Participation of Integrinα5β1 in the Fibronectin-Mediated Adherence of EnteroaggregativeEscherichia colito Intestinal Cells

Adherence to the intestinal epithelia is a key feature in enteroaggregative Escherichia coli (EAEC) infection. The aggregative adherence fimbriae (AAFs) are involved in EAEC interaction with receptors at the surface of intestinal cells. We and others have demonstrated that fibronectin is a receptor for AAF/II fimbriae. Considering that the major cellular receptor of fibronectin is integrin α 5 β 1, in this study we evaluated the participation of this receptor in the fibronectin-mediated adherence of EAEC strain 042 to intestinal cells. We found that EAEC strain 042 has the ability to bind directly and indirectly to integrin α 5 β 1; direct binding was not mediated by AAF/II fimbriae and indirect binding was mediated by AAF/II and fibronectin. Coimmunoprecipitation assays confirmed the formation of the complex AafA/fibronectin/integrin α 5 β 1. To evaluate EAEC adherence to intestinal cells, T84 cells were incubated with fibronectin and an antibody that blocks the interaction region of integrin α 5 β 1 to fibronectin, the RGD site. Under these conditions, we found the number of adherent bacteria to epithelial cells significantly reduced. Additionally, fibronectin-mediated adherence of EAEC strain 042 was abolished in HEp-2 cells transfected with integrin α 5 shRNA. Altogether, our data support the involvement of integrin α 5 β 1 in the fibronectin-mediated EAEC binding to intestinal cells.