Expression of a soluble functional form of the integrin α4β1 in mammalian cells

The integrin alpha(4)beta(1)(VLA4) has been expressed as a soluble, active, heterodimeric immunoglobulin fusion protein, cDNAs encoding the extracellular domains of the human alpha(4) and beta(1) subunits were fused to the genomic DNA encoding the human yl immunoglobulin Fc domain and functional integrin fusion protein was expressed as a secreted, soluble molecule from a range of mammalian cell lines. Specific mutations were introduced into the Fc region of the molecules to promote alpha(4)beta(1) heterodimer formation. The soluble alpha(4)beta(1)-Fc fusion protein exhibited divalent cation dependent binding to VCAM-1, which was blocked by the appropriate function blocking antibodies. The apparent K-d for VCAM-1 binding were similar for both the soluble and native forms of a(4)beta(1). In addition, the integrin-Fc fusion was shown to stain cells expressing VCAM-1 on their surface by FACs analysis. This approach for expressing soluble alpha(4)beta(1) should be generally applicable to a range of integrins.