Neuropilin-1 (Npn-1) is a transmembrane glycoprotein that regulates axon guidance and angiogenesis. Distinct Neuropilin-1 domains mediate its binding to heparin, the heparin-binding forms of VEGF and PlGF (PlGF2), and Semaphorin 3. Neuropilin-1 can form homo- and hetero-oligomers with Neuropilin-2. Neuropilins show partially overlapping expression in neuronal and endothelial cells during development. They mediate axon repulsion on sensory and sympathetic neurons through binding to Class III Semaphorins, Plexin A3, and Plexin A4. They also associate with VEGF R2 and function as coreceptors for VEGF. Neuropilin-1 is preferentially expressed in developing or remodeling arteries, epithelial cells, and carcinomas, while Neuropilin-2 is primarily found in veins and lymphatics. Neuroplin-1 is additionally expressed on dendritic cells where it mediates DC-induced T cell proliferation.