glutamate secretion, neurotransmission

Definition

Target type: biologicalprocess

The controlled release of glutamate by a cell, in which the glutamate acts as a neurotransmitter. [GOC:dph]

Glutamate secretion, a crucial process in neuronal communication, involves a complex interplay of intracellular signaling pathways, vesicle trafficking, and membrane fusion. Here's a detailed breakdown:

1. **Glutamate Synthesis and Packaging:**
- Glutamate, the primary excitatory neurotransmitter in the central nervous system, is synthesized from glutamine by the enzyme glutaminase within presynaptic neurons.
- Synthesized glutamate is then actively transported into synaptic vesicles, small membrane-bound sacs that store neurotransmitters. This transport is mediated by vesicular glutamate transporters (VGLUTs), ensuring high concentrations of glutamate within the vesicles.

2. **Action Potential Arrival and Calcium Influx:**
- When an action potential arrives at the presynaptic terminal, it triggers the opening of voltage-gated calcium channels.
- Calcium ions (Ca2+) rapidly influx into the presynaptic terminal, acting as a critical signal for neurotransmitter release.

3. **Vesicle Docking and Fusion:**
- The influx of Ca2+ initiates a cascade of molecular events leading to the fusion of glutamate-filled vesicles with the presynaptic membrane.
- Synaptotagmin, a Ca2+-binding protein, plays a key role in this process by sensing Ca2+ levels and mediating vesicle docking and fusion.
- Other proteins, including SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors), also contribute to the precise docking and fusion of vesicles with the presynaptic membrane.

4. **Glutamate Release into Synaptic Cleft:**
- Upon fusion, the vesicle membrane merges with the presynaptic membrane, releasing glutamate into the synaptic cleft, the narrow space between the presynaptic and postsynaptic neurons.
- This release of glutamate is a rapid and highly regulated process, ensuring precise neurotransmission.

5. **Glutamate Receptor Activation:**
- Glutamate released into the synaptic cleft binds to glutamate receptors on the postsynaptic neuron.
- These receptors, including AMPA, NMDA, and kainate receptors, are ionotropic, meaning they directly open ion channels upon glutamate binding.
- This opening allows ions like sodium and calcium to flow into the postsynaptic neuron, triggering an excitatory postsynaptic potential (EPSP) and ultimately contributing to neuronal signaling.

6. **Glutamate Clearance and Recycling:**
- To ensure precise and efficient neurotransmission, glutamate is rapidly removed from the synaptic cleft after release.
- This removal is achieved by glutamate transporters, which actively transport glutamate back into presynaptic neurons or into surrounding glial cells.
- Glial cells can then convert glutamate back into glutamine, which is transported back to presynaptic neurons, completing the cycle.

7. **Regulation of Glutamate Secretion:**
- Glutamate secretion is tightly regulated by various mechanisms, including presynaptic autoreceptors, feedback loops, and intracellular signaling pathways.
- These mechanisms ensure that glutamate release occurs at appropriate levels and in response to specific neuronal activity, preventing excessive excitation or neurotoxicity.'
"

Proteins (2)

Compounds (17)