Cooperative activity of alpha 4 beta 1 and alpha 4 beta 7 integrins in mediating human B-cell lymphoma adhesion and chemotaxis on fibronectin throughrecognition of multiple synergizing binding sites within the central cell-binding domain

We have quantitated the relative contributions of the constitutively active alpha 4 beta 1 and alpha 4 beta 7 integrins and the domains embodying thei r cognate binding sites in mediating human B-cell lymphoma adhesion and che motaxis on fibronectin. By cooperating, the central cell-binding and IIICS carboxyterminal domains were entirely responsible for the adhesion activity displayed by fibronectin, and their relative contribution to this process was estimated to be 30% versus 70%. Assessment of the leukocyte-substrate b inding strength (ie, dynes/cell) indicated a 10-fold higher avidity of the cell-IIICS domain interaction. The two integrins interchangeably recognized both domains, but differed quantitatively in their participation in the ad hesive event, as well as in domain preference. The use of 3Fn (according to the nomenclature proposed by Bork and Koonin [Curr Opin Struct Biol 6:366, 1996] for the type III fibronectin modules) module-specific antibodies and recombinant polypeptides showed that alpha 4 integrins recognized both the RGD sequence (3Fn10) and an apparently novel synergistic site located with in the 3Fn8 module; even in this case, the integrins displayed a distinct b inding site preference. Interleukin-1 beta (IL-1 beta)/IL-2-induced chemota xis also involved cooperative function of the central cell-binding and IIIC S domains, but the mechanisms regulating this phenomenon differed markedly from those controlling cell adhesion. First, the relative contribution of t he individual domains was comparable, but neither of the individual domains promoted migration to the extent observed on intact fibronectin. Secondly, alpha 4 beta 1and alpha 4 beta 7 integrins were both involved in the domai n-binding necessary for initiation of migration, but the relative contribut ion of each receptor in the chemotactic process was less disparate than for initial cell adhesion. Thirdly, the mode by which chemotactic B-lymphoma m ovement was supported by the central cell-binding domain differed from that sustaining cell adhesion in that it involved independent recognition of ei ther the 3Fn8 or the 3Fn9 module, which acted in synergy with the 3Fn10 mod ule. Our data provide novel evidence concerning the relative importance of the constitutively active alpha 4 beta 1 and alpha 4 beta 7 integrins for t he interaction of B-cell lymphoma cells with fibronectin, and they emphasiz e a multiple and diverse recognition of sites responsible for either anchor age or locomotion of tumor leukocytes on this matrix molecule. (C) 1999 by The American Society of Hematology.