Interaction between laminin, fibronectin and the light chain of the H2 complex. Attachment of glomerular cells to basement membranes by linking the endoskeleton to the exoskeleton by a transmembrane protein

Abstract

At present the detailed mechanism for transmembrane interactions is not known and a protein linked to the endoskeleton as well as to the exoskeleton has not been described as yet. The H2 complex, a transmembrane protein, consists of heavy and light chains, the latter is named beta-2-microglobulin. In order to look for an association of beta-2-microglobulin with an exoskeleton protein, we examined the extracellular matrix proteins, collagen type I, type IV, fibronectin, amyloid P, the solubilized glomerular basement membrane and laminin in respect to their interaction with the light chain. The heavy chain is known to bind strongly to the endoskeleton protein actin. Only laminin and the glomerular basement membrane bound firmly to the beta-2-microglobulin; 3 M urea was necessary to dissociate the formed complex. Incubation with beta-2-microglobulin antibody prevented binding of beta-2-microglobulin to laminin and the glomerular basement membrane on affinity chromatography columns. Antiserum to the glomerular basement membrane in turn prevented binding of beta-2-microglobulin to the glomerular basement membrane, whereas antibodies against the basement membrane collagen type IV failed to inhibit this binding to the glomerular basement membrane. Beta-2-microglobulin also bound to fibronectin but this complex was dissociated with 1 M urea. In a rosette assay beta-2-microglobulin antibody and antiserum to the glomerular basement membrane reduced attachment of glomerular cells to beads coupled with laminin and solubilized glomerular cells to beads coupled with laminin and solubilized glomerular basement membrane.(ABSTRACT TRUNCATED AT 250 WORDS)