The Functional Nano-Organization of Distinct Forms of Neurotransmission

Abstract

Within the single micron of the synapse action potential dependent and independent neurotransmission concurrently signal. However, the molecular mechanisms that mediate and regulate the specificity and diversity of this synaptic signaling is lacking. In this dissertation a synaptic nano-organization composed of neurotransmitter release machinery, molecular platforms, scaffolding proteins, and liquid complexes that support the discrete signaling of evoked and spontaneous neurotransmission are outlined. First, the use of the molecularly specific small molecule, Artemisinin, reveals the concentric post-synaptic center surround organization of evoked and spontaneous neurotransmission at GABAergic synapses. Subsequently, the pharmacological disruption of liquid-liquid phase separation uncovers how pre-synaptic active zone liquid condensates facilitate evoked release at both glutamatergic and GABAergic synapses at nanoscale. Lastly, chronic clinically relevant genetic manipulations provide mechanistic insight into rare developmental and epileptic encephalopathies, while simultaneously illuminating the dynamic relationship between SNARE mediated release machinery and the structure of the synapse in dually regulating basal neurotransmission. The described robust nano-organization supports unique functional roles for each discrete mode of release at both excitatory glutamatergic and inhibitory GABAergic synapses. This work proposes a fundamental design principle, that the single synapse is a highly ordered and compartmentalized unit whereby the functional nano-segregation of distinct forms of neurotransmission shapes synaptic efficacy. The elucidation of basic synaptic physiology is essential to both uncovering mechanisms underlying neurological diseases and designing their treatment.