Axin-induced apoptosis depends on the extent of its JNK activation and its ability to down-regulate β-catenin levels

Abstract

Axin is a multidomain protein that coordinates a variety of critical factors in Wnt signaling and JNK activation. In this study, we found that overexpression of Axin leads to apoptosis in several cell lines. A mutant Axin (Axin-ΔMID) that does not contain the MEKK1-interacting domain and is not capable of activating JNK, has less apoptotic effect. Together with the observations that dominant-negative forms of MEKK1 and JNK1 can attenuate Axin-induced apoptosis, we suggest that JNK activation is required for Axin-mediated apoptosis. Wild-type Axin proteins that can lead to destabilization of β-catenin are more effective at causing cell death than those constructs (Axin-ΔGSK/β-cat, Axin-ΔRGS/GSK/β-cat) that are defective in regulation of β-catenin but still fully capable of JNK activation. Furthermore, enhanced β-catenin signaling by coexpression of β-catenin or PP2Cα attenuate cell death. Taken together, we suggest that the ability of Axin to induce apoptosis is determined by its ability to activate JNK and destabilize β-catenin. (C) 2000 Academic Press.