ABSTRACT:
Lee2003 - Roles of APC and Axin in Wnt
Pathway (without regulatory loop)
This model is described in the article:
The roles of APC and Axin
derived from experimental and theoretical analysis of the Wnt
pathway.
Lee E, Salic A, Krüger R,
Heinrich R, Kirschner MW.
PLoS Biol. 2003 Oct; 1(1): E10
Abstract:
Wnt signaling plays an important role in both oncogenesis
and development. Activation of the Wnt pathway results in
stabilization of the transcriptional coactivator beta-catenin.
Recent studies have demonstrated that axin, which coordinates
beta-catenin degradation, is itself degraded. Although the key
molecules required for transducing a Wnt signal have been
identified, a quantitative understanding of this pathway has
been lacking. We have developed a mathematical model for the
canonical Wnt pathway that describes the interactions among the
core components: Wnt, Frizzled, Dishevelled, GSK3beta, APC,
axin, beta-catenin, and TCF. Using a system of differential
equations, the model incorporates the kinetics of
protein-protein interactions, protein synthesis/degradation,
and phosphorylation/dephosphorylation. We initially defined a
reference state of kinetic, thermodynamic, and flux data from
experiments using Xenopus extracts. Predictions based on the
analysis of the reference state were used iteratively to
develop a more refined model from which we analyzed the effects
of prolonged and transient Wnt stimulation on beta-catenin and
axin turnover. We predict several unusual features of the Wnt
pathway, some of which we tested experimentally. An insight
from our model, which we confirmed experimentally, is that the
two scaffold proteins axin and APC promote the formation of
degradation complexes in very different ways. We can also
explain the importance of axin degradation in amplifying and
sharpening the Wnt signal, and we show that the dependence of
axin degradation on APC is an essential part of an
unappreciated regulatory loop that prevents the accumulation of
beta-catenin at decreased APC concentrations. By applying
control analysis to our mathematical model, we demonstrate the
modular design, sensitivity, and robustness of the Wnt pathway
and derive an explicit expression for tumor suppression and
oncogenicity.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000658.
To cite BioModels Database, please use:
Chelliah V et al. BioModels: ten-year
anniversary. Nucl. Acids Res. 2015, 43(Database
issue):D542-8.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Emma Fairbanks 
