Localization of ladsin, a homolog of laminin-5, in normal adult human tissues: immunohistochemical and immunoelectron microscopic studies.

Ladsin, a homolog of laminin-5, is a large cell-adhesive protein with potent cell-scattering activity. In the present study, we investigated, by immunohistochemistry, the distribution of ladsin in a wide range of normal adult human epithelial tissues along with that of integrin subunit α3 as a marker of integrin α3β1, which is the primary receptor of ladsin. Our results demonstrated that ladsin was localized in the basement membranes of almost all the epithelial tissues with coexisting integrin subunit α3 along the cell membranes, suggesting that their interaction is important in the maintenance of normal architecture and function of these membranes. Only cytoplasmic localization of ladsin was observed in the fundic glands, hepatocytes, renal tubuli, and acini of the mammary glands, and in these tissues, integrin subunit α3 was also localized in the cytoplasm. Both ladsin and integrin subunit α3 were absent in the acini of the pancreas, major salivary glands, and bronchial glands. These tissue- and cell type-specific localizations of ladsin and integrin subunit α3 likely reflect the differences in their role and function in each tissue.