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XB-ART-43698
J Biol Chem 2010 Jul 30;28531:24120-30. doi: 10.1074/jbc.M110.113662.
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Complete functional segregation of planarian beta-catenin-1 and -2 in mediating Wnt signaling and cell adhesion.

Chai G , Ma C , Bao K , Zheng L , Wang X , Sun Z , Salò E , Adell T , Wu W .


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beta-Catenin is a bifunctional protein participating in both cell adhesion and canonical Wnt signaling. In cell adhesion, it bridges the transmembrane cadherin and the actin-binding protein alpha-catenin and is essential for adherens junction formation, whereas in canonical Wnt signaling, it shuttles between the cytosol and nucleus and functions as an essential transcriptional activator. Schmidtea mediterranea beta-catenin-1 was identified as a determinant of antero-posterior polarity during body regeneration by mediating Wnt signaling. Here we show that S. mediterranea beta-catenin-2 is specifically expressed in epithelial cells in the gut and pharynx, where it has a putative role in mediating cell adhesion. We show evidence that planarian beta-catenin-1 and -2 have distinct biochemical properties. beta-Catenin-1 can interact with the components of the canonical Wnt signaling pathway but not with alpha-catenin, whereas beta-catenin-2 interacts with cell adhesion molecules, including E-cadherin and alpha-catenin, but not with Wnt signaling components. Consistent with their specific function, beta-catenin-1 is a potent transcriptional activator, whereas beta-catenin-2 has no transcriptional activity. Protein sequence alignment also indicates that the planarian beta-catenin-1 and -2 retain distinct critical residues and motifs, which are in agreement with the differences in their biochemical properties. At last, phylogenetic analysis reveals a probable Platyhelminthes- specific structural and functional segregation from which the monofunctional beta-catenins evolved. Our results thus identify the first two monofunctional beta-catenins in metazoans.

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Species referenced: Xenopus
Genes referenced: actl6a cdh1

References [+] :
Adell, Smed-Evi/Wntless is required for beta-catenin-dependent and -independent processes during planarian regeneration. 2009, Pubmed