Beta 1 integrins isolated from embryonic chicken fibroblasts bind to monomers and polymers of type I collagen

The avian integrin beta 1 subfamily consists of multiple alpha-beta subunit heterodimers. We employed two different physical states of type I collagen, monomers and fibrils, in the isolation and characterization of avian collagen integrins. Affinity chromatography showed that three integrins, tentatively designated alpha 155 beta 1 (band 1), alpha 5a beta 1, and alpha 3 beta 1 (band 2), bind fibrillar and monomeric collagen under physiological ionic conditions and require divalent cations for binding activity. Sodium chloride gradients (0-0.5 M) were used to assess the functional ability of the integrins to remain bound to the two forms of type I collagen. The results show that integrins elute from the two forms of collagen with distinct fractionation profiles. One integrin, alpha 155 beta 1, binds fibrillar collagen with relatively higher affinity than the other beta 1 receptors. This same avian integrin, alpha 155 beta 1, is immunoreactive with an antiserum (Hynes et al., 1989) raised against a peptide that corresponds to the entire alpha 5 cytoplasmic domain, and coincidently, part of the alpha 6 cytoplasmic domain (de Curtis et al., 1991). Cell biological studies employing double immunofluorescence show that integrins recognized by this antiserum co-localize with extracellular deposits of type I collagen.