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Review
Re-Evaluating the Role of Frat in Wnt-Signal Transduction
Renée van Amerongen and Anton Berns
volume 4 | issue 8
august 2005Pages: 1065-1072
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Frat proteins are potent activators of canonical Wnt-signal transduction. By binding to GSK3, Frat prevents the phosphorylation and concomitant degradation of ?-catenin and allows the activation of downstream target genes by ?-catenin/TCF complexes. The identification of the Xenopus Frat homologue GBP as an essential component of the maternal Wnt-pathway during embryonic axis formation suggested that Frat might fulfill a similar role in higher vertebrates. As a result most, if not all, studies addressing Frat function have focused on its ability to bind GSK3 and induce signaling through ?-catenin/TCF. Consequently, Frat has been advocated as the “missing link” that bridged signaling from Dishevelled to GSK3 in the canonical Wnt-pathway. Recent mouse-knockout studies however, call for a re-evaluation of the physiological role of Frat. Mice that lack all Frat-family members appear to be normal and display no obvious defects in ?-catenin/TCF signaling. This observation re-opens the question as to how GSK3 activity is controlled in vertebrate canonical Wnt-signal transduction in view of the apparent dispensability of Frat. Here we will review the studies that have been conducted on Frat proteins to date, with a specific focus on those that implicate a role for Frat in Wnt-signal transduction. In addition, we will discuss potential alternatives for the endogenous function of Frat.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.