ABSTRACT
GABAA receptors are part of a family originally referred to as Cys-loop receptors, due to the presence of a highly conserved disulde bridge located in receptor subunits’ extracellular domain (ECD). Members of this family include nicotinic acetylcholine receptors (nAChRs), type 3 5-hydroxytryptamine receptors (5HT3Rs), γ-aminobutyric acid receptors (types A and C,
GABAA/CR), and glycine receptors (GlyRs) (Grenningloh et al., 1987; Betz, 1990). Also included are the Zn2+-activated cation channel (ZAC) (Davies et al., 2003) and invertebrate receptors activated either by glutamate or serotonin (anionic channels) or GABA (cationic channels) (Ortells and Lunt, 1995; Lester et al., 2004). However, recently, related bacterial homologues from Gloeobacter violaceus (GLIC) (Bocquet et al., 2009) and Erwinia chrysanthemi (ELIC) (Hilf and Dutzler, 2008) have been added to the family, but they lack the characteristic Cys-loop signature. As a consequence, Cys-loop receptors are now referred to as pentameric ligand-gated ion channels (pLGICs) to which we can also add the glutamate-activated Cl-channel (GluCl) from Caenorhabditis elegans (Hibbs and Gouaux, 2011).
