Active zone

Active Zone The Active Zone is a specialized region within the presynaptic terminal where neurotransmitter vesicles dock and fuse in response to stimulation, leading to neurotransmitter release into the synaptic cleft. This process is fundamental to neurotransmission, the primary method of communication between neurons.

Structure

The active zone is characterized by a high density of proteins that are involved in the docking and fusion of neurotransmitter vesicles. These proteins include SNAREs, Munc13, RIMs, and Liprin-alpha. The active zone is also associated with the cytoskeleton, which helps to position the vesicles for release.

Function

• The primary function of the active zone is to facilitate the release of neurotransmitters from the presynaptic neuron. This is achieved through a process known as exocytosis, in which the vesicles fuse with the presynaptic membrane and release their contents into the synaptic cleft. The neurotransmitters then bind to receptors on the postsynaptic neuron, leading to a change in its electrical activity.

• The active zone also plays a role in the recycling of vesicles. After exocytosis, the vesicle membrane is retrieved by endocytosis and refilled with neurotransmitter for future release.

Clinical significance

Alterations in the structure or function of the active zone can lead to neurological disorders. For example, mutations in the genes encoding active zone proteins have been linked to autism, schizophrenia, and intellectual disability. Furthermore, the active zone is a target for certain neurotoxins, such as botulinum toxin, which inhibits neurotransmitter release by cleaving SNARE proteins.

See also

• Synapse
• Neurotransmission
• Exocytosis
• Endocytosis

References

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