CELL-COLLAGEN ADHESION IS INHIBITED BY MONOCLONAL-ANTIBODY-33.4 AGAINST THE RAT ALPHA(1)-INTEGRIN SUBUNIT

A monoclonal antibody (mAb 33.4) is described which inhibits the adhesion and spreading of an adherent cell line (A-cells), established from Morris hepatoma 7777 and isolated hepatocytes on collagen IV but not on laminin, fibronectin, and vitronectin. mAb 33.4 retains its immunological activity after immobilization and covalent cross-linking to Protein G-Sepharose and is therefore a suitable tool for the preparative equimolar purification of two proteins with M(r) of 130 and 190 kDa from detergent-solubilized membrane fractions by immunoaffinity chromatography. The 190-kDa protein was identified as rat alpha(1)-integrin subunit by N-terminal amino acid sequencing, while the 130-kDa protein was specifically stained by a beta(1)-integrin subunit-specific antiserum. In immunoblot analysis mAb 33.4 recognized the 190-kDa band, suggesting that it is specific for the rat alpha(1)-integrin subunit. The epitope recognized by mAb 33.4 is conformation-dependent because the staining in immunoblots was very strong if the SDS-PAGE was performed in the absence of reducing agents. The expression of alpha(1) beta(1)-integrin in sinusoidal hepatocyte membrane domains of liver sections is shown by mAb 33.4 and antisera raised against the rat alpha(1)- and beta(1)-integrin subunits. (C) 1994 Academic Press, Inc.