SNARE Proteins Flashcards

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?

They are associated with nerve terminal membranes and execute fusion by forming a complex that brings membranes together. Signup and view all the answers

What is the process of vesicle fusion mediated by SNARE complexes?

The vesicle docks with the target membrane, and SNARE proteins mediate the fusion of membranes. Signup and view all the answers

What is the role of SNAREs in autophagy?

SNAREs mediate the fusion of autophagosomes with lysosomes to degrade cellular components. Signup and view all the answers

How do SNARE complexes mediate nervous system excitation?

SNARE complexes form during membrane fusion, releasing neurotransmitters from vesicles. Signup and view all the answers

How is the SNARE complex disassembled for recycling?

NSF and SNAP proteins disassemble the SNARE complex using ATP energy. Signup and view all the answers

What protein inhibits NSF and SNAP proteins, affecting SNARE complex recycling?

NEN protein inhibits NSF. Signup and view all the answers

Why are SNARE molecules required to drive membrane fusion?

They facilitate rapid release of molecules from vesicles without extensive rearrangements. Signup and view all the answers

What are mutations in SNAP complex associated proteins associated with?

VAMP1 mutations are associated with Alzheimer's disease; Syntaxin11 mutations affect T-cell functions and cause immunodeficiency. Signup and view all the answers

How can the function of SNAREs be targeted for treatment of neurological conditions?

Botulinum toxins inhibit ACh release from cholinergic neurons, leading to muscle paralysis. Signup and view all the answers

How is botulinum toxin paralysis naturally reversed?

Through the natural turnover of SNARE protein complexes. Signup and view all the answers

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.

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.