2)

A
  • Small C-terminally anchored proteins
  • All contain at least 1 coiled-coil domain
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11
Q

How does fusion occur? (4)

A
  • SNARE complex zippers together to bring the membranes close enough to overcome the repulsion of the lipid bilayers
  • Destabilisation of the membranes for fusion
  • SNAREs end up on the same membrane
  • NSF unzips the SNAREs for recycling
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12
Q

What is the evidence for NSF in drosophila? (3)

A
  • Identified temperature sensitive drosophila mutants
  • Comatose mutant was paralysed at the restrictive temp, had mutant NSF
  • Comatose flies have an accumulation of docked vesicles because the SNAREs can’t be recycled
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13
Q

What is the phenotype of a VAMP2 knockout mouse? (2)

A
  • Die at birth
  • Loss of synaptic transmission
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14
Q

What is the phenotype of a syntaxin1A knockout mouse? (2)

A
  • No gross abnormalities
  • Reduced synaptic transmission
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15
Q

What is the phenotype of a syntaxin1B knockout mouse? (2)

A
  • Die after birth
  • Reduced synaptic transmission
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16
Q

What is the phenotype of a SNAP25 knockout mouse? (2)

A
  • Die at birth
  • Loss of synaptic transmission
17
Q

What is caused by heterozygous mutations in VAMP2? (2)

A
  • Neurodevelopment disorder with hypotonia (floppy baby syndrome)
  • Mutations in the coiled-coil domains
18
Q

What is a liposome fusion assay? (2)

A
  • Membrane fusion shown by an increase in fluorescence
  • Can introduce mutations and see how it affects membrane fusion
19
Q

What is caused by heterozygous mutations in syntaxin 11? (3)

A
  • Familial hemophagocytic lymphohistiocytosis (FHL4)
  • Syntaxin 11 is involved in the immune system
  • Killer T-cells are unable to secrete lytic granules to kill infections
20
Q

Why are severe diseases useful to research?

A

Gives you insight into how fundamental proteins work

21
Q

What diseases are caused by neurotoxins? (2)

A
  • Tetanus
  • Botulism
22
Q

What is the structure of clostridial neurotoxins? (3)

A
  • Targeting domain (binds to neuron)
  • Translocation domain (get into the neuron)
  • Protease domain (cleaves SNAREs)
23
Q

What is the target of BoNTA?

A

SNAP25

24
Q

What are the symptoms of tetanus? (3)

A
  • Go rigid
  • Intense muscle spasms
  • Stops the action of SNAREs in inhibitory neurons
25
Q

What are the symptoms of botulism? (3)

A
  • Go floppy (paralysis)
  • Hypotonia (floppy baby syndrome)
  • Stops the action of SNAREs in the neuromuscular junction
26
Q

What are the clinical uses of botulinum neurotoxins? (3)

A
  • Cosmetic uses
  • Strabismus, blepharospasm, overactive bladder, muscle spasticity, potentially chronic pain etc.
  • Most products based around Botulinum A and SNAP25

L2 Molecular Cell Biology (13 decks)

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