NGF is the first member of the neurotrophin-family trophic
factors. NGF regulates the growth, maintenance, proliferation, and survival of certain target neurons through activation of the high affinity receptor, tropomyosin receptor
kinase A (TrkA). NGF is also involved in apoptosis through
binding to the low affinity receptor, p75NTR. NGF consists
of three types of subunits, α, β, and γ, and the β-subunit is
solely responsible for the nerve growth stimulating activity of
NGF.