Plexin B1

Plexin B1 serves as the Semaphorin 4D receptor and functions as a regulator of developing neurons and a tumor suppressor protein for melanoma. The Sema4D-plexin B signaling complex regulates dendritic and axonal complexity. The activation of Plexin B1 by Sema4D produces an acute collapse of axonal growth cones in hippocampal and retinal neurons over the early stages of neurite outgrowth and promotes branching and complexity. As a tumor suppressor, plexin B1 abrogates activation of the oncogenic receptor, c-Met, by its ligand, hepatocyte growth factor (HGF), in melanoma. Furthermore, plexin B1 suppresses integrin-dependent migration and activation of pp125FAK and inhibits Rho activity. Plexin B1 is highly expressed in endothelial cells and its activation by Sema4D elicits a potent proangiogenic response. The Sema domain is located at the N-terminus and contains four disulfide bonds formed by eight conserved cysteine residues. It serves as a ligand-recognition and -binding module.