b-Catenin is a cytoplasmic phosphoprotein under resting conditions. The cellular localization of b-Catenin is regulated through its phosphorylation.by GSK-3, which lies upstream. In the absence of wnt signal b-Catenin is phosphorylated by GSK-3 and targeted for degradation by the ubiquitin-proteasome system. Upon wnt signaling it can not be phosphorylated by GSK3 resulting in the its cytoplasmic accumulation and translocation to the nucleus. In the nucleus, it can interact with transcription factors and control the transcriptional activation of the genes. b-catenin can bind to cadherins, the tumor suppressor gene product Adenomatous Polyposis Coli (APC), lymphocyte enhancer-binding factor (LEF) and T-cell factor. The Drosophila homologue, Armadillo, has an N-terminal acidic region, 13 central copies of a 42 amino acid repeat (called as armadillo repeat: mediates protein interactions), and a C-terminal glycine proline rich region. These regions show varying degree of homology to human Plakoglobin.
b-Catenin is an important regulator of cellcell adhesion and embryogenesis and there is evidence that mutations of b-catenin could lead to some human cancers.
Gumbiner, B. (1997) Signal transduction by ß-catenin. Curr. Opin. Cell Biol. 7:634-640.
Keith Orforda, Caroline C. Orforda, and Stephen W. Byersa. 1999. Exogenous Expression of ß-Catenin Regulates Contact Inhibition, Anchorage-independent Growth, Anoikis, and Radiation-induced Cell Cycle Arrest. J. Cell Biol., 146 (4), 855-868
Kitagawa M, Hatakeyama S, Shirane M, Matsumoto M, Ishida N, Hattori K, Nakamichi I, Kikuchi A, Nakayama K, Nakayama K. 1999. An F-box protein, FWD1, mediates ubiquitin-dependent proteolysis of beta-catenin. EMBO J 18(9):2401-10
Peifer, M. (1995) Cell adhesion and signal transduction: the Armadillo connection. Trends Cell Biol 5:224-229.
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