Drosophila active zones: From molecules to behaviour.

In a constantly changing environment, neuronal circuits need to be updated and adjusted to elicit directed actions. Synaptic plasticity plays an important role in modulating such globally and locally acting networks. The active zone (AZ) is a protein-rich compartment of chemical synapses, where precisely orchestrated molecular interactions control synaptic vesicle (SV) fusion with the presynaptic membrane. The subsequent release of neurotransmitter substances onto postsynaptic receptor fields forms the basis of neuronal communication. Structural, functional and molecular features of AZs can differ significantly between systems, within one and the same neuron and at an individual site over time. Moreover, the properties of an AZ can be altered by changes in cellular activity. While it is recognized that such AZ plasticity modulates synaptic communication, our mechanistic understanding of its impact on neural network function and animal behaviour is far from complete. Research on Drosophila melanogaster has created an advantageous situation for investigating molecular mechanisms of AZ physiology in a behavioural context. The sophisticated genetic tools and excellent experimental accessibility of the fruit fly can now be combined with detailed anatomical information on the nervous system and quantifiable readouts of various behaviours at high resolution. Here, we review molecular studies of AZ structure and function at the neuromuscular junction (NMJ) and consider how mechanisms identified in the periphery may relate to the operation of central AZs. Our discussion emphasizes that the location of AZs in central networks defines sites of plasticity which shape animal behaviour.