Integrin α3-subunit expression modulates alveolar epithelial cell monolayer formation

Abstract

We investigated expression of the α3-integrin subunit by rat alveolar epithelial cells (AECs) grown in primary culture as well as the effects of monoclonal antibodies with blocking activity against the α3-integrin subunit on AEC monolayer formation. α3-Integrin subunit mRNA and protein were detectable in AECs on day 1 and increased with time in culture. α3- and β1-integrin subunits coprecipitated in immunoprecipitation experiments with α3- and β1-subunit-specific antibodies, consistent with their association as the α3β1-integrin receptor at the cell membrane. Treatment with blocking anti-α3 monoclonal antibody from day 0 delayed development of transepithelial resistance, reduced transepithelial resistance through day 5 compared with that in untreated AECs, and resulted in large subconfluent patches in monolayers viewed by scanning electron microscopy on day 3. These data indicate that α3- and β1-integrin subunits are expressed in AEC monolayers where they form the heterodimeric α3β1-integrin receptor at the cell membrane. Blockade of the α3-integrin subunit inhibits formation of confluent AEC monolayers. We conclude that the α3-integrin subunit modulates formation of AEC monolayers by virtue of the key role of the α3β1-integrin receptor in AEC adhesion. Copyright © 2000 the American Physiological Society.