Plexins act as functional receptors for members of the semaphorin family. Together they transmit repulsive axon guidance signals for semaphorins inside the axonal growth cone. The plexins act together with their co-receptors, neuropilins. Plexin-A1, in combination with neuropilins exhibits various functions in axon guidance, organogenesis, angiogenesis, tumorigenesis, and immune regulation.Plexin-A1 also plays an important role in the developmental stages of chick heart by working as a receptor for one of the transmembrane semaphorins. In addition Plexin-A1 expressed in dendritic cells is involved in T-dendritic cell interactions in the immune system
