Questions and Answers
What are SNAREs?
Attachment protein receptors that drive the fusion of two membranes - mediate exocytosis.
What are v-SNAREs and t-SNAREs?
v-SNAREs are part of the vesicle membrane, and t-SNAREs are part of the target.
Give an example of a v-SNARE and t-SNARE.
v-SNARE = synaptobrevin/VAMP; t-SNARE = syntaxin, SNAP25.
What are the functions of t-SNAREs?
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What is the process of vesicle fusion mediated by SNARE complexes?
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What is the role of SNAREs in autophagy?
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How do SNARE complexes mediate nervous system excitation?
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How is the SNARE complex disassembled for recycling?
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What protein inhibits NSF and SNAP proteins, affecting SNARE complex recycling?
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Why are SNARE molecules required to drive membrane fusion?
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What are mutations in SNAP complex associated proteins associated with?
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How can the function of SNAREs be targeted for treatment of neurological conditions?
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How is botulinum toxin paralysis naturally reversed?
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Study Notes
SNARE Proteins Overview
- SNAREs are attachment protein receptors that drive membrane fusion, essential for exocytosis.
- All SNARE proteins share a conserved SNARE motif/domain.
Types of SNAREs
- v-SNAREs are located on vesicle membranes.
- t-SNAREs are situated on target membranes.
Examples of SNAREs
- v-SNARE example: Synaptobrevin (VAMP), localized to synaptic vesicles.
- t-SNARE examples: Syntaxin and SNAP-25, primarily found on neuronal plasma membranes.
- Synaptogamin functions as a calcium sensor.
Functions of t-SNAREs
- Typically associated with nerve terminal membranes.
- SNAP-25 enhances membrane fusion specificity by forming a tight complex that facilitates fusion of synaptic vesicles with plasma membranes.
Vesicle Fusion Process
- Vesicle trafficking involves docking at the target membrane.
- Activation of SNARE proteins occurs post-docking to fuse vesicle and target membranes.
Role of SNAREs in Autophagy
- In macroautophagy, SNAREs are involved in phagophore formation and fusion with lysosomes.
- Autophagosomes degrade cellular components through lysosomal fusion, mediated by SNAREs.
SNARE Complex in Neuronal Activity
- Synaptobrevin is present on vesicles containing neurotransmitters.
- The target brain membrane contains t-SNAREs, specifically syntaxins 1, 2, 3.
- Fusion creates a trans-SNARE complex, leading to neurotransmitter release.
Disassembly of SNARE Complex
- NSF and SNAP proteins disassemble the SNARE complex for recycling.
- ATP hydrolysis provides the energy necessary for disassembly.
Inhibition of SNARE Complex Recycling
- NEN protein inhibits NSF, preventing SNARE complex disassembly and affecting recycling efficiency.
Importance of SNAREs in Membrane Fusion
- SNAREs facilitate rapid vesicle release by being pre-primed in a partly paired state, avoiding extensive rearrangements during fusion.
Mutations in SNARE-Associated Proteins
- VAMP1 mutations are linked to Alzheimer’s disease due to impaired Aβ-containing vesicle fusion.
- Syntaxin11 mutations cause FHL4, affecting T-cell cytotoxic granule secretion and leading to immunodeficiency.
Therapeutic Targeting of SNARE Functions
- Botulinum toxins target SNAREs to inhibit acetylcholine release at motor neurons, resulting in muscle paralysis.
Reversal of Botulinum Toxin Paralysis
- Botulinum toxin leads to SNARE protein cleavage, but natural turnover of SNARE complexes can restore function.
- Botulinum toxin is taken up into vesicles, endocytosed, and cleaves SNARE proteins like SNAP-25, disrupting neurotransmission.
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Description
Explore the fascinating world of SNARE proteins with these flashcards. Learn about the roles of v-SNAREs and t-SNAREs in membrane fusion and exocytosis. Test your knowledge with examples and definitions to deepen your understanding of cellular processes.