Cell polarity is critical for the function of the many cell types. In C. elegans, basolateral localization of the LET-23 Epidermal Growth Factor Receptor (EGFR) in the vulval precursor cells (VPCs) is required for the development of the vulva. A class I/II Arf GTPase pathway regulated by AGEF-1, a homolog of the mammalian BIG1/2 Arf GEFs, antagonizes LET-23 EGFR signaling by promoting its apical trafficking. Loss of the AGEF-1/Arf GTPase/AP-1 pathway results in increased basolateral LET-23 EGFR and over induction of vulva tissue. Thus, this pathway is required to maintain the proper levels of LET-23 EGFR at the basolateral membrane to ensure proper vulva induction. In human, the EGFR signaling pathway is frequently over-activated in many cancers and studying the mechanisms regulating EGFR signaling is crucial to understand the development of EGFR-related diseases. We found that RAB-10 GTPase has novel antagonistic interactions with the Arf GTPase pathway. RAB-10 GTPase is required for
agef-1(
vh4) trafficking phenotypes in several tissues including increased basolateral localization of LET-23 EGFR in the VPCs, but it is not required for LET-23 EGFR localization in a wild-type background. RAB-10, AGEF-1 as well as the Arf GTPase pathway localize to Golgi and recycling endosomes to regulate polarized trafficking in epithelial cells, however, it is not known how their functions are coordinated. The focus of my project is to find how RAB-10 interacts with the Arf GTPase pathway and which effectors and regulators function with RAB-10 to regulate LET-23 EGFR localization and signaling. Our genetic epistasis indicates that
rab-10(+) is required downstream of
agef-1(
vh4) and
arf-1(
ok796), but upstream or in parallel with
unc-101(
sy101) AP-1 m subunit. Thus, RAB-10 might function with the AP-1 clathrin adaptor complex in the absence of Arf GTPase activity to promote basolateral transport of LET-23 EGFR. Additionally, we screened RAB-10 effectors for interactions with the AGEF-1. Two RAB-10 effectors, CNT-1, an Arf6 GAP, and SEC-15, a subunit of the exocyst complex, are suppressors of
agef-1(
vh4) embryonic phenotypes. Unexpectedly, we found that CNT-1 functions opposite of RAB-10 in the VPCs and thus might function in a distinct pathway. We are still testing the role of SEC-15 in regulation of LET-23 EGFR trafficking. These studies will determine how RAB-10 and the AGEF-1/Arf/AP-1 trafficking intersects to regulate polarized transport in epithelial cells.