GRIK4 is a kainate receptor

Kainate receptor

Kainate receptors, or KARs, are non-NMDA ionotropic receptors which respond to the neurotransmitter glutamate. They were first identified as a distinct receptor type through their selective activation by the agonist kainate, a drug first isolated from red algae Digenea simplex. KARs are less well...

 subtype belonging to the family of ligand-gated ion channel

Ligand-gated ion channel

Ligand-gated ion channels are one type of ionotropic receptor or channel-linked receptor. They are a group of transmembrane ion channels that are opened or closed in response to the binding of a chemical messenger , such as a neurotransmitter.The binding site of endogenous ligands on LGICs...

s which is encoded by the gene.

Function

This gene encodes a protein that belongs to the glutamate-gated

Glutamate receptor

Glutamate receptors are synaptic receptors located primarily on the membranes of neuronal cells. Glutamate is one of the 20 amino acids used to assemble proteins and as a result is abundant in many areas of the body, but it also functions as a neurotransmitter and is particularly abundant in the...

 ionic channel family. Glutamate

Glutamic acid

Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...

 functions as the major excitatory neurotransmitter

Neurotransmitter

Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

 in the central nervous system through activation of ligand-gated ion channels and G protein-coupled membrane receptors. The protein encoded by this gene forms functional heteromeric kainate-preferring ionic channels with the subunits encoded by related gene family members.

Clinical signficance

A single nucleotide polymorphism

Single nucleotide polymorphism

A single-nucleotide polymorphism is a DNA sequence variation occurring when a single nucleotide — A, T, C or G — in the genome differs between members of a biological species or paired chromosomes in an individual...

 (rs1954787

Rs1954787

Rs1954787 is a gene variation, a single nucleotide polymorphism in the GRIK4 gene.A study has reported that this polymorphism is associated with success of antidepressant treatment....

) in the GRIK4 gene has shown a treatment-response-association with antidepressant

Antidepressant

An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes people with a depressive illness will experience a therapeutic effect to their mood;...

 treatment.

Variation in GRIK4 have been associated with both increased and decreased risk of bipolar disorder

Bipolar disorder

Bipolar disorder or bipolar affective disorder, historically known as manic–depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or...

. A possible mechanism for this observation is that the sequence variation influences secondary structures

RNA structure

Biomolecular structure is the structure of biomolecules, mainly proteins and the nucleic acids DNA and RNA. The structure of these molecules is frequently decomposed into primary structure, secondary structure, tertiary structure, and quaternary structure. The scaffold for this structure is...

 in the 3' UTR.

Interfering with GRIK4/KA1 function with a specific anti-KA1 antibody protects against kainate-induced neuronal cell death.

Evolutionary significance

The GRIK4 gene displayed significantly higher rates of evolution in primates than in rodents and especially in the lineage leading from primates to humans. Furthermore the GRIK4 gene is implicated in the development of the nervous system. Hence evolution of the GRIK4 gene is thought to have played a role in the dramatic increases in size and complexity of the brain that occurred during evolutionary history leading to humans.