JAM-A associates with ZO-2, afadin, and PDZ-GEF1 to activate Rap2c and regulate epithelial barrier function

• Authors: Ana C Monteiro, Emory University; Ronen Sumagin, Emory University; Carl R Rankin, Emory University; Giovanna Leoni, Emory University; Michael J Mina, Emory University; Dirk M Reiter, University of Tübingen; Thilo Stehle, University of Tübingen; Terence S Dermody, Vanderbilt University; Stacy A Schaefer, Emory University; Randy A Hall, Emory University; Asma Nusrat, Emory University; Charles Parkos, Emory University
• Journal Title: Molecular Biology of the Cell
• Volume: Volume 24, Number 18
• Publisher: American Society for Cell Biology | 2014-09, Pages 2849-2860
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1091/mbc.E13-06-0298
• Subjects: Health Sciences, Pathology; Health Sciences, Pharmacology; Biology, Cell

Abstract

Intestinal barrier function is regulated by epithelial tight junctions (TJs), structures that control paracellular permeability. Junctional adhesion molecule-A (JAM-A) is a TJ-associated protein that regulates barrier; however, mechanisms linking JAM-A to epithelial permeability are poorly understood. Here we report that JAM-A associates directly with ZO-2 and indirectly with afadin, and this complex, along with PDZ-GEF1, activates the small GTPase Rap2c. Supporting a functional link, small interfering RNA–mediated down-regulation of the foregoing regulatory proteins results in enhanced permeability similar to that observed after JAM-A loss. JAM-A–deficient mice and cultured epithelial cells demonstrate enhanced paracellular permeability to large molecules, revealing a potential role of JAM-A in controlling perijunctional actin cytoskeleton in addition to its previously reported role in regulating claudin proteins and small-molecule permeability. Further experiments suggest that JAM-A does not regulate actin turnover but modulates activity of RhoA and phosphorylation of nonmuscle myosin, both implicated in actomyosin contraction. These results suggest that JAM-A regulates epithelial permeability via association with ZO-2, afadin, and PDZ-GEF1 to activate Rap2c and control contraction of the apical cytoskeleton.