Nerve
growth factor receptor (NGFR) is also referred to as p75(NTR)
due to its molecular mass and its ability to bind at low
affinity not only NGF), but also other neurotrophins, including
brain-derived neurotrophic factor , neurotrophin-3 , and
neurotrophin-4/5. At the time of its discovery, NGFR was
considered a unique type of protein. Subsequently, however,
a large superfamily of tumor necrosis factor receptors
were found to share the overall structure of NGFR 4 extracellular
ligand-binding, cysteine-rich repeats, or CRs, and signaling
through association with, or disassociation from, cytoplasmic
interactors). The identification of this superfamily helped
elucidate some of the biologic functions of NGFR, including
its ultimate involvement in the nuclear factor kappa-B
(NFKB) and apoptosis pathways. As a monomer, NGFR binds
NGF with low affinity. Higher affinity binding is achieved
by association with higher molecular mass, low-affinity
neurotrophin receptors, namely the tropomyosin receptor
kinases, TRKA (NTRK1), TRKB (NTRK2), and TRKC (NTRK3).
TRKA, TRKB, and TRKC are specific for or 'preferred by'
NGF, NTF5 and BDNF, and NTF3, respectively . NTF3 also
binds to TRKA and TRKB, but with significantly lower affinity.
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