Promotes a prolonged MAP-kinase signaling by neurotrophins through activation of a Rap1-dependent mechanism.Provides a docking site for the CRKL-C3G complex, resulting in Rap1-dependent sustained ERK activation.May play an important role in regulating postsynaptic signal transduction through the syntrophin-mediated localization of receptor tyrosine kinases such as EPHA4.In cooperation with SNTA1 can enhance EPHA4-induced JAK/STAT activation.Plays a role in nerve growth factor (NGF)-induced recruitment of RAPGEF2 to late endosomes and neurite outgrowth.