The regulated release of monoamines and neuropeptides from dense-core vesicles (DCVs) is essential for the modulation of metabolism, behavior, emotions, memory, and cognition. DCV biogenesis begins at the trans-Golgi network and culminates in docking at the cell membrane, but the precise mechanisms of DCV cargo sorting and maturation remain elusive. Additionally, some neurons have multiple kinds of DCVs carrying different cargos and that are released at distinct sites. As a model for learning how cells sort cargos to distinct DCVs, we are using the ASI sensory neurons that modulate nociceptive behavior in C. elegans. The ASI neurons express over 20 different peptides that localize to different parts of the cell, including the
nlp-9 and
nlp-18 neuropeptides which are trafficked mainly to the axon and the cell body, respectively. Prior work suggests that these two peptides are found in distinct DCVs that are released under different conditions. We crossed worms with GFP tagged
nlp-9 and
nlp-18 to worms with known mutants of DCV biogenesis such as
hid-1,
eipr-1,
rund-1, and
cccp-1, and found that the mutants had significantly decreased levels of
nlp-18 in the ASI cell body and axon compared to wildtype worms. This result is consistent with our previous observation that these mutants have decreased levels of another DCV cargo,
nlp-21, in the dorsal nerve cord. However, the levels of
nlp-9 in both the ASI cell body and axon remained largely unchanged in all the mutants compared to the wildtype, indicating that the sorting and maturation of
nlp-9 DCVs is not affected by the genes in our known pathway. This result suggests that a different pathway might be at play in the sorting and maturation of
nlp-9 DCVs.