Adhesion to the host cell surface is sufficient to mediate entry into epithelial cells.

The intestinal epithelium is the first physiological barrier breached by the Gram-positive facultative pathogen during an in vivo infection. binds to the epithelial host cell receptor E-cadherin, which mediates a physical link between the bacterium and filamentous actin (F-actin). However, the importance of anchoring the bacterium to F-actin through E-cadherin for bacterial invasion has not been tested directly in epithelial cells. Here we demonstrate that depleting αE-catenin, which indirectly links E-cadherin to F-actin, did not decrease invasion of epithelial cells in tissue culture. Instead, invasion increased due to increased bacterial adhesion to epithelial monolayers with compromised cell-cell junctions. Furthermore, expression of a mutant E-cadherin lacking the intracellular domain was sufficient for efficient invasion of epithelial cells. Importantly, direct biotin-mediated binding of bacteria to surface lipids in the plasma membrane of host epithelial cells was sufficient for uptake. Our results indicate that the only requirement for invasion of epithelial cells is adhesion to the host cell surface, and that E-cadherin-mediated coupling of the bacterium to F-actin is not required.