Hemidesmosomes are adhesion complexes responsible for linking keratin
intermediate filaments of stratified and complex epithelia to componen
ts of the extracellular matrix such as collagen fibrils. Over the past
several years, it has become clear that there are at least five hemid
esmosomal proteins, including HD1/plectin and BP230 as cytoplasmic pla
que proteins and integrin alpha 6 beta 4 and BP180 as transmembrane pr
oteins. Among them, BP180 is unique as a transmembrane protein because
of its collagenous extracellular domain. Recent biochemical and ultra
structural analyses have revealed its molecular configuration and natu
re as a major component of anchoring filaments connecting hemidesmosom
es to the basement membrane. These results indicate that BP180 is a ne
w type of adhesion receptor. In addition to biochemical analyses of th
ese hemidesmosomal proteins, recent studies on patients with inherited
skin blistering diseases and on knockout mice have demonstrated roles
in hemidesmosome formation and stabilization, as well as unexpected,
novel functions. (C) 1998 Wiley-Liss. Inc.