Ligand Gated Ion Channels Receptors and There Roles Overview

Ligand gated ion channels (LGIC) build up a signification class of plasma membrane proteins admittable as critical for mediating cell-cell communication and cellular excitability.

Ligand-gated ion channels also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins that open to allow ions like K+, Na+, Ca2+, and/or Cl− to pass through the membrane in response to the binding of a chemical messenger like a neurotransmitter.

Therefore, when a presynaptic neuron is excited, then it releases a neurotransmitter from vesicles into the synaptic cleft. furthermore, the neurotransmitter then binds to the receptors located on the postsynaptic neuron. if these receptors are ligand gated ion channels, occurring the conformational change opens the ion channels, and therefore, leads to a flow of ions across the cell membrane. This, in turn, results in either a depolarization, for an inhibitory response, for an excitatory receptor response, or a hyperpolarization.

These receptor proteins are typically composed of a minimum of 2 different domains: a transmembrane domain and which includes the extracellular domain and an ion pore, which includes the ligand binding location. furthermore, this modularity has enabled a ‘divide and conquers’ approach and it used to find the structure of the proteins. These functions of such receptors located at synapses, and which is to convert the chemical signal of presynaptically released neurotransmitters directly and quickly into a postsynaptic electrical signal. furthermore, several LICs are except modulated by allosteric ligands, by the channel blockers, membrane potential, or ions. Therefore, LICs are divided into three(3) super families that lack derivationist relationship: cys-loop receptors, ATP-gated channels, and ionotropic glutamate receptors.

Receptor Types and Subtypes

Ligand-gated ion channels are large, multisubunit receptors that, therefore, form a membrane ion channel that, when open, allows the passage of K+, Na+, Ca++, or Cl−. Furthermore, when once the channel/receptor complex is activated, then the membrane potential may become hyperpolarized or depolarized depending on the direction of the ion flow and the ion involved. Therefore, typically, each subunit contains 4 hydrophobic transmembrane domains linked by hydrophilic groups. thus the activation of these channels leads to a rapid response, allowing ions to flow down their electrochemical gradients. Nicotinic cholinergic, 5-hydroxytryptamine3 (5HT3), and GABA-A receptor are examples of ligand-gated ion channel sites.

Ion Channels

Ligand gated ion channels are activated upon the binding of a neurotransmitter to the ion channel and are involved in fast synaptic transmission in the nervous system. Many of the ion channels in the given below table have a wide tissue distribution outside of the nervous system and have other functions beyond the synaptic transmission. Therefore, these neurotransmitters include acetylcholine, γ-aminobutyric acid (GABA), glycine, and serotonin (5-hydroxytryptophan), glutamate, and the ion channels are more commonly referred to as receptors. Furthermore, these neurotransmitters also activate a second distinct type of receptor. Therefore, this second receptor type is a heptahelical receptor which produces the intracellular second messengers through the modulation of G proteins. Furthermore, in the context of glutamate receptors the most commonly, the ligand-gated ion channel is referred to as an ionotropic receptor, whereas the G protein-coupled receptor is referred to as a metabotropic receptor. Familiarity with the nomenclature is helpful in determining whether a neurotransmitter receptor is ionotropic or metabotropic.

On the basis of sequence similarity, therefore, it had been supposed that these ligand gated ion channels formed one superfamily. furthermore, the present view is those glutamate receptors have a different transmembrane topology and belong to a distinct family of ligand-gated ion channels.

The nicotinic acetylcholine receptor is a pentamer, and therefore every subunit contains four transmembrane segments with the N and C termini outside of the membrane. Therefore, among ligand-gated ion channels, the nicotinic acetylcholine receptor has been the foremost characterized. furthermore, this is mostly because of the very fact that the Torpedo electric ray has been a source of abundant amounts of the protein and this receptor mediates synaptic transmission at the neuromuscular junction, therefore, which is a synapse that has been amenable to biophysical studies. furthermore, at the neuromuscular junction, the acetylcholine is liberated from the motoneuron and diffuses across the synaptic cleft to activate the receptor. therefore, the opening of ion channels which depolarizes the membrane and generates an action potential in the muscle which initiates muscle contraction.

Ligand Gated Ion Channel Receptors

This type of swift response is the view, as an example, in neuromuscular junctions, where muscle cells reply to an intimation from the neighboring nerve cell. Therefore, the nerve cell discharges a neurotransmitter signal into the synaptic cleft, that is that the space between the muscle cell and the nerve cell it is “talking to”. Examples of neurotransmitter signal molecules are serotonin and acetylcholine. as shown in given below figure.

When acetylcholine molecules are released into the synaptic cleft (therefore, these space between the pre- and post-synaptic cells) they diffuse rapidly till they reach their receptors on the membrane of the muscle cell. furthermore, the binding of the acetylcholine to its receptor, an ion channel on the membrane of the muscle cell, causes the gate within the ion channel to open. Therefore, the ion flow through the channel can instantly change the membrane potential. This, in bend, can trigger other changes in a cell. The speed with which changes are brought about in neurotransmitter signaling is evident when you consider how quickly you remove your hand from a hot surface. furthermore, sensory neurons carry data to the brain from your hand on the hot surface, and motor neurons signal to your muscles to move the hand, in less time than it took you to scan this sentence.

Ligand Gated Ion Channel Interacting Proteins And Their Role In Neuroprotection

Ion channel receptors are a vital component of nervous system signaling, permitting rapid and direct conversion of a chemical neurotransmitter message to an electrical current. Furthermore, in recent decades, it’s become apparent that ionotropic receptors are regulated by protein-protein interactions with alternative ion channels, G-protein coupled receptors, and therefore, intracellular proteins and other proteins may also are combining by these interactions with ion channel receptors. furthermore, this bidirectional functional cross-talk is for cellular functions like disease states and excitotoxicity in pathological like stroke, and for dynamics of activity-dependent synaptic plasticity. Protein interactions with ion channel receptors will so increase the efficiency of neuronal signaling cascades and describe a unique target for therapeutic intervention in neuropsychiatric disease. This review can highlight a few examples of ion channel receptor interactions and therefore, their potential clinical utility for neuroprotection.

Therefore, the accomplished neurotransmission needs the precise interplay of different neurotransmitter receptors at pre- and post-synaptic compartments. The ligand-gated ion channels play a central role in intercellular communication within the nervous system. Ligand gated ion channels are oligomeric protein assemblies to transform a chemical signal into an ion flux through the post-synaptic membrane and therefore, are involved in the brain functions like learning, memory., and attention. Therefore, the ion channels are the cellular appliance for ion flux across the membrane and electrical excitation of neurons.

REFERENCES

1. Ligand-gated ion channel From Wikipedia https://en.wikipedia.org/wiki/Subdural_hygroma
2. Ligand-gated Ion Channel Receptors Article taken from the libretexts
3. Ligand-gated ion channel interacting proteins: a comparative study
4. Mary A. Pacheco, in xPharm: The Comprehensive Pharmacology Reference, 2007
5. B. Alexander Yi, Lily Y. Jan, in Encyclopedia of the Human Brain, 2002
6. Collingridge GL, Olsen RW, Peters J, Spedding M (January 2009).