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 Gi protein alpha subunit is a family of heterotrimeric G protein alpha subunits. This family is also commonly called the Gi/o (Gi /Go ) family or Gi/o/z/t family to include closely related family members. G alpha subunits may be referred ...

. The receptor functions as an autoreceptor for

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 syn ...

, that upon activation, inhibits the emptying of vesicular contents at the presynaptic terminal of glutamatergic neurons.

Structure

In humans, mGluR2 is encoded by the ''GRM2'' gene on chromosome 3. At least three protein-coding isoforms are predicted based on genomic information, as well as numerous non-coding isoforms. The mGluR2 protein is a seven-pass transmembrane protein.

Function

In humans, mGluR2 is only expressed in the brain, and not in any other tissue. In the brain, mGluR2 is expressed in neurons as well as astrocytes. Subcellularly, mGluR2 is predominantly positioned at the presynaptic terminal, although it is also expressed at the

postsynaptic terminal Axon terminals (also called synaptic boutons, terminal boutons, or end-feet) are distal terminations of the telodendria (branches) of an axon. An axon, also called a nerve fiber, is a long, slender projection of a nerve cell, or neuron, that condu ...

. The metabotropic glutamate receptors are a family of G protein-coupled receptors, that have been divided into 3 groups on the basis of sequence homology, putative signal transduction mechanisms, and pharmacologic properties: Group I includes GRM1 and GRM5 and these receptors have been shown to activate phospholipase C. Group II includes mGluR2 (this receptor) and GRM3 while Group III includes GRM4, GRM6, GRM7 and GRM8. Group II and III receptors are linked to the inhibition of the cyclic AMP cascade but differ in their agonist selectivities.

Protein–protein interactions

mGluR2 is able to form a heteromeric complex with various other different GPCRs. One example is with isoform mGluR4. The mGluR2-mGluR4 heteromer exhibits a pharmacological profile distinct from the parent receptor monomers. Another example is with serotonin receptor 2A (5HT2A); see below.

Pharmacology

The development of subtype-2-selective

positive allosteric modulators In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimulus. Some of them, like benzodiazepines, are drugs. The site that an allosteric modulator binds t ...

(PAMs) experienced steady advance in recent years. mGluR2 potentiation is a new approach for the treatment of schizophrenia. On the other hand, antagonists and negative allosteric modulators of mGluR_2/3 have potential as

antidepressant Antidepressants are a class of medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common side-effects of antidepressants include dry mouth, weight gain, dizziness, hea ...

drugs.

Agonists

* Compound 1d (see reference) * LY-2812223

PAMs

* JNJ-46356479 * JNJ-40411813 *GSK-1331258 *Imidazo

,2-''a'' The comma is a punctuation mark that appears in several variants in different languages. It has the same shape as an apostrophe or single closing quotation mark () in many typefaces, but it differs from them in being placed on the baseline o ...

yridines *3-Aryl-5-phenoxymethyl-1,3-oxazolidin-2-ones *3-(Imidazolyl methyl)-3-aza-bicyclo .1.0exan-6-yl)methyl ethers: potent, orally stable * BINA: potent; modest ago-allosteric modulator; robust in-vivo activity. * LY-487,379: devoid of orthosteric activity; along with related 3-pyridylmethylsulfonamides the first subtype-2-selective potentiator published (2003).

Antagonists

LY-341,495 LY-341495 is a research drug developed by the pharmaceutical company Eli Lilly, which acts as a potent and selective orthosteric antagonist for the group II metabotropic glutamate receptors ( mGluR2/3). It is used in scientific research in sever ...

* MGS-0039 * EGLU

NAMs

* 7,8-dichloro-4-

-(2-methylpyridin-4-yl)phenyl The hyphen-minus is the most commonly used type of hyphen, widely used in digital documents. It is the only character that looks like a minus sign or a dash in many character sets such as ASCII or on most keyboards, so it is also used as such. ...

1,3-dihydro-1,5-benzodiazepin-2-one and related compounds. * MNI-137 - 8-bromo-4-(2-cyanopyridin-4-yl)-1H-benzo 1,4]diazepin-2(3H)-one *

RO4491533 RO-4491533 is a drug developed by Hoffmann-La Roche which acts as a potent and selective negative allosteric modulator for group II of the metabotropic glutamate receptors ( mGluR2/3), being equipotent at mGluR2 and mGluR3 but without activit ...

- 4-

-(2,6-dimethylpyridin-4-yl)phenyl The hyphen-minus is the most commonly used type of hyphen, widely used in digital documents. It is the only character that looks like a minus sign or a dash in many character sets such as ASCII or on most keyboards, so it is also used as such. ...

7-methyl-8-trifluoromethyl-1,3-dihydrobenzo 1,4]diazepin-2-one

Role in hallucinogenesis

Many psychedelic drug, psychedelic drugs (e.g. LSD-25) produce their effects by binding to the oligomerized complexes of the

5HT2A The 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor (GPCR). The 5-HT2A receptor is a cell surface receptor, but has several intracellular locations. 5-HT is sh ...

and mGlu2 receptors.

Lisuride Lisuride, sold under the brand name Dopergin among others, is a monoaminergic medication of the ergoline class which is used in the treatment of Parkinson's disease, migraine, and high prolactin levels. It is taken by mouth. Side effects of lis ...

acts preferentially or exclusively on the non-heteromerized 5HT2A receptors, which are not capable of inducing psychedelic effects. Due to this, lisuride is capable of reducing the hallucinogenic effects of these drugs through competitive antagonistic activity (producing the effect of a silent antagonist in the presence of these drugs). Strong agonists for either subunit of the 5HT2A-mGlu2R heterocomplex suppress signaling through the partner subunit and

inverse agonist In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse agon ...

s for either subunit potentiate the signaling through the partner subunit.

Role in rabies virus infection

mGluR2 has been found to be a novel receptor for rabies virus. The virus has a glycoprotein on its surface which interacts with the receptor. Rabies virus can bind to mGLuR2 directly and the virus-receptor complex is internalized into the cell together. The complex is then transported into early and late endosomes. Rabies virus enters the cells by

clathrin-independent endocytosis Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested material. E ...

which could suggest that mGLuR2 also uses this pathway. It is still to be clarified whether the Rabies virus glycoprotein can act as a PAM or NAM and in such a way affect the function of the receptor.

References

External links

* {{Metabotropic glutamate receptor modulators Metabotropic glutamate receptors