Overview: Presynaptic terminal proteins orchestrate stepwise synaptic vesicle phases

In mammalian central and peripheral nervous systems, most of presynaptic terminals operate as follows. Synaptic vesicles docked and primed at the active zone are ready for exocytosis and form a synaptic vesicle pool, the readily releasable pool. Neural electrical signal, an action potential, reached to the presynaptic nerve terminal induces the opening of voltage-gated Ca channels and a rapid influx of Ca at the active zone. The Ca transient at the active zone triggers neurotransmitters release by synaptic vesicle exocytosis and controls the release efficacy for incoming neuronal signals. After exocytosis, the synaptic vesicle membrane is recycled from the nerve terminal membrane by endocytosis. Renewal synaptic vesicles are filled with transmitter and reserved in a pool, the reserve pool. Storage of synaptic vesicles in the pools and the mobilization from the presynaptic membrane and the reserve pool are controlled by Ca signals after action potential firing. How synaptic vesicles in each phase are controlled? Studies over the last 25 years have revealed that individual proteins in the presynaptic terminal form complexes and orchestrate each of the synaptic vesicle phases and that Ca sensor proteins promote synaptic vesicle in a phase to a next stage of the phase along the maturation pathway. To understand presynaptic terminals, in this book, specialists for presynaptic protein(s) illustrate in detail the involvement and the regulation in each synaptic vesicle phase. This overview chapter shortly follows, step by step, the synaptic vesicle phases in mammalian presynaptic terminals.