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Mol. Cell. Biol., 05 1996, 2128-2134, Vol 16, No. 5
J Papkoff, B Rubinfeld, B Schryver and P Polakis
The Wnt-1 proto-oncogene induces the accumulation of beta-catenin and
plakoglobin, two related proteins that associate with and functionally
modulate the cadherin cell adhesion proteins. Here we have investigated the
effects of Wnt-1 expression on the tumor suppressor protein APC, which also
associates with catenins. Expression of Wnt-1 in two different cell lines
greatly increased the stability of APC-catenin complexes. The steady-state
levels of both catenins and APC were elevated by Wnt-1, and the half-lives
of both beta-catenin and plakoglobin associated with APC were also markedly
increased. The stabilization of catenins by Wnt-1 was primarily the result
of a selective increase in the amount of uncomplexed, monomeric
beta-catenin and plakoglobin, detected both by affinity precipitation and
size- exclusion chromatography of cell extracts. Exogenous expression of
beta- catenin was possible in cells already responding to Wnt-1 but not in
the parental cells, suggesting that Wnt-1 inhibits an essential regulatory
mechanism for beta-catenin turnover. APC has the capacity to oppose this
Wnt-1 effect in experiments in which overexpression of the central region
of APC significantly reduced the size of the monomeric pool of beta-catenin
induced by Wnt-1. Thus, the Wnt-1 signal transduction pathway leads to the
accumulation of monomeric catenins and stabilization of catenin complex
formation with both APC and cadherins.
Copyright © 1996, American Society for Microbiology
Wnt-1 regulates free pools of catenins and stabilizes APC-catenin complexes
SUGEN, Inc., Redwood City, California 94063, USA.
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