CD321/JAM-A
CD321, junctional adhesion molecule A (JAM-A, F11R), is a small immunoglobulin superfamily protein with two extracellular Ig-like domains that localizes to tight junctions of endothelial and epithelial monolayers. Homophilic and heterophilic contacts seal intercellular clefts, tune paracellular permeability and give transmigrating leukocytes a foothold alongside PECAM-1 and CD99. On platelets and leukocytes, JAM-A engages LFA-1 and supports adhesive interactions with the vessel wall, and mammalian reoviruses exploit the molecule as their entry receptor. Its cytoplasmic tail associates with cingulin, PAR-3 and ZO-1, linking junctional adhesion to cell polarity. Recombinant JAM-A serves barrier-function and virology assays.
