Catenin

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Catenins are proteins found in complexes with cadherin cell adhesion molecules of animal cells. The first two catenins that were identified^[2] became known as alpha-catenin and beta-catenin. Alpha-catenin can bind to beta-catenin and can also bind actin. Beta-catenin binds the cytoplasmic domain of some cadherins. Additional catenins such as gamma-catenin and delta-catenin have been identified. The name "catenin" was originally selected ('catena' means 'chain' in Latin) because it was suspected that catenins might link cadherins to the cytoskeleton.^[3]

Types

• alpha catenin

• beta catenin

• delta catenin

• gamma catenin

All but alpha contain armadillo repeats.

Catenins and cadherin function

F9 embryonal carcinoma cells are similar to the P19 cells shown in Figure 1 and normally have cell-to-cell adhesion mediated by E-cadherin with beta-catenin bound to the cytoplasmic domain of E-cadherin. F9 cells were genetically engineered to lack beta-catenin, resulting in increased association of plakoglobin with E-cadherin.^[4] In F9 cells lacking both beta-catenin and plakoglobin, very little E-cadherin and alpha-catenin accumulated at the cell surface.^[4] Mice lacking beta-catenin have defective embryos. Mice engineered to specifically have vascular endothelium cells deficient in beta-catenin showed disrupted adhesion between vascular endothelial cells.^[5] Mice lacking plakoglobin have cell adhesion defects in many tissues, although beta-catenin substitutes for plakoglobin at many cellular junctions.^[6] Keratinocytes engineered to not express alpha-catenin have disrupted cell adhesion^[7] and activated NF-kB.^[8] A tumor cell line with defective delta-catenin, low levels of E-cadherin and poor cell-to-cell adhesion could be reverted to normal epithelial morphology and increased E-cadherin levels by expression of normal levels of functional delta-catenin.^[7]

References