Catenins

Kemler, R. (1993). From cadherins to catenins Cytoplasmic protein mreracrions and reglnrion of cell adhesion. Trends Genet. 9(9), 317-321. 

Cadherins (Calcium-dependent adhesion proteins) are transmembrane proteins, which consist of an extracellular domain composed of cadherin-repeats, a transmembrane domain, and a cytoplasmic domain that interacts with catenins and/or other cytoplasmic proteins. 

Catenins are defined as cytoplasmic interaction partners of cadherins that form a chain of proteins ( catena, latin for chain), which connects cadherins to the actin cytoskeleton. 

Several nonconventional cadherins that contain cadherin repeats have been described but they have specific features not found in the classical cadherins [1]. The cadherin Flamingo, originally detected in Drosophila, contains seven transmembrane segments and in this respect resembles G protein-coupled receptors. The extracellular domain of Flamingo and its mammalian homologs is composed of cadherin repeats as well as EGF-like and laminin motifs. The seven transmembrane span cadherins have a role in homotypic cell interactions and in the establishment of cell polarity. The FAT-related cadherins are characterized by a large number of cadherin repeats (34 in FAT and 27 in dachsous). Their cytoplasmic domains can bind to catenins. T- (=truncated-)cadherin differs from other cadherins in that it has no transmembrane domain but is attached to the cell membrane via a glycosylpho-sphatidylinositol anchor. 

The cytoplasmic domains of protocadherins are unrelated to those of classical cadherins. They do not bind catenins and it is not clear whether they are associated with the cytoskeleton [1]. Some protocadherins interact with the c- src-related kinase Fyn, indicating a role in signal transduction (see below). 

Classical and desmosomal cadherins are constituents of different types of intercellular junctions. E-cadherin, the classical cadherin of epithelial cells, is part of the adherens junction (zonula adherens), which is attached to a belt of actin via the catenins. As the name says, desmosomal cadherins are part of the desmosomes, which are rivet-like structures that make focal connections between cells. Desmosomes are characterized by a... 

Stein U, Arlt F, Walther W et al (2006) The metastasis-associated gene S100A4 is a novel target of p-catenin/ T-cell factor signaling in colon cancer. Gastroenterology 131 1486-1500... 

It has been proposed that the vertebrate Wnt genes can be classified based on whether they activate (3-catenin-dependent or non- 3-catenin signaling pathways (see below). However, the response to a Wnt of one proposed class can be switched to that of the other class by coexpressing a specific Wnt receptor. 

Adenomatosis Polyposis Coli (APC). Whereas Dvl is a Wnt pathway activator, GSK3, Axin and APC are all inhibitors. Axin and APC help to stabilize the activity of GSK3, keeping (3-catenin levels low and Wnt target gene transcription off in the absence of a Wnt signal (Fig. 2a). 

Besides the well-established Wnt/(3-catenin-dependent pathway components mentioned above, several additional cytoplasmic inhibitors of Wnt/ 3-catenin-dependent signaling have been identified that share... 

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