glutamate secretion

Definition

Target type: biologicalprocess

The controlled release of glutamate by a cell. The glutamate is the most abundant excitatory neurotransmitter in the nervous system. [GOC:ef]

Glutamate secretion is a complex process essential for neuronal communication in the central nervous system. It involves the release of the neurotransmitter glutamate from presynaptic neurons into the synaptic cleft, where it binds to receptors on postsynaptic neurons, triggering a signal. Here's a detailed breakdown of the process:

1. **Synthesis and Packaging:** Glutamate is synthesized from glutamine, a precursor molecule, by the enzyme glutaminase. It is then packaged into synaptic vesicles, small membrane-bound sacs within the presynaptic neuron.
2. **Vesicle Transport and Docking:** Synaptic vesicles loaded with glutamate are transported to the presynaptic membrane, where they dock at specialized sites called active zones.
3. **Calcium Influx:** The arrival of an action potential at the presynaptic terminal triggers the opening of voltage-gated calcium channels. This allows a rapid influx of calcium ions (Ca2+) into the presynaptic terminal.
4. **Exocytosis:** The increase in intracellular calcium concentration triggers a cascade of events leading to the fusion of synaptic vesicles with the presynaptic membrane. This process, called exocytosis, releases glutamate into the synaptic cleft.
5. **Glutamate Receptor Binding:** Released glutamate diffuses across the synaptic cleft and binds to specific glutamate receptors on the postsynaptic neuron. There are two main types of glutamate receptors: ionotropic receptors (NMDA, AMPA, kainate) and metabotropic receptors (mGluRs).
6. **Postsynaptic Signaling:** Binding of glutamate to its receptors initiates a signaling cascade within the postsynaptic neuron. Ionotropic receptors, upon glutamate binding, open channels allowing ions to flow across the membrane, altering the postsynaptic neuron's electrical potential. Metabotropic receptors, on the other hand, trigger intracellular signaling pathways, leading to changes in neuronal activity.
7. **Glutamate Removal:** Glutamate is quickly removed from the synaptic cleft to prevent overstimulation of postsynaptic neurons. This is accomplished by two primary mechanisms:
- **Reuptake:** Glutamate transporters located on astrocytes and presynaptic neurons rapidly remove glutamate from the synapse and transport it back into the cell.
- **Enzymatic degradation:** The enzyme glutamine synthetase converts glutamate into glutamine within astrocytes, effectively terminating its activity.

This intricate process of glutamate secretion underlies a wide range of brain functions, including learning, memory, and synaptic plasticity. It's a crucial element in neuronal communication and plays a vital role in maintaining healthy brain function.'
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Proteins (5)

Compounds (219)