DIO3 associates with sorting nexins and endosomal trafficking networks in ovarian cancer

Puropose: Type 3 iodothyronine deiodinase (DIO3) is a membrane-associated enzyme that inactivates thyroid hormones and promotes high-grade serous ovarian cancer (HGSOC) progression. Although DIO3 undergoes continuous recycling between the plasma membrane and endosomal compartments, the mechanisms governing its intracellular routing and functional stability remain unknown. Methods: We used Human ovarian cancer cells (ES-2, OVCAR3, OVSAHO, KURAMOCHI, NCI/ADR (NAR)), ovarian cancer tumors and normal tissues from patients, immortalized fallopian tube cells (FT109, FT237 and FT282) and HEK293T cells. DIO3 was knocked-down (shRNA) or overexpressed (CRISPR activation system). Flow cytometry (cell counts and apoptosis assay), proteomics, co-immunoprecipitation, proximity ligation assay, confocal imaging in the presence of endosomal transport inhibitors, and AlphaFold-based structural modeling were performed. Results: We identify sorting nexins SNX2 and SNX6 as components of the DIO3 trafficking machinery in ovarian cancer. Computer-based structural analysis provide a potential interface for SNXs association, requiring intact linker and catalytic domains of DIO3. Studies in ovarian cancer cells suggest that SNX6 is linked with DIO3 progression through endosomal and Golgi compartments, whereas SNX2 is associated with its recycling to the plasma membrane via RAB11-positive vesicles. Disruption of these pathways destabilizes DIO3-SNXs colocalization and selectively impairs proliferation and survival of DIO3-overexpressing cells. Conclusion: These findings establish intracellular trafficking as a fundamental determinant of DIO3 stability and function and uncover sorting nexin-associated routing as a previously unrecognized dependency and therapeutic vulnerability in ovarian cancer cells.