UNMASKING OF INTESTINAL EPITHELIAL LATERAL MEMBRANE BETA-1 INTEGRIN CONSEQUENT TO TRANSEPITHELIAL NEUTROPHIL MIGRATION IN-VITRO FACILITATESINV-MEDIATED INVASION BY YERSINIA-PSEUDOTUBERCULOSIS

Idiopathic intestinal disease states characterized by active inflammat ion associated with transepithelial migration of neutrophils may, para doxically, be associated with an increased risk of infection by enteri c pathogens. Although the specific ligands with which various intestin al pathogens associate remain largely unknown, it is thought that many reside on the basolateral membrane. For example, beta 1 integrin, a b asolateral membrane protein, mediates the specific interaction between epithelial cells and the inv gene product (invasin) on the surface of Yersinia pseudotuberculosis. Our observations indicate that neutrophi l migration across model T84 cell intestinal epithelia produced transi ent separation of epithelial cells at sites of neutrophil migration, r esulting in microdiscontinuities that remained unsealed for several ho urs. We hypothesized that such sites of microdiscontinuities would yie ld a potential route for luminal pathogens to gain access to basolater al ligands and, thus, provide a window of risk for enteric infection. The surface biotinylation and fluorescence localization studies report ed here revealed that, as in natural intestinal epithelia, beta 1 inte grin was strictly polarized to the basolateral membrane in confluent T 84 monolayers. However, the transient microdiscontinuities resulting f rom neutrophil migration permitted access to beta 1 integrin from the apical reservoir. Coincident with such basolateral exposure of beta 1 integrin, monolayers became susceptible to invasion by Y. pseudotuberc ulosis. Fluorescence localization indicated that Y. pseudotuberculosis selectively associated with monolayers at sites where small discontin uities resulting from neutrophil transmigration were found. An increas ed risk for Y. pseudotuberculosis infection was specifically related t o exposure of beta 1 integrin (normally concealed by tight junctions) to the apical compartment, as Y. pseudotuberculosis cells lacking the inv gene were unable to invade following neutrophil transepithelial mi gration. Following closure of the microdiscontinuities associated with neutrophil migration, a small pool of beta 1 integrin remained apical ly localized, presumably due to incomplete repolarization. However, th is small apical pool of beta 1, integrin was insufficient to support a detectable increased risk of Yersinia infection. Together, these obse rvations indicate that by transiently perturbing monolayer continuity, neutrophil transepithelial migration is associated with a window of r isk in which luminal pathogens can access basolateral ligands web as b eta 1 integrin.