Glycine

The glycine receptor, or GlyR, is the receptor for the amino acid neurotransmitter glycine. It is one of the most widely distributed inhibitory receptors in the central nervous system and has important roles in a variety of physiological processes, especially in mediating inhibitory neurotransmission in the spinal cord and brain stem.^[1]

[edit] Activation and inactivation

The receptor can be activated by a range of simple amino acids including glycine, β-alanine and taurine, and can be selectively blocked by the high-affinity competitive antagonist strychnine.^[2] Caffeine has recently been found also to be a competitive antagonist.^[3]

[edit] Arrangement of subunits

Strychnine-sensitive glycine receptors are members of a family of Ligand-gated ion channels. Receptors of this family are arranged as five subunits surrounding a central pore, with each subunit composed of four α helical transmembrane segments.^[4]

There are presently four known isoforms of the α-subunit (α_1-4) of GlyR that are essential to bind ligands (GLRA1, GLRA2, GLRA3, GLRA4) and a single β-subunit (GLRB).

The adult form of the GlyR is the heteromeric α₁β receptor, which is believed to have a stoichiometry (proportion) of three α₁ subunits and two β subunits ^[5] or four α₁ subunits and one β subunit.^[6] The α-subunits are also able to form functional homo-pentameric receptors in heterologous expression systems in African clawed frog's oocytes or mammalian cell lines,^[6] and the α₁ homomeric receptor is essential for studies of channel pharmacokinetics and pharmacodynamics.^[7]

[edit] Glycine receptors in diseases

Disruption of GlyR surface expression or reduced ability of expressed GlyRs to conduct chloride ions results in the rare neurological disorder, hyperekplexia. The disorder is characterized by an exaggerated response to unexpected stimuli which is followed by a temporary but complete muscular rigidity often resulting in an unprotected fall. Chronic injuries as a result of the falls are symptomatic of the disorder.^[1] A mutation in GLRA1 is responsible for some cases of stiff person syndrome.^[8]

[edit] Research

Quantum dots have been used to track the diffusion of glycine receptors into the synapse of neurons.^[9]

[edit] Ligands

[edit] Agonists

• Alanine
• Cycloserine
• Dimethylglycine
• Glycine
• Hypotaurine
• Methylglycine (Sarcosine)
• Serine
• Taurine
• Trimethylglycine (Betaine)

[edit] Antagonists

• Brucine
• Gelsemine
• Gelseminine
• Strychnine
• Tutin

[edit] References

[edit] External links

• MeSH Glycine+Receptors