Neural Crest Cell Interactions with Laminin: Structural Requirements and Localization of the Binding Site for α1β1 Integrin

We have identified the sites of neural crest cell interaction with laminin in vitro by examining their ability to attach to and migrate on proteolytic fragments of the molecule and the ability of fragment-specific antibodies to inhibit these interactions. The binding site on laminin was localized to the E8 domain on the long arm of laminin, as well as the T8′ fragment within this domain, but not the E1′, E3, or E4 fragments. Only subfragments containing the carboxy-terminal rod-like portion of the A chain plus the corresponding B1 and B2 chains retained the attachment-promoting activity of the parent E8 fragment. In addition, interactions required maintenance of the triple-stranded and α-helical coiled-coil structure of this domain. Reduction and alkylation of laminin and the E8 and T8 fragments significantly reduced neural crest cell attachment and migration. An antiserum against chick α1 integrin reduced migration and adhesion of neural crest cells on an intact laminin-nidogen complex, the E8 fragment, and all its active subfragments. Furthermore, we observed that neural crest cells modified laminin substrata prepared in the absence of divalent cations. Early stable attachment to these substrata was mediated by an integrin other than α1, whereas later attachment and migration were mediated by α1 integrins. Our results suggest that neural crest cells selectively bind to the B1-A-B2 mid-portion (T8′) of the E8 domain of laminin, requiring structural integrity of this region and that they modify laminin substrata as a result of prolonged cell-matrix interactions