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The Journal of Cell Biology, Vol. 176, No. 3, January 29, 2007 343353
Tight junctions, adherens junctions (AJs), and desmosomes
promote adhesion between epithelial cells, initiate the assembly
of the mechanical cytoskeleton linkage, and facilitate the for-
mation of a polarized epithelial monolayer (Gumbiner, 1996).
AJs initiate these processes and are essential for morphogene-
sis, wound healing, and the retention of cell polarity and tissue
integrity (Perez-Moreno et al., 2003). In epithelia, AJ formation
is mediated by the calcium-dependent homophilic binding of
E-cadherin molecules on neighboring cells (Gumbiner, 1996).
These interactions link adjacent cells and promote the nucle-
ation of a cytoplasmic protein complex consisting of p120-, -,
and -catenins, which bridges E-cadherin clusters and the actin
cytoskeleton. The biological necessity of AJ proteins has been