PLXNB1

PLXNB1 is the gene that encodes Plexin-B1, a transmembrane receptor in the plexin family that mediates signaling for class 4 semaphorins. In humans, Plexin-B1 is expressed in the nervous system, vasculature, and various other tissues, and it contributes to processes such as neuronal development, axon guidance, and cell movement.

The Plexin-B1 protein has an extracellular sema domain that binds semaphorin ligands, followed by adjacent PSI and IPT domains, a single-pass transmembrane region, and a cytoplasmic region containing a GTPase-activating protein (GAP)–like domain. Ligand binding typically involves semaphorins such as Sema4D (CD100) and other class 4 semaphorins, and signaling can be influenced by co-receptors or interacting proteins that modulate downstream responses.

Upon activation by semaphorin binding, Plexin-B1 modulates small GTPases, including R-Ras and potentially other Rho family members, leading to changes in the cytoskeleton, cell adhesion, and motility. In some cellular contexts, Plexin-B1 signaling requires cooperation with receptor tyrosine kinases or other co-receptors, which can influence pathways that govern migration, shape changes, and invasive behavior.

Functionally, Plexin-B1 participates in axon guidance and vascular patterning during development and also influences cellular behavior in adult tissues. Altered PLXNB1 signaling has been associated with cancer cell invasion and progression in certain contexts, though these effects are context-dependent. Mouse studies support a role for Plexin-B1 in neurite guidance and vascular development, underscoring its conserved function in vertebrate biology.