Domain IVa of laminin alpha5 chain is cell-adhesive and binds beta1 and alphaVbeta3 integrins through Arg-Gly-Asp.

The globular domain IVa from the short arm region of mouse laminin alpha5 chain was obtained by recombinant production and shown to be a cell-adhesive substrate and to bind alphaVbeta3 integrin in solid-phase assays. These interactions were blocked by RGD peptides and a restricted panel of anti-integrin antibodies. The two RGD sequences present in alpha5IVa were shown by site-directed mutagenesis to make different contributions to cell adhesion but were equivalent in binding alphaVbeta3 integrin. A quantitative radioimmuno-inhibition assay was established based on domain alpha5IVa which demonstrated distinct amounts of alpha5 chain in various tissues, particularly in vessel walls. There it could play a role in angiogenesis steps requiring RGD-dependent integrins.