Clarification of the interaction between the differentiation and immune regulation of goblet cells by Math1.

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Atoh1/Hath1 is indispensable to the differentiation of the intestinal epithelial cells, however what regulates Hath1 function has unknown. So we assessed the effect of Wnt signal for Hath1 and then, we revealed new signaling pathway for Hath1 in Wnt signals. The Hath-1 protein was actively degraded in SW480 cells where the Wnt signal is constitutively activated. In contrast, the breakdown of Hath-1 did not occur in 293T cells in which the Wnt signal remains inactivated. The degradation of Hath-1 in SW480 cells was inhibited by the treatment with MG132, an inhibitor for the proteasome, and the accumulated Hath-1 was shown to be ubiquitinated, indicating a role of ubiquitin-proteasome pathway in this process. Mutational analysis of Hath-1 showed that the critical residues regulating the proteolysis in SW480 cells are S54 and S58 that correspond to the consensus sequence for GSK-3 substrates. Indeed, pharmacological GSK-3 inhibitors blocked the Hath-1 degradation in SW480 cells. Importantly, the degradation of Hath-1 in SW480 cells was also inhibited by cotransfection of wt-APC, which reciprocally enhanced the degradation of β-catenin. Conversely, coexpression of Wnt1 in 293T cells resulted in the proteolysis of Hath-1, while it facilitated the accumulation of β-catenin.Next we demonstrated that the identification of genes directly targeted by Hath1. Several genes were selected by RNA micro array analysis or CHIP-on-chip analysis.We showed a novel branching of the Wnt-GSK-3 axis of signaling pathway, suggesting its important role in balancing the cellular differentiation and proliferation via the inverse regulation for the stability of Hath-1 and p-catenin proteins.