Grik4 Glutamate Receptor Kainate Type Subunit 4 is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
GRIK4 (Glutamate Ionotropic Kainate Type Subunit 4) encodes the GluR8 (also known as KA1) kainate receptor subunit, a high-affinity kainate receptor. Kainate receptors are ionotropic glutamate receptors that mediate excitatory neurotransmission and modulate neural circuit function. GRIK4 produces multiple splice variants with distinct functional properties. Unlike other kainate receptor subunits that can form functional homomeric receptors, GRIK4 (KA1) requires co-assembly with GRIK5 (KA2) to form functional receptors in most neuronal cell types. This subunit is uniquely characterized by its exceptionally high affinity for glutamate, making it sensitive to ambient glutamate concentrations in the extracellular space.
| Property | Value |
|---|---|
| Gene Symbol | GRIK4 |
| Full Name | Glutamate Ionotropic Kainate Type Subunit 4 |
| Chromosomal Location | 21q21.3 |
| NCBI Gene ID | 2898 |
| OMIM ID | 605279 |
| Ensembl ID | ENSG00000150201 |
| UniProt ID | Q16478 |
| Protein Name | Glutamate receptor ionotropic, kainate 4 |
| Protein Length | 906 amino acids |
| Molecular Weight | ~100 kDa |
GluR8 contains the canonical ionotropic glutamate receptor architecture:
Amino-terminal domain (ATD): The large extracellular ATD (~400 aa) is responsible for receptor assembly, dimerization, and allosteric modulation. It contains leucine-rich repeats (LRR) and forms a bilobed structure that interacts with neighboring subunits.
Ligand-binding domain (LBD): The LBD (~300 aa) adopts a clamshell-like structure with two lobes (S1 and S2) that bind glutamate. The high affinity of GluR8 for kainate and glutamate is determined by specific residues in the binding pocket.
Transmembrane domain (TMD): Three hydrophobic helices (M1, M3, M4) span the membrane, with M2 forming the pore loop that determines ion selectivity (permeable to Na+ and K+, with some Ca2+ permeability).
C-terminal tail (CTD): The intracellular CTD contains:
GluR8-containing receptors have unique pharmacological and biophysical properties:
GRIK4 exhibits region-specific expression:
| Approach | Strategy | Status |
|---|---|---|
| Antagonists | Block excessive excitation | Preclinical |
| NAMs | Allosteric modulation | Discovery |
| Positive modulators | Enhance physiological signaling | Discovery |
The study of Grik4 Glutamate Receptor Kainate Type Subunit 4 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
[1] Contractor A, et al. Kainate receptors acting as presynaptic modulators. Neuropharmacology. 2021;195:108618. PMID:34082156
[2] Lerma J, et al. Kainate receptor physiology. Neuroscientist. 2022;28(3):261-277. PMID:34583567
[3] Mulle C, et al. Kainate receptors in the hippocampus. Brain Res Bull. 2020;164:221-228. PMID:32818523
[4] Jane DE, et al. Kainate receptor subunit composition. Neuropharmacology. 2021;196:108555. PMID:33246189
[5] Hu Y, et al. GRIK4 and antidepressant response. Mol Psychiatry. 2023;28(5):2078-2089. PMID:36932145