Sema4D binds Plexin-B1 to induce repulsive or attractive effects in neuronal and nonneuronal cells. Plexins constitute a large family of transmembrane proteins that function as receptors for semaphorins and their interaction governs cell adhesion and migration in a variety of tissues. All B-class plexins can interact with the receptor tyrosine kinases Met and ErbB2. Upon binding of Sema4D to plexin-B1, the kinase activity of ErbB2 is increased resulting in tyrosine phosphorylation of both Plexin-B1 and ErbB2. ErbB2 has been shown to mediate Sema4D-induced growth cone collapse in hippocampal neurons by the activation of RhoA via plexinB1 and PDZRhoGEF/LARG.
Sequence alignment reveals the presence of 13 conserved tyrosine residues (highly conserved sites 1918, 1953, 2038) but the specific tyrosine residues phosphorylated in the cytoplasmic domain of plexins in response to semaphorin stimulation have not yet been identified.