Glutamate receptor, metabotropic 6, also known as GRM6 or mGluR6, is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

which in humans is encoded by the ''GRM6''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

Function

L-

glutamate Glutamic acid (symbol Glu or E; known as glutamate in its anionic form) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a Essential amino acid, non-essential nutrient for humans, meaning that ...

is the major excitatory

neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotra ...

in the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

and activates both ionotropic and metabotropic glutamate receptors. Glutamatergic neurotransmission is involved in most aspects of normal brain function and can be perturbed in many neuropathologic conditions. The

metabotropic glutamate receptor The metabotropic glutamate receptors, or mGluRs, are a type of glutamate receptor that are active through an indirect metabotropic receptor, metabotropic process. They are members of the group C GPCR family, group C family of G-protein-coupled r ...

s are a family of

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily related ...

s, that have been divided into 3 groups on the basis of sequence homology, putative signal transduction mechanisms, and pharmacologic properties. Group I includes

GRM1 The glutamate receptor, metabotropic 1, also known as GRM1, is a human gene which encodes the metabotropic glutamate receptor 1 (mGluR1) protein. Function L-Glutamate is the major excitatory neurotransmitter in the central nervous system and ...

and

GRM5 Metabotropic glutamate receptor 5 is an excitatory Gq-coupled G protein-coupled receptor predominantly expressed on the postsynaptic sites of neurons. In humans, it is encoded by the ''GRM5'' gene. Function The amino acid L-glutamate is the ...

and these receptors have been shown to activate

phospholipase C Phospholipase C (PLC) is a class of membrane-associated enzymes that cleave phospholipids just before the phosphate group (see figure). It is most commonly taken to be synonymous with the human forms of this enzyme, which play an important role i ...

. Group II includes

GRM2 Metabotropic glutamate receptor 2 (mGluR2) is a protein that, in humans, is encoded by the ''GRM2'' gene. mGluR2 is a G protein-coupled receptor (GPCR) that couples with the Gi alpha subunit. The receptor functions as an autoreceptor for glutamat ...

and GRM3, while Group III includes

GRM4 Metabotropic glutamate receptor 4 is a protein that in humans is encoded by the ''GRM4'' gene. Together with GRM6, GRM7 and GRM8 it belongs to Metabotropic glutamate receptor#Group II and Group III, group III of the metabotropic glutamate recep ...

, GRM6,

GRM7 Metabotropic glutamate receptor 7 is a protein that in humans is encoded by the ''GRM7'' gene. Function L-glutamate is the major excitatory neurotransmitter in the central nervous system and activates both ionotropic and metabotropic glutama ...

and GRM8. Group II and III receptors are linked to the inhibition of the

cyclic AMP Cyclic adenosine monophosphate (cAMP, cyclic AMP, or 3',5'-cyclic adenosine monophosphate) is a second messenger, or cellular signal occurring within cells, that is important in many biological processes. cAMP is a derivative of adenosine triph ...

cascade but differ in their agonist selectivities. mGluR6 is specifically expressed in the retina, in a subtype of bipolar cells that depolarize in response to light, known as ON bipolar cells. These cells form

synapses In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...

with photoreceptor cells, and detect the

glutamate via a GPCR signal transduction cascade. The glutamate receptor mGluR6 is located post-synaptically at the tips of the bipolar cell

dendrites A dendrite (from Greek δένδρον ''déndron'', "tree") or dendron is a branched cytoplasmic process that extends from a nerve cell that propagates the electrochemical stimulation received from other neural cells to the cell body, or soma ...

, and is responsible for initiating a signaling cascade that ultimately controls gating of the

TRPM1 Transient receptor potential cation channel subfamily M member 1 is a protein that in humans is encoded by the ''TRPM1'' gene. Function The protein encoded by this gene is a member of the transient receptor potential (TRP) family of non-select ...

channel. In human patients, mutations in the ''GRM6'' gene are associated with

congenital stationary night blindness Congenital stationary night blindness (CSNB) is a rare non-progressive retinal disorder. People with CSNB often have difficulty adapting to low light situations due to impaired photoreceptor transmission. These patients may also have reduced visu ...

Function

See also

References

Further reading