Advances and perspectives of the architecture of hemidesmosomes: Lessons from structural biology

Abstract

Hemidesmosomes (HD) are adhesive protein complexes that mediate stable attachment of basal epithelial cells to the underlying basement membrane. The organization of HDs relies on a complex network of protein-protein interactions, in which integrin α6β4 and plectin play an essential role. Here we summarize the current knowledge of the structure of hemidesmosomal proteins, which includes the structures of the first and second fibronectin type III (FnIII) domains and the calx-β domain of the integrin β4 subunit, the actin binding domain of plectin, and two non-overlapping pairs of spectrin repeats of plectin and BPAG1e. Binding of plectin to the β4 subunit is critical for the formation and the stability of HDs. The recent 3D structure of the primary complex between the integrin β4 subunit and plectin has provided a first insight into the macromolecular recognition mechanisms responsible for HD assembly. Two missense mutations in β4 linked to non lethal forms of epidermolysis bullosa map on the plectin-binding surface. Finally, the formation of the β4-plectin complex induces conformational changes in β4 and plectin, suggesting that their interaction may be subject to allosteric regulation. ©2009 Landes Bioscience.