The cell-binding domain of intimin from enteropathogenic Escherichia coli binds to beta(1) integrins

Bacteria interact with mammalian cells surface mole cules, such as integrins, to colonize tissues and evade immunological detection. Herein, the ability of intimin, an outer membrane protein from enteropathogenic Escherichia coli, to bind beta(1) integrins was investigated. Solid-phase binding assays revealed binding of the carboxyl-terminal 280 amino acids of intimin (Int280) to alpha(4) beta(1) and alpha(5) beta(1) integrins. The binding required divalent ions (in particular, it was enhanced by Mn2+) and was inhibited by an RGD-containing peptide. Nonderivatized Int280, but not Int280CS (like Int280 but with Cys-937 replaced by Ser) blocked the binding of biotinylated Int280 to integrins. Int280 did not efficiently inhibit beta(1), integrin binding of invasin from Yersinia pseudotuberculosis. Both intimin and invasin, immobilized on plastic surfaces, mediated adherence of resting or phorbol 12-myristate 13-acetate-activated human CD4(+) T cells, whereas fibronectin mediated the adherence of only activated T cells. T cell binding to intimin and invasin was integrin mediated because it was specifically blocked by an RGD containing peptide and by antibodies directed against the integrin subunits beta(1), alpha(4) and alpha(5). These results demonstrate a specific integrin binding activity for intimin that is related to, but distinct from, that of invasin.