The role of glycosylation in ionotropic glutamate receptor ligand binding,function, and trafficking

Members of the ionotropic glutamate receptor (iGluR) family have between 4 and 12 consensus asparagine (N)-linked glycosylation sites. They are locali zed on the extracellular N-termini, and the loop between the penultimate an d last transmembrane domains. These regions also contain the essential elem ents for formation of the ligand binding site. N-linked glycosylation does not appear to be essential for formation of the ligand binding site per se, but there are demonstrated interactions between glycosylation state and li gand binding affinity, receptor physiology, susceptibility to allosteric mo dulation and, in some cases, trafficking. There is no indication of a gener al role for N-linked glycosylation in iGluRs; instead the effects of glycos ylation vary among glutamate receptor subtypes and splice variants, with sp ecific effects on structure or function with different subunits.