Structural and functional investigations on synaptic vesicular transporters

PROJECT SUMMARY Chemical neurotransmission, an essential component of neuronal communication in the brain, is facilitated by specialized organelles known as synaptic vesicles. These vesicles mediate the release of neurotransmitters across synapses. Transporters within the vesicles establish chemical and electrical gradients and load neurotransmitters into the vesicles, ensuring efficient neurotransmitter release. Defects in these transporters often associate with neurological diseases, including epilepsy, neurodegeneration, and mental illness. Despite their importance, many of these transporters remain understudied at a molecular level. One of the most abundant membrane proteins in synaptic vesicles is synaptic vesicle glycoprotein 2 (SV2), a putative transporter that is critical for normal synaptic function. Mutations in human SV2 lead to epilepsy and cognitive impairment, and SV2 is a known target of commonly used antiepileptic medications. However, the precise function of SV2 and how it mediates synaptic transmission remain largely unknown. Similarly, the mechanism by which drugs targeting SV2 treat epilepsy is still elusive. We propose an integrated approach that combines single-particle cryo-electron microscopy, in vivo and in vitro assays, and mass spectrometry to answer critical questions about SV2: what is its substrate and how is it recognized? What is the nature of the translocation pathway and how does SV2 transport the substrate? How do antiepileptic drugs regulate SV2? Our research will significantly advance our understanding of the function and mechanisms of SV2 in synaptic biology, and provide a strong foundation for developing more effective therapeutic interventions for epilepsy.