Semaphorins as signals for cell repulsion and invasion

Semaphorins are a large family of secreted and transmembrane signaling proteins that regulate axonal guidance in the developing nervous system. Recent studies suggest that semaphorin receptors also act in such diverse processes as lymphocyte activation, control of vascular endothelial cell motility, and lung branching morphogenesis. Here, we describe the current knowledge of the intracellular signaling pathways employed by these molecules, focusing on several candidate molecules that help reorganize the cytoskeleton or alter patterns of intracellular transport during neuronal outgrowth. We then consider other cellular events, occurring outside of the nervous system, that are mediated by these semaphorins, their receptors, and associated molecules.