Reducing cell–cell stickiness with JAM-C

Most cell junction proteins increase endothelial cell–cell adhesion. But junction adhesion molecule-C (JAM-C), despite its sticky name, loosens vascular endothelial cell connections, thus allowing increased blood vessel permeability.

Increasing the permeability of small blood vessels is essential for new vessels to form and for leukocytes to escape the circulation and enter surrounding tissues during inflammation and tissue repair. Permeability is thought to be controlled by tight junctions between neighboring cells. Most tight junction components promote cell–cell adhesion and thus reduce permeability. But Orlova et al. (page 2703) show that the tight junction protein JAM-C does the opposite—it promotes permeability. Indeed JAM-C is the first junctional molecule reported to behave this way.

Using dye tracking, the team showed that knocking down JAM-C reduced endothelial permeability both in vitro and in vivo. The permeability-promoting effect...