Ionotropic glutamate receptors (iGluRs) are
ligand-gated ion channels
Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in res ...
that are activated by the
neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell.
Neu ...
glutamate
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synt ...
. They mediate the majority of excitatory
synaptic transmission throughout the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
and are key players in
synaptic plasticity, which is important for
learning
Learning is the process of acquiring new understanding, knowledge, behaviors, skills, values, attitudes, and preferences. The ability to learn is possessed by humans, animals, and some machines; there is also evidence for some kind of lea ...
and
memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remember ...
. iGluRs have been divided into four subtypes on the basis of their ligand binding properties (
pharmacology
Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...
) and
sequence
In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is called ...
similarity:
AMPA receptors,
kainate receptors,
NMDA receptors
The ''N''-methyl-D-aspartate receptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other two being AMPA and ...
and
delta receptors (see below).
AMPA receptors are the main charge carriers during basal transmission, permitting influx of
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
ions to depolarise the postsynaptic
membrane. NMDA receptors are blocked by
magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
ions and therefore only permit ion flux following prior depolarisation. This enables them to act as
coincidence detectors for synaptic plasticity. Calcium influx through NMDA receptors leads to persistent modifications in the strength of
synaptic transmission
Neurotransmission (Latin: ''transmissio'' "passage, crossing" from ''transmittere'' "send, let through") is the process by which signaling molecules called neurotransmitters are released by the axon terminal of a neuron (the presynaptic neuron ...
.
iGluRs are tetramers (they are formed of four subunits). All subunits have a shared architecture with four domain layers: two extracellular clamshell domains called the N-terminal domain (NTD) and ligand-binding domain (LBD; which binds glutamate), the transmembrane domain (TMD) that forms the
ion channel
Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ...
, and an intracellular C-terminal domain (CTD).
Human proteins/genes encoding iGluR subunits
AMPA receptors: GluA1/
GRIA1; GluA2/
GRIA2; GluA3/
GRIA3
Glutamate receptor 3 is a protein that in humans is encoded by the ''GRIA3'' gene.
Function
Glutamate receptors are the predominant excitatory neurotransmitter receptors in the mammalian brain and are activated in a variety of normal neurophy ...
; GluA4/
GRIA4;
delta receptors: GluD1/
GRID1; GluD2/
GRID2
Glutamate receptor, ionotropic, delta 2, also known as GluD2, GluRδ2, or δ2, is a protein that in humans is encoded by the ''GRID2'' gene. This protein together with GluD1 belongs to the delta receptor subtype of ionotropic glutamate receptor ...
;
kainate receptors: GluK1/
GRIK1; GluK2/
GRIK2; GluK3/
GRIK3; GluK4/
GRIK4
GRIK4 (''glutamate receptor, ionotropic, kainate 4'') is a kainate receptor subtype belonging to the family of ligand-gated ion channels which is encoded by the gene.
Function
This gene encodes a protein that belongs to the glutamate-gated ion ...
; GluK5/
GRIK5;
NMDA receptors
The ''N''-methyl-D-aspartate receptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other two being AMPA and ...
: GluN1/
GRIN1; GluN2A/
GRIN2A
Glutamate MDAreceptor subunit epsilon-1 is a protein that in humans is encoded by the ''GRIN2A'' gene. The canonical GluN2A subunit isoform encompasses 1464 amino acids. Alternative splicing can generate a primate-specific GluN2A-short isoform (1 ...
; GluN2B/
GRIN2B
Glutamate MDAreceptor subunit epsilon-2, also known as ''N''-methyl D-aspartate receptor subtype 2B (NMDAR2B or NR2B), is a protein that in humans is encoded by the ''GRIN2B'' gene.
NMDA receptors
''N''-methyl-D-aspartate ( NMDA) receptors are ...
; GluN2C/
GRIN2C
Glutamate MDAreceptor subunit epsilon-3 is a protein that in humans is encoded by the ''GRIN2C'' gene.
Function
N-methyl-D-aspartate (NMDA) receptors are a class of ionotropic glutamate receptors. NMDA channel has been shown to be involved i ...
; GluN2D/
GRIN2D
Glutamate MDAreceptor subunit epsilon-4 is a protein that in humans is encoded by the ''GRIN2D'' gene.
Function
N-methyl-D-aspartate (NMDA) receptors are a class of ionotropic glutamate receptors. NMDA channel has been shown to be involved in ...
; GluN3A/
GRIN3A; GluN3B/
GRIN3B
Glutamate MDAreceptor subunit 3B is a protein that in humans is encoded by the ''GRIN3B'' gene.
See also
* NMDA receptor
The ''N''-methyl-D-aspartate receptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and ion cha ...
;
References
Protein domains
Protein families
Membrane proteins
Ionotropic glutamate receptors
{{membrane-protein-stub