Semaphorins and Plexins

Semaphorins are a class of secreted and membrane proteins that act as axonal growth cone guidance molecules. They primarily act as short-range inhibitory signals and signal through multimeric receptor complexes. They are usually cues to deflect axons from inappropriate regions, especially important in neural system development. The major class of proteins that act as their receptors are called plexins.

Two distinct transmembrane receptor families have been identified as Semaphorin receptors. Neuropilins provide binding specificity for the class 3 Semaphorins, whereas Plexins, which also contain a Sema domain serve as signaling partners for class 3 Semaphorins and as functional receptors for transmembrane Semaphorins.