Axin protein

XAV939 Regulates Axin Protein Levels by Inhibiting Tankyrases... 

Fig. 14.16 Schematic overview of the Wnt signaling pathway. Central to wnt signaling is a protein complex composed of/ -catenin, APC, glycogen synthase kinase 3 (CSK3) and axin.

Loss of A PC function leads to uncontrolled activation of the Wnt// -catenin pathway and provides a proliferative advantage to the mutated cell (reviews Moon et al., 2002 Fodde, 2003). In addition, chromosomal instability is observed in cells with decreased APC function. The C-terminus of APC encompasses domains responsible for proper attachment of the mitotic spindle to the kinetochore, and it is assumed that loss of this function elicits chromosomal instability. It is remarkable that two central aspects of tumor formation, namely proliferative advantage and chromosomal instability, are observed upon deactivation of the Wnt// -catenin pathway. Malfunction of other components of the Wnt/ -catenin pathway has also been observed in tumors. The scaffold protein axin has been... 

Ordinarily, the APC/Axin/GSK-3p multimeric protein complex maintains low levels of cytoplasmic 5-catenin within cells by binding to and phosphorylating free cytoplasmic P-catenin, which causes it to be degraded by the ubiquitin proteasome. However, when active Wnt signaling occurs, the APC/Axin/GSK-3p protein complex is prevented from binding to and phosphorylating cytosolic p-catenin, and this causes... 

The ctenophores operate a physiologically deviant Wnt pathway without axin, thus promoting P-catenin s intranuclear transfer further, the inhibitory dickkopf protein is also absent. These cells are physiologically functioning as if malignantly transformed , like colon cancer cells (see in the Appendix 1). 

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