Neurotransmitter Release Mechanism

A series of flashcards covering key concepts related to the mechanism of neurotransmitter release, including the roles of various proteins and calcium in synaptic vesicle fusion.

What is required for priming of vesicles to become fusion competent?

Priming requires SNARE complex assembly between syntaxin, synaptobrevin and SNAP-25.

What problem does syntaxin face in its closed configuration?

In the closed configuration, the SNARE binding domain of syntaxin is hidden.

How does UNC-13 contribute to SNARE complex assembly?

UNC-13 binds to the N-terminus of syntaxin and promotes SNARE complex assembly.

What is the significance of closed syntaxin in relation to SNARE complex formation?

Closed syntaxin is incompatible with SNARE complex formation.

What triggers fusion of synaptic vesicles?

Fusion is triggered by calcium influx through voltage-gated calcium channels in response to action potentials.

What is the effect of synaptotagmin I knockout in mice?

Synaptotagmin I knockout mice lose synchronous release of neurotransmitters.

Describe the role of calcium in the vesicle fusion process.

Calcium regulates fusion by interacting with the calcium-binding protein synaptotagmin, which triggers the fusion event.

What occurs when calcium binds to synaptotagmin's C2B domain?

C2B insertion into the target membrane causes plasma membrane curvature, lowering the energy barrier for fusion.

How does synaptotagmin affect the SNARE complexes before the Ca2+ trigger?

Synaptotagmin binds to the SNARE complex and holds it together until Ca2+ triggers the fusion process.

What occurs during the exocytosis summarized process?

Munc13 promotes SNARE complex assembly, synaptotagmin clamps primed vesicles until Ca2+ signals open Ca2+ channels, triggering vesicle fusion.

What is required for priming of vesicles to become fusion competent?

Priming requires SNARE complex assembly between syntaxin, synaptobrevin and SNAP-25.

What problem does syntaxin face in its closed configuration?

In the closed configuration, the SNARE binding domain of syntaxin is hidden.

How does UNC-13 contribute to SNARE complex assembly?

UNC-13 binds to the N-terminus of syntaxin and promotes SNARE complex assembly.

What is the significance of closed syntaxin in relation to SNARE complex formation?

Closed syntaxin is incompatible with SNARE complex formation.

What triggers fusion of synaptic vesicles?

Fusion is triggered by calcium influx through voltage-gated calcium channels in response to action potentials.

What is the effect of synaptotagmin I knockout in mice?

Synaptotagmin I knockout mice lose synchronous release of neurotransmitters.

Describe the role of calcium in the vesicle fusion process.

Calcium regulates fusion by interacting with the calcium-binding protein synaptotagmin, which triggers the fusion event.

What occurs when calcium binds to synaptotagmin's C2B domain?

C2B insertion into the target membrane causes plasma membrane curvature, lowering the energy barrier for fusion.

How does synaptotagmin affect the SNARE complexes before the $Ca^{2+}$ trigger?

Synaptotagmin binds to the SNARE complex and holds it together until $Ca^{2+}$ triggers the fusion process.

What occurs during the exocytosis summarized process?

Munc13 promotes SNARE complex assembly, synaptotagmin clamps primed vesicles until $Ca^{2+}$ signals open $Ca^{2+}$ channels, triggering vesicle fusion.

Identify the v-SNARE and t-SNARE components in synaptic vesicle fusion.

Synaptobrevin is the v-SNARE, while Syntaxin and SNAP-25 are the t-SNARE components.

How does synaptotagmin function as a $Ca^{2+}$ sensor during synaptic exocytosis?

Synaptotagmin contains C2 domains that directly bind $Ca^{2+}$, leading to a conformational change and insertion into the plasma membrane, thereby triggering fusion.

What is the relationship between UNC-13 and the closed configuration of syntaxin?

UNC-13 helps open the closed syntaxin configuration by binding to its N-terminus, making the SNARE binding domain accessible for SNARE complex assembly.

Predict the effect on neurotransmitter release if synaptotagmin could not bind $Ca^{2+}$.

Synchronous neurotransmitter release would be severely impaired or lost, similar to a synaptotagmin I knockout, as the $Ca^{2+}$ trigger for fusion would be absent.

Outline the distinct roles of Munc13 and synaptotagmin in the sequence of vesicle priming and fusion.

Munc13 facilitates SNARE complex assembly (priming), while synaptotagmin acts as