In the central nervous system, mechanisms of postsynaptic clustering of neurotransmitter receptors are best understood at glycinergic inhibitory synapses. The glycine receptor is a pentameric protein composed of three α and two β transmembrane proteins: the ligand-binding α subunit and a structural β subunit. At glycinergic synapses, these receptors form clusters at the postsynaptic membrane directly opposite to the presynaptic release sites. Anchoring of glycine receptors in the neuronal membrane depends on a peripheral membrane protein named gephyrin. Gephyrin binds to the glycine receptor via the β subunit and links the receptor to the subsynaptic cytoskeleton. Gephyrin may be involved in the anchoring of other neurotransmitter receptors such as the γ-aminobutyric acid (GABA A ) receptor.