Expression of a soluble functional form of the integrin alpha(4)beta(1) inmammalian cells

The integrin alpha(4)beta(1)(VLA4) has been expressed as a soluble, active, heterodimeric immunoglobulin fusion protein, cDNAs encoding the extracellu lar domains of the human alpha(4) and beta(1) subunits were fused to the ge nomic DNA encoding the human yl immunoglobulin Fc domain and functional int egrin fusion protein was expressed as a secreted, soluble molecule from a r ange of mammalian cell lines. Specific mutations were introduced into the F c region of the molecules to promote alpha(4)beta(1) heterodimer formation. The soluble alpha(4)beta(1)-Fc fusion protein exhibited divalent cation de pendent binding to VCAM-1, which was blocked by the appropriate function bl ocking antibodies. The apparent K-d for VCAM-1 binding were similar for bot h 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 g enerally applicable to a range of integrins.