Drosophila Twins regulates Armadillo levels in response to Wg/ Wnt signal.
Protein Phosphatase 2A ( PP2A) has a heterotrimeric-subunit structure, consisting of a core dimer of approximately 36 kDa catalytic and approximately 65 kDa scaffold subunits complexed to a third variable regulatory subunit. Several studies have implicated PP2A in Wg/ Wnt signaling. However, reports on the precise nature of PP2A role in Wg/ Wnt pathway in different organisms are conflicting. We show that twins (tws), which codes for the B/PR55 regulatory subunit of PP2A in Drosophila, is a positive regulator of Wg/ Wnt signaling. In tws(-) wing discs both short- and long-range targets of Wingless morphogen are downregulated. Analyses of tws(-) mitotic clones suggest that requirement of Tws in Wingless pathway is cell-autonomous. Epistatic genetic studies indicate that Tws functions downstream of Dishevelled and upstream of Sgg and Armadillo. Our results suggest that Tws is required for the stabilization of Armadillo/beta-catenin in response to Wg/ Wnt signaling. Interestingly, overexpression of, otherwise normal, Tws protein induce dominant-negative phenotypes. The conflicting reports on the role of PP2A in Wg/ Wnt signaling could be due to the dominant-negative effect caused by the overexpression of one of the subunits.[1]References
- Drosophila Twins regulates Armadillo levels in response to Wg/Wnt signal. Bajpai, R., Makhijani, K., Rao, P.R., Shashidhara, L.S. Development (2004) [Pubmed]
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