Intestinal epithelial tight junctions as targets for enteric bacteria-derived toxins.

The application of a multidisciplinary approach to study bacterial pathogenesis, along with the recent sequencing of entire microbial genomes have made possible discoveries that are changing the way scientists view the bacterium-host interaction. Today, research on the molecular basis of the pathogenesis of infectious diarrheal diseases of necessity transcends established boundaries between microbiology, cell biology, intestinal pathophysiology, and immunology. Novel multidisciplinary approaches led to the discovery of new bacteria-host cell interactions involving signals regulating intestinal permeability through the modulation of cell cytoskeleton and intercellular tight junctions (TJ). A century ago, TJ were conceptualized as a secreted extracellular cement forming an absolute and unregulated barrier within the paracellular space. Biological studies of the past several decades have shown that TJ are dynamic structures subjected to structural changes that dictate their functional status under a variety of developmental, physiological, and pathological circumstances. To meet the many diverse physiological challenges to which the intestinal epithelial barrier is subjected, TJ must be capable of rapid and coordinated responses. This requires the presence of a complex regulatory system that orchestrates the state of assembly of the TJ multiprotein network. Many pathogenic bacteria exploit this system to accomplish their pathogenic strategies by ultimately modulating intestinal permeability.