Semaphorin 3A displays a punctate distribution on the surface of neuronal cells and interacts with proteoglycans in the extracellular matrix

Secreted semaphorins are essential for neural development and continue to be expressed in subpopulations of adult neurons, where they subserve as yet unknown functions. We employed functional myc- and GFP-tagged Sema3A proteins to obtain insight in the localization of Sema3A in neuronal cells. Sema3A localized to both axons and dendrites of cortical neurons. GFP-Sema3A exhibited a characteristic punctate distribution on the surface of Neuro-2a cells, localized to migratory pathways of cultured cells, and co-localized with and induced clustering of its receptor component neuropilin-1. Treatment with excess glycosaminoglycans and chondroitinase ABC resulted in the removal of cell surface Sema3A. Heparin enhanced Sema3A's binding to neuropilin-1-expressing cells and potentiated its growth cone collapsing activity. Together, these results indicate that association with proteoglycans in the extracellular matrix of neuronal cells plays an important role in the localization of the chemorepulsive guidance cue Sema3A, and that this interaction may enhance its biological activity.