Recruitment of synaptic molecules during synaptogenesis.

The glutamatergic synapse is the main type of excitatory synapse in the mammalian brain. The formation of each glutamatergic synapse is associated with the recruitment of numerous (probably hundreds) different molecules and their assimilation into functional assemblies. Intense research has revealed the identity of many of these molecules, provided information as to interactions they are involved in, and offered clues as to their roles in synaptic function. Recent work has also begun to shed light on fundamental mechanisms underlying molecule recruitment to developing glutamatergic synapses. Current data indicate that the formation of presynaptic active zones-sites of neurotransmitter release-may be realized by the insertion of precursor vesicles containing multiple active zone components, possibly in pre-assembled form. The assembly of the postsynaptic reception apparatus, on the other hand, seems to occur via the sequential recruitment of molecules to the postsynaptic membrane and their assimilation in situ. Several molecules and mechanisms have been identified that display a capacity for inducing pre- or postsynaptic differentiation. These exciting findings are starting to provide a rudimentary framework for understanding key processes underlying the formation of glutamatergic synaptic connections.