Gamma-aminobutyric acid (GABA) A receptor, alpha 5, also known as GABRA5, is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

which in humans is encoded by the ''GABRA5''

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...

Function

GABA is the major inhibitory neurotransmitter in the mammalian brain where it acts at GABA_A receptors, which are

ligand-gated 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 ...

chloride channel Chloride channels are a superfamily of poorly understood ion channels specific for chloride. These channels may conduct many different ions, but are named for chloride because its concentration ''in vivo'' is much higher than other anions. Severa ...

s. Chloride conductance of these channels can be modulated by agents such as

benzodiazepine Benzodiazepines (BZD, BDZ, BZs), sometimes called "benzos", are a class of depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed to treat conditions such as anxiety disorders, ...

s that bind to the GABA_A receptor. At least 16 distinct subunits of GABA_A receptors have been identified. Transcript variants utilizing three different alternative non-coding first

exon An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequen ...

s have been described.

Subunit selective ligands

Recent research has produced several ligands which are moderately selective for GABA_A receptors containing the α₅ subunit. These have proved to be useful in investigating some of the side effects of benzodiazepine and nonbenzodiazepine drugs, particularly the effects on learning and memory such as

anterograde amnesia In neurology, anterograde amnesia is the inability to create new memories after the event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact. T ...

. Inverse agonists at this subunit have

nootropic Nootropics ( , or ) (colloquial: smart drugs and cognitive enhancers, similar to adaptogens) are a wide range of natural or synthetic supplements or drugs and other substances that are claimed to improve cognitive function or to promote re ...

effects and may be useful for the treatment of cognitive disorders such as

Alzheimer's disease Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...

Agonists

QH-ii-066 QH-II-66 (QH-ii-066) is a sedative drug which is a benzodiazepine derivative. It produces some of the same effects as other benzodiazepines, but is much more selective than most other drugs of this class and so produces somewhat less sedation and ...

SH-053-R-CH3-2′F SH-053-R-CH3-2′F is a drug used in scientific research which is a benzodiazepine derivative. It produces some of the same effects as other benzodiazepines, but is much more subtype-selective than most other drugs of this class, having high sel ...

Antagonists

* α₅IA *

Basmisanil Basmisanil (; developmental codes RG-1662 and RO5186582) is a highly selective inverse agonist/negative allosteric modulator of α5 subunit-containing GABAA receptors which is under development by Roche for the treatment of cognitive impairmen ...

(RG-1662, RO5186582): derivative of Ro4938581, negative allosteric modulator at GABA_A α₅, in human trials for treating cognitive deficit in

Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual dis ...

. *

L-655,708 L-655,708 (FG-8094) is a nootropic drug invented in 1996 by a team working for Merck, Sharp and Dohme, that was the first compound developed which acts as a subtype-selective inverse agonist at the α5 subtype of the benzodiazepine binding sit ...

* MRK-016 *

PWZ-029 PWZ-029 is a benzodiazepine derivative drug with nootropic effects developed by WiSys,US Patent application US2006/258643 A1 It acts as a subtype-selective, mixed agonist-inverse agonist at the benzodiazepine binding site on the GABAA receptor ...

: moderate inverse agonist *

Pyridazine Pyridazine is an aromatic, heterocyclic, organic compound with the molecular formula . It contains a six-membered ring with two adjacent nitrogen atoms. It is a colorless liquid with a boiling point of 208 °C. It is isomeric with two other ...

s *

Ro4938581 Ro4938581 is a nootropic drug invented in 2009 by a team working for Hoffmann-La Roche, which acts as a subtype-selective inverse agonist at the α5 subtype of the benzodiazepine binding site on the GABAA receptor. It has good selectivity f ...

TB-21007 TB-21007 is a nootropic drug which acts as a subtype-selective inverse agonist at the α5 containing GABAA receptors Receptor may refer to: *Sensory receptor, in physiology, any structure which, on receiving environmental stimuli, produces a ...

References

External links

* Ion channels Biology of bipolar disorder {{membrane-protein-stub