The spatial organization of signal transduction cascades is critical for regulating cell signalling and function. This is particularly evident in the polarized epithelia of Caenorhabditis elegans vulva precursor cells (VPCs) that give rise to the hermaphrodite vulva. Epidermal Growth Factor Receptor (LET-23 EGFR) signalling from the basolateral membrane is required for vulva cell fate induction. Basolateral localization of LET-23 EGFR is dependent on a ternary complex composed of LIN-2 CASK, LIN-7 Veli, and LIN-10 Mint1. Disruption of this complex results in exclusive apical mislocalization of LET-23 and a vulvaless (Vul) phenotype. This complex has been well-defined biochemically, however the cellular mechanisms by which it regulates LET-23 localization are not understood. We previously identified a pathway consisting of ARF GTPases, AGEF-1 (a putative Arf guanine exchange factor), and the AP-1 clathrin adaptor complex that antagonizes basolateral localization of LET-23 and negatively regulates signalling. Interestingly, mammalian LIN-10 homologue Mint1 binds Arf GTPases and may serve as an adaptor protein analogous to the AP-1 complex. My primary research objective is to discover how the LIN-2/7/10 complex functions with the AGEF-1/ARF/AP-1 ensemble to regulate LET-23 trafficking and signalling in the C. elegans VPCs. I found that GFP::LIN-10 localizes to cytoplasmic foci in the VPCs, which may represent Golgi mini-stacks or recycling endosomes. This localization is independent of LIN-2, LIN-7, and ARF GTPases, and is mediated by the C-terminal PTB and PDZ domains of LIN-10 that also mediate Arf binding in mammalian Mint1. Unexpectedly, I found that overexpression of LIN-10 rescues the lin-2(e1309) and lin-7(e1413) Vul phenotypes, indicating that LIN-10 promotes signalling independently of its complex. This effect is mediated by the C-terminal domains of LIN-10, and is LET-23 dependent. Going forward, I will test the hypothesis that LIN-10 promotes the EGFR signalling pathway by interacting with ARF. I will find if LIN-10 and ARF colocalize and interact in C. elegans, and I will test if this interaction is necessary and sufficient for the rescue of the lin-2(e1309) and lin-7(e1413) Vul phenotypes. Also, I will test if overexpression of LIN-10 can affect the subcellular localization of LET-23::GFP in the VPCs. This will be crucial towards understanding how LIN-10 overexpression is able to rescue the lin-2(e1309) and lin-7(e1413) Vul phenotypes. The results will offer new insight into how trafficking and scaffolding components work together to carefully regulate cellular events by controlling the spatial organization of signalling proteins in polarized cells.