Coreceptor for SEMA3A, SEMA3C, SEMA3F and SEMA6D. Necessary for signaling by class 3 semaphorins and subsequent remodeling of the cytoskeleton. Plays a role in axon guidance, invasive growth and cell migration. Class 3 semaphorins bind to a complex composed of a neuropilin and a plexin. The plexin modulates the affinity of the complex for specific semaphorins, and its cytoplasmic domain is required for the activation of down-stream signaling events in the cytoplasm (By similarity). Interacts directly with NRP1 and NRP2. Interacts with FARP2, RND1 and KDR/VEGFR2. Binding of SEMA3A leads to dissociation of FARP2 (By similarity). Detected in fetal brain, lung, liver and kidney. Belongs to the plexin family.