Organization and Function of the Periactive Zone

PROJECT SUMMARY Membrane trafficking machinery plays pivotal roles in neuronal development, physiology, and neurological disorders. In particular, canonical endocytic proteins regulate diverse cell biological processes at synapses, including synaptic vesicle recycling, growth factor receptor traffic, synaptic adhesion, and neuropeptide secretion. At synapses much of this machinery accumulates at high concentrations in a specialized micron- scale membrane domain called the periactive zone (PAZ), suggesting the presence of synapse-specific organization and regulatory mechanisms. We do not understand how this structure is assembled, or how the synapse directs subsets of PAZ proteins to particular cell biological functions in space and time. The goal of this proposal is to identify new synapse-specific mechanisms that deploy the PAZ machinery to diverse cell biological processes to promote normal synapse development and function in vivo. To meet this goal, we propose to investigate the mechanisms that promote PAZ assembly and control its cell biological functions using two model systems in Drosophila – the larval neuromuscular junction and neurons regulating the circadian clock. In these studies, we will combine cutting edge live and super-resolution imaging, image analysis, and mechanistic separation-of-function perturbations to understand PAZ regulation and function at molecular, cellular, and behavioral scales. We will extend our mechanistic insights from the neuromuscular junction into the central nervous system to determine how PAZ cell biological functions control the development and function of circadian pacemaker neurons in vivo. Aim 1 will characterize how the PAZ assembles during developmental, activity-induced, and circadian synapse formation, and identify how synaptic adhesion molecules regulate PAZ assembly and organization. Aim 2 will determine how combinations of PAZ proteins regulate neuropeptide secretion by controlling where, when, and how dense core vesicles dock and fuse at the synapse. These investigations will inject fresh mechanistic insights into synapse-specific control of the membrane trafficking machinery, and we expect that understanding these basic mechanisms will illuminate specific, targetable links between these conserved proteins and diverse neurological and neurodegenerative disorders.