Plexin B1 (PLXNB1)

The cDNA sequence (FB7) was isolated by serendipity from a human fetal brain cDNA library. The SEP gene was expressed at highest levels in fetal kidney.

PLXNB1 is a receptor for the transmembrane semaphorin SEMA4D, also called CD100. Binding of SEMA4D to PLXNB1 stimulated tyrosine kinase activity of MET, resulting in tyrosine phosphorylation of both receptors. This effect was not found in cells lacking MET expression.This activity required the interaction of plexin B1 with RND1 , a small GTP-binding protein of the Rho family. Downregulation of RRAS activity by the plexin B1/RND1 complex was essential for the SEMA4D-induced growth cone collapse in hippocampal neurons.