The phosphoinositide-binding protein TRAF4 modulates tight junction stability and migration of cancer cells

Tumor necrosis factor (TNF) receptor-associated factor 4 (TRAF4), a protein localized in TJs in normal epithelial cells, is frequently overexpressed in carcinomas. We recently found that TRAF4 impedes TJ formation/stability and favors cell migration, 2 hallmarks of cancer progression. In addition TRAF4 contributes to the TGF-β-induced epithelial-mesenchymal transition (EMT), metastasis, and p53 destabilization. TRAF4 recruitment to TJs is a prerequisite for its biological function on TJ formation/stability and on cell migration. Interestingly, TRAF4 is targeted to TJs through lipid-binding. The trimeric TRAF domain of TRAF4 binds 3 phosphoinositide (PIP) molecules. These findings shed new light on the role of TRAF4 in cancer progression; they provide a novel link between lipid metabolism and cancer progression and support the notion that TRAF4 could be a relevant target for cancer therapies. TRAF4 belongs to a family of 7 human proteins involved in different biological processes, such as inflammation, immunity and embryonic development. While the lipid-binding ability of the TRAF domain is conserved among the whole TRAF protein family, its functional role remains to be established for the remaining TRAF proteins.