Assembly and forward trafficking of NMDA receptors (Review)

N-Methyl-D-aspartate (NMDA) receptors are a subclass of the excitatory, ionotropic L-glutamate neurotransmitter receptors. They are important for normal brain function being both primary candidates for the molecular basis of learning and memory and in the establishment of synaptic connections during the development of the central nervous system. NMDA receptors are also implicated in neurological and psychiatric disorders. Their dysfunction which is primarily due to either hypo- or hyper-activity is pivotal to these pathological conditions. There is thus a fine balance between NMDA receptor-mediated mechanisms in normal brain and those in diseased states where receptor homeostasis is perturbed. Receptor activity is due in part to the number of surface expressed receptors. Understanding the assembly and trafficking of this complex, heteromeric, neurotransmitter receptor family may therefore, be pivotal to understanding diseases in which their altered activity is evident. This article will review the current understanding of the mechanisms of NMDA receptor assembly, how this assembly is regulated and how assembled receptors are trafficked to their appropriate sites in post-synaptic membranes where they are integral components of a macromolecular signalling complex.