884A Poster - 14. Neural circuits and behavior
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Emily Hendricks; Faith Liebl

Affiliation: Southern Illinois University Edwardsville

Keywords:
e. synaptic function and organization; w. other (Vesicle trafficking)

Tetraspanins are a well-conserved class of transmembrane proteins that play a regulatory role at the cell membrane by mediating the spatiotemporal distribution of their binding partners—often receptors, cell adhesion molecules, and intracellular signaling proteins. The tetraspanin, CD63, is a classical marker of exosomes and late endosomes and likely regulates vesicular traffic through the exocytic pathway. However, CD63’s role in mediating endocytic and exocytic dynamics at the synapse is not well described. Thus, we aim to use the Drosophila neuromuscular junction (NMJ) to characterize the role of CD63 orthologs, Tsp42Ee and Tsp42Eg, in regulating synaptic vesicle dynamics. We find that CD63-related tetraspanins negatively regulate endocytosis, likely through control of synaptic vesicle pool dynamics and localization of the synaptic proteins, Endophilin A and Dynamin. We also find that Tsp42Ee and Tsp42Eg regulate synaptic morphology and function as both tsp mutants show reductions in locomotor function and mEJC frequency. Furthermore, tsp42Eg loss of function mutants show reduction in quantal content and eEJC amplitude suggesting an overall reduction in synaptic vesicle release. These alterations in synaptic function may, at least in part, be attributed to disruptions in cytoskeletal structure as we observe an increase in Futsch loops at tsp mutant synapses. Together, these findings implicate CD63-related tetraspanins as overarching regulators of NMJ structure and synaptic vesicle pool dynamics. We will further explore this work by attempting to rescue the tsp mutant phenotype through expression of human CD63 in the tsp mutant backgrounds. These experiments will aim to validate the functional redundancy of hCD63 in Drosophila and further clarify the role that tetraspanins play at the synapse.