Schematic representation of possible signal transduction pathways triggered by Sema3A. This semaphorin binds a complex containing the receptor proteins Plex-A1 and NP-1, as well as other, still poorly characterized signal transducing molecules. In neurons, some of the downstream events, including reorganization of the actin cytoskeleton and the consequent collapse of the axonal growth cone, are also influenced by pertussis toxin–sensitive (PTX-sensitive) G proteins. The CRMP appears to be central to several of the cellular responses to Sema3A.