Analysis of the interactions between BP 180 , BP 230 , plectin and the integrin α 6 β 4 important for hemidesmosome assembly

Hemidesmosomes (HDs) are multi-protein complexes that promote epithelial-stromal cohesion in stratified and complex epithelia, and connect the intermediate filament system of basal epithelial cells to proteins of the extracellular matrix. These complexes, which ultrastructurally appear as tripartite structures along the plasma membrane of basal cells, are composed of at least five different proteins: the laminin-5 receptor α6β4, the bullous pemphigoid antigens 180 (BP180, BPAG2 or type XVII collagen) and 230 (BP230 or BPAG1-e), In certain tissues, such as intestinal epithelia, and cultured epithelial cells, a second type of HD has been identified, which is composed of α6β4 and plectin (Uematsu et al., 1994; Orian-Rousseau et al., 1996). These type II HDs, in contrast to the classical or type I HDs, do not exhibit the typical tripartite structure. BP230 and plectin are cytoplasmic proteins that belong to the plakin protein family, which also includes desmoplakin, envoplakin and periplakin. These proteins are crucially involved in the organization of the cytoskeleton (Ruhrberg and Watt, 1997; Leung et al., 2001). They are composed of domains that have considerable sequence homology. Their N-terminus consists of a plakin domain containing a number of subdomains of high α