Translocation of β-catenin into the nucleus independent of interactions with FG-rich nucleoporins

Abstract

β-Catenin nuclear import has been found to be independent of classical nuclear localization signal (NLS) nuclear import factors. Here, we test the hypothesis that β-catenin interacts directly with nuclear pore proteins to mediate its own transport. We show that β-catenin, unlike importin-β, does not interact detectably with Phe/Gly(FG)-repeat-rich nuclear pore proteins or nucleoporins (Nups). Moreover, unlike NLS-containing proteins, β-catenin nuclear import is not inhibited by wheat germ agglutinin (WGA) or excess importin-β. These results suggest β-catenin nuclear translocation does not involve direct interactions with FG-Nups. However, β-catenin has two regions that can target it to the nucleus, and its import is cold sensitive, indicating that β-catenin nuclear import is still an active process. Transport is blocked by a soluble form of the C-cadherin cytoplasmic domain, suggesting that masking of the nuclear targeting signal may be a mechanism of regulating β-catenin subcellular localization.