Expression of β4 Integrins in Human Skin: Comparison of Epidermal Distribution with β1-Integrin Epitopes, and Modulation by Calcium and Vitamin D3 in Cultured Keratinocytes

Abstract

The expression of beta 4 integrins in adult and fetal human skin as well as in cultured keratinocytes was studied by immunodetection with monoclonal antibodies, and compared with that of beta 1 integrins. The distribution of the beta 1 and beta 4 integrin epitopes was entirely different in the adult epidermis. As reported previously by us (J Clin Invest 84:1916, 1989), the beta 1 epitopes were present most prominently at lateral cell-cell contact points, whereas staining with the beta 4 antibody demonstrated a linear staining pattern polarizing to the basal surface juxtaposed to the dermal-epidermal basement membrane. In contrast, in fetal skin, the staining patterns both with beta 1 and beta 4 antibodies were similar and demonstrated the presence of epitopes surrounding the entire cell surface of both basal and suprabasal keratinocytes. Distinct polarization of beta 4 integrin epitopes was noted in cultured keratinocytes maintained in low-calcium (0.15 mM) medium, and the expression of these integrins was also noted in human papilloma virus-transformed keratinocytes. Switch of the cultures to high-calcium (1.2 mM) medium resulted in redistribution of the epitopes to a pattern suggesting their location at under-surface of the cells adjacent to the substratum. This Ca(++)-induced redistribution of beta 4 integrin epitopes could be counteracted by 10(-7) M vitamin D3. Finally, incubation with anti-beta 4 integrin antibody reduced the capacity of keratinocytes to attach to plastic substratum. The results provide further evidence for the role of beta 4 integrins in cell-matrix interactions.