Mapping neuropeptide synthesis and trafficking in motor neurons

Abstract

Neuropeptides (NPs) are one of the most diverse forms of signaling molecules. NPs modulate countless cellular processes determining their fate, survival, and overall function. The impact of NP release on target cells varies tremendously, excitatory vs inhibitory, fast vs slow acting, ion channel vs GPCR. Given both the diversity of NPs in the genome, and their effects on target cells, uncovering the mechanisms of NP packaging, sorting, trafficking, and release is critically important. This is accentuated by mutations/defects in NP signaling that are associated with some of society’s most severe and debilitating diseases including neurodegenerative diseases, obesity, diabetes, and cancers. In this thesis, I am to uncover whether dense core vesicle (DCV) protein machinery is heterogeneous and cargo-specific. To test this, we initially screened 30 different motor proteins to assess their impacts on NP trafficking and aggregation within the Drosophila larval nervous system. Live imaging of fluorescently tagged NPs revealed two kinesins, kinesin 1 and 3, played critical roles in NP trafficking. I went on to examine the downstream implications of disrupted kinesin activity by examining changes in NMJ morphology. To uncover whether heterogeneity in DCV composition is cargo-specific, I first conducted immunohistochemical staining to visualize DCVs as they migrate through the sorting and packing pathways in the soma. These findings provide novel insights into NP transport mechanisms, highlighting the roles of specific motor proteins and expanding the toolkit for studying NP synthesis and trafficking.