Plays an important role in signaling via the cell surface receptor PLXND1. Mediates reorganization of the actin cytoskeleton, leading to the retraction of cell projections. Promotes focal adhesion disassembly and inhibits adhesion of endothelial cells to the extracellular matrix. Regulates angiogenesis. Can down-regulate sprouting angiogenesis. Required for normal vascular patterning during embryogenesis. Induces the collapse and paralysis of neuronal growth cones. Plays an important role in ensuring the specificity of synapse formation (By similarity). Collapsin-1, -2, -3, and -5 bind to overlapping but distinct axon tracts. Strong binding to neuropilin is mediated by the carboxy third of the protein. Belongs to the semaphorin family.