Recent Structural Insights into the Molecular Architecture of Synapses

Synaptic transmission between pre- and postsynaptic neurons occurs when the presynaptic neuron terminal is temporarily depolarized upon action potential arrival, opening voltage-gated Ca²⁺ channels at synapses. Ca²⁺ will flow into the presynapse, and it will trigger the fusion of neurotransmitter-filled synaptic vesicles with the presynaptic membrane in less than a millisecond. Neurotransmitter molecules are then released into the synaptic cleft and bind to receptors in the postsynaptic membrane. Understanding the mechanisms that underlie this complex cellular process requires detailed knowledge of the spatial and structural organization of the macromolecular components of the synapse. This chapter focuses on recent structural insights into the presynaptic machinery and the spatial relationship between synaptic vesicles, presynaptic factors, and postsynaptic receptors.