Apically exposed, tight junction-associated beta 1-integrins allow bindingand YopE-mediated perturbation of epithelial barriers by wild-type Yersinia bacteria

Using polarized epithelial cells, primarily MDCK-1, we assessed the mode of binding and effects on epithelial cell structure and permeability of Yersi nia pseudotuberculosis yadA-deficient mutants. Initially, all bacteria exce pt the invasin-deficient (inv) mutant adhered apically to the tight junctio n areas. These contact points of adjacent cells displayed beta 1-integrins together with tight junction-associated ZO-1 and occludin proteins. Indeed, beta 1-integrin expression mas maximal in the tight junction area and then gradually decreased along the basolateral membranes. Wild-type bacteria al so opened gradually the tight junction to paracellular permeation of differ ent-sized markers, viz., 20, 40-, and 70-kDa dextrans and 45-kDa ovalbumin, as well as to their own translocation between adjacent cells in intimate c ontact with beta 1-integrins. The effects on the epithelial cells and their barrier properties could primarily be attributed to expression of the Yers inia outer membrane protein YopE, as the yopE mutant bound but caused no cy totoxicity. Moreover, the apical structure of filamentous actin (F-actin) w as disturbed and tight junction-associated proteins (ZO-1 and occludin) wer e dispersed along the basolateral membranes. It is concluded that the Yersi nia bacteria attach to beta 1-integrins at tight junctions. Via this locali zed injection of YopE, they perturb the F-actin structure and distribution of proteins forming and regulating tight junctions. Thereby they promote pa racellular translocation of bacteria and soluble compounds.