ALPHA-6-BETA-4 INTEGRIN HETERODIMER IS A COMPONENT OF HEMIDESMOSOMES

Antisera that recognize the α6 and β4 subunits of integrins were found by immunoelectron microscopy to localize to hemidesmosomes in the basal cells of mouse corneal epithelium. Immunoprecipitation experiments using extracts of metabolically labeled corneal epithelial cells indicate that the primary α6-subunit-containing integrin heterodimer present is α6β4 and not α6β1. Here we extend previous studies to report that by immunofluorescence microscopy the α6 integrin subunit colocalizes with bullous pemphigoid antigen and type VII collagen in newly forming hemidesmosomes in the developing 17-day fetal rabbit eye. Neither the composition of the anchoring filaments, which span the region between the hemidesmosomal plaque and the lamina densa of basement membrane where the globular domain of type VII collagen is located, nor the extracellular ligand of α6β4 is known. Once anchoring filament proteins are identified, it will be of interest to determine whether any bind to α6β4.