NT-4 (Neurotrophin-4) is a member of the NGF family of neurotrophins that is comprised of at least four proteins including NGF, BDNF, NT-3, and NT-4/5. Neurotrophins are critical to the development of the central and peripheral nervous system and they play important roles in injury induced neuron regeneration. NT-3 is expressed in the prostate, thymus, placenta and skeletal muscle and promotes the survival of peripheral sensory sympathetic neurons. NT-4 is a secreted protein that primarily signals through the LNGFR and trkB receptors.