Neuropilins are 140-kDa vertebrate cell surface receptors that bind neuronal guidance molecules during neural development and axonal outgrowth, and modulate VEGF-mediated angiogenesis. NEUROPILIN-1 and NEUROPILIN-2 differ in their binding specificities, and are distributed complementarily in regions of the developing nervous system. Neuropilins are receptors for secreted CLASS 3 SEMAPHORINS as well as for vascular endothelial growth factors, and may form hetero- or homodimers. They may also interact synergistically with plexins and with VEGF RECEPTORS to form receptor complexes with distinct affinities and specificities. Neuropilin binding specificity is determined by CUB and coagulation-factor-like domains in the extracellular portion of the molecule, while a MAM domain is essential for SIGNAL TRANSDUCTION. X