Chemical synapses are highly specialized cell-cell junctions designed for e
fficient signaling between nerve cells. Distinct cytoskeletal matrices are
assembled at either side of the synaptic junction. The presynaptic cytomatr
ix at the active zone (CAZ) defines and organizes the site of neurotransmit
ter release from presynaptic nerve terminals. The postsynaptic density (PSD
) tethers neurotransmitter receptors and the postsynaptic signal transducti
on machinery. Recent progress in the identification and characterization of
novel CAZ and PSD components has revealed new insights into the molecular
organization and assembly mechanisms of the synaptic neurotransmission appa
ratus. On the presynaptic side, Bassoon and Piccolo, two related giant prot
eins, are crucially involved in scaffolding the CAZ. On the postsynaptic si
de, two families of multidomain adaptor proteins, the MAGuKs (membrane-asso
ciated guanylate kinase homologs) and the ProSAP (proline-rich synapse-asso
ciated protein, also termed Shank) family members are thought to be major o
rganizing molecules of the PSD.