Neurotrophins are a family of small proteins that bind to and activate the members of receptor protein tyrosine kinase family. They also bind the low-affinity neurotrophin receptor (p75). Neurotrophins have a broad spectrum of biological functions in several tissues, but they are best studied in the developing nervous system. Neurotrophins are secreted from cells of many tissues, picked up by terminals of the competent neurons innervating these tissues, and transported to the neuronal perikarya. In developing neurons, this leads to neutralization of the naturally occurring neuronal death program and thereby regulates the density of tissue innervation. In neurobiology, the term "trophic" actually means antiapoptotic, rather than nutritional. In addition, neurotrophins can induce neurite outgrowth and direct the course of the neurites.
Biomedical Reviews 1995; 4: 15-27.