Untitled Flashcards Set

Exocytosis

• SNARE proteins: These are key for vesicle docking and fusion. Synaptobrevin (on the vesicle), SNAP-25, and syntaxin (on the plasma membrane) form the SNARE complex, which drives membrane fusion.

• Synaptotagmin: Acts as a calcium sensor, triggering vesicle fusion upon calcium influx.

• Complexin: Stabilizes the SNARE complex in preparation for calcium-triggered release.

Endocytosis

• Clathrin: Forms a cage around vesicles to mediate their retrieval from the plasma membrane.

• Adaptor protein complex 2 (AP2): Binds to synaptotagmin on the vesicle and recruits clathrin.

• Dynamin: A GTPase that wraps around the vesicle neck and facilitates its fission from the plasma membrane.

• Actin cytoskeleton: Provides structural support and helps move vesicles within the cell.

Neurotransmitter Loading

• Vesicular transporters: Specialized proteins that load neurotransmitters into vesicles using a proton gradient. For example:

  • VGLUT for glutamate.

  • VMAT for monoamines like dopamine and serotonin.

  • VIAAT for GABA and glycine.

• V-ATPase: Generates the proton gradient necessary for vesicular neurotransmitter uptake.

Neurotransmitter Clearing

• Astrocytes: Play a significant role by taking up neurotransmitters like glutamate and GABA from the synaptic cleft.

• Neurotransmitter transporters:

  • EAAT (excitatory amino acid transporters) for glutamate.

  • GAT (GABA transporters) for GABA.

• Enzymes: Degrade neurotransmitters in the synaptic cleft. For example:

  • Acetylcholinesterase (AChE) for acetylcholine breakdown.

  • Monoamine oxidase (MAO) for monoamine neurotransmitter breakdown.

Neurotransmitter Loading

• vAChT: Transports ACh into vesicles using a proton gradient established by V-ATPase.

Neurotransmitter Clearing

• Acetylcholinesterase (AChE): Breaks down acetylcholine in the synaptic cleft into acetate and choline.

• Na+/choline symporter: Reuptakes choline into the presynaptic terminal for resynthesis of ACh by choline acetyltransferase (ChAT).