A comparative molecular force spectroscopy study of homophilic JAM-A interactions and JAM-A interactions with reovirus attachment protein σ1

JAM-A belongs to a family of immunoglobulin-like proteins called junctional adhesion molecules (JAMs) that localize at epithelial and endothelial intercellular tight junctions. JAM-A is also expressed on dendritic cells, neutrophils, and platelets. Homophilic JAM-A interactions play an important role in regulating paracellular permeability and leukocyte transmigration across epithelial monolayers and endothelial cell junctions, respectively. In addition, JAM-A is a receptor for the reovirus attachment protein, sigma 1. In this study, we used single molecular force spectroscopy to compare the kinetics of JAM-A interactions with itself and sigma 1. A chimeric murine JAM-A/Fc fusion protein and the purified sigma 1 head domain were used to probe murine L929 cells, which express JAM-A and are susceptible to reovirus infection. The bond half-life [t(1/2)) of homophilic JAM-A interactions was found to be shorter (k(off)(o) = 0.688 +/- 0.349 s(-1)) than that of sigma 1/JAM-A interactions (k(off)(o) = 0.067 +/- 0.041 s-1). These results are in accordance with the physiological of functions of JAM-A and sigma 1. A short bond lifetime imparts a highly dynamic nature to homophilic JAM-A interactions for regulating tight junction permeability while stable interactions between sigma 1 and JAM-A likely anchor the virus to the cell surface and facilitate viral entry. Copyright (C) 2008 John Wiley & Sons, Ltd.