The role of semaphorins and their receptors in platelets: Lessons learned from neuronal and immune synapses.

During thrombus formation, activated platelets come into close and increasingly stable contact with each other. This produces a microenvironment in which soluble agonists can accumulate, and proteins on the surface of adjacent platelets can directly interact with each other, potentially modulating subsequent thrombus growth and stability. In some ways, this microenvironment resembles the synapses that support signal propagation between neurons and the exchange of information between T-cells, B-cells, and dendritic cells. Drawing on this analogy, this brief review discusses the role of semaphorins and their receptors in platelets, two protein families that have previously been defined by their role at cell:cell contacts, in both the developing nervous system and adaptive immunity.