Cell surface receptor for SEMA4C, SEMA4D and SEMA4G that plays an important role in cell-cell signaling (By similarity). Plays a role in glutamatergic synapse development and is required for SEMA4A-mediated excitatory synapse development (By similarity). Binding to class 4 semaphorins promotes downstream activation of RHOA and phosphorylation of ERBB2 at 'Tyr-1248' (By similarity). Required for normal differentiation and migration of neuronal cells during brain corticogenesis and for normal embryonic brain development (By similarity). Regulates the migration of cerebellar granule cells in the developing brain (By similarity). Plays a role in RHOA activation and subsequent changes of the actin cytoskeleton (PubMed:12183458). Plays a role in axon guidance, invasive growth and cell migration (PubMed:15184888). May modulate the activity of RAC1 and CDC42 (By similarity). Monomer, and heterodimer with PLXNB1 (PubMed:12533544). Interacts with SEMA4C, SEMA4D and SEMA4G (By similarity). Interacts with MET (PubMed:15184888). Interacts with ARHGEF11 and ARHGEF12 (PubMed:12183458). May also interact with MST1R (PubMed:15184888). Belongs to the plexin family.