Synaptotagmin in Ca2+ -dependent exocytosis: dynamic action in a flash

Synaptotagmins have been the popular candidates for the Ca2+ sensor that couples local rise in Ca2+ to neurotransmitter release. Studies in worm, fly, and mouse corroborate the likely role for synaptotagmin I, the best-studied synaptotagmin prototype, as a Ca2+ trigger for synaptic vesicle exocytosis. Recent investigations have focused on structural domains of synaptotagmin that are critical for its function. Here we provide a brief overview of synaptotagmin I and discuss recent studies within the framework of neurotransmitter release mechanisms for fast synaptic transmission.