JAM‐A regulates barrier function through a pathway distinct from that controlling cell migration

Abstract

Tight junctions (TJs) are critical for barrier function by controlling the paracellular passage of solutes and preventing influx of toxins and pathogens. We have reported that the TJ protein Junctional Adhesion Molecule A (JAM‐A) regulates intestinal epithelial barrier by dimerization‐dependent signal(s), however the pathway is not understood. Given our previous findings linking JAM‐A to β1 integrin–mediated cell migration through Afadin, PDZ‐GEF2 and Rap1a, we used an siRNA mediated approach to test if these elements were important in JAM‐A regulation of barrier. Here we report that JAM‐A modulates barrier by a pathway distinct from that regulating cell migration. Loss of Afadin, PDZ‐GEF1, and Rap2c but not PDZ‐GEF2, Rap1a/b or Rap2b impaired barrier by a similar extent to that observed with JAM‐A loss. Since Rap2 has not been characterized in the intestine, we also show that Rap2 co‐localizes with JAM‐A at TJs in healthy human colonic epithelium. We conclude that JAM‐A‐mediated regulation of epithelial function is dependent on multiple divergent pathways involving small GTPases and speculate that JAM‐A dependent Rap2c activation regulates barrier through effects on the peri‐junctional cytoskeleton.