REDISTRIBUTION OF THE HEMIDESMOSOME COMPONENTS ALPHA-6-BETA-4 INTEGRIN AND BULLOUS PEMPHIGOID ANTIGENS DURING EPITHELIAL WOUND-HEALING

As basal cells of stratified squamous epithelia become migratory in response to wounding, they lose their cell-substrate adhesion junctions, the hemidesmosomes. We report here studies to determine the fate of the hemidesmosome components, α6β4 integrin and the bullous pemphigoid antigens (BPAGs), as recognized by bullous pemphigoid autoantisera (BPA), in migrating epithelium. In addition, we report studies to determine whether relative synthesis and amount of α6β4 is altered during migration. Mouse corneas with 1.5- to 2-mm-diameter central epithelial debridements were allowed to heal in vitro or in vivo for 1-18 h. In order to do preembedding immunoelectron microscopic localization of of α6β4, sheets of stationary and migrating corneal epithelium were removed from their basal laminae after organ culture. BPA and antibodies to α6 and β4 were used for immunofluorescence microscopy on frozen sections of intact corneas healing in vivo 1-18 h. Both α6 and β4 were found to redistribute from their clustered location within hemidesmosomes to a more even distribution within the substrate-associated membrane of basal cells of the tip of the leading edge of migrating epithelium. Behind the tip of the leading edge, basal cells bound the integrin antibodies around their entire membrane. BPAGs moved from their location along the basal cell membrane of stationary epithelium to a diffuse location within the cytoplasm of migrating cells at the leading edge of migration. Quantitative immunoprecipitation and immunoblotting of α6β4 as well as β1 integrin from stationary and migrating epithelium were done to determine whether the synthesis or total amount of the integrins were altered during migration. The relative syntheses of α6β4 and β1 per milligram of protein or per cell do not appear to differ between stationary and migrating epithelium and the total amount of the β4 and β1 does not change despite increased rates of protein synthesis in migrating epithelium. Taken together, these studies suggest that as hemidesmosomes disassemble, their clustered integrin component distributes more evenly in the basal cell membrane, the components recognized by BPA and associated with intermediate filaments are released from the membrane, and these events occur in the absence of any measurable change in the synthesis or total amount of the α6β4 component. © 1993 Academic Press, Inc.