The Neurotrophins
The neurotrophins are composed of four proteins, all of which bind to the LNGFR: Nerve Growth Factor (NGF), Brain Derived Neurotrophic Factor (BDNF), Neurotrophin-3 (NT-3), and Neurotrophin-4 (NT-4).
Nerve growth factor, the prototypical growth factor, is a protein secreted by a neuron's target. NGF is critical for the survival and maintenance of sympathetic and sensory neurons. NGF is released from the target cells, binds to and activates its high-affinity receptor (TrkA), and is internalized into the responsive neuron. The NGF/TrkA complex is subsequently trafficked back to the cell body. This movement of NGF from axon tip to soma is thought to be involved in the long-distance signaling of neurons.
The activation of TrkA by NGF is critical in inducing the survival and differentiation caused by this growth factor.
However, NGF binds at least two receptors on the surface of cells that are capable of responding to this growth factor, TrkA (pronounced "Track A") and the LNGFR.
Read more about this topic: Low-affinity Nerve Growth Factor Receptor