The low affinity nerve growth factor receptor (NGF R), also named p75 neurotrophin receptor, is a type I transmembrane protein that belongs to the tumor necrosis factor receptor family and has been designated TNFRSF16. NGF R cDNA encodes a 427 amino acid (aa) residue precursor protein with a 28 aa residue signal peptide, a 222 aa residue extracellular domain, a 22 aa residue transmembrane domain and a 155 aa residue intracellular domain. The extracellular region contains four cysteine-rich domains and binds NGF, BDNF, NT-3 and NT-4 approximately equally with low affinity. The cytoplasmic region of the receptor contains a subtype 2 death domain.
NGF R expression has been shown to occur widely during development and in the adult. Expression has been detected in both neuronal and non-neuronal cells. NGF R was originally reported to function as a positive regulator of TrkA activity. NGF R has also been shown to signal by itself. Depending on its cellular environment, NGF R has now been shown to regulate cell migration, gene expression and to mediate apoptosis. Recombinant NGF R/Fc chimera binds NGF with high affinity and is a potent NGF antagonist. Naturally occurring truncated NGF R containing the extracellular domain and lacking the transmembrane or intracellular domain has been detected in vivo in urine, plasma and in the amniotic fluid of humans and rats (1 - 3).
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