Neurotrophin-4 (NT-4), also known as NT-5, is a neurotrophic factor structurally related to β-NGF, BDNF, and NT-3. Human NT-4 shares 48 - 52% aa sequence identity with human β-NGF, BDNF, and NT-3.Neurotrophins have six conserved cysteine residues that are involved in the formation of three disulfide bonds. NT-4 is expressed highest levels in prostate, lower levels in thymus, placenta, and skeletal muscle. NT-4 binds and induces receptor dimerization and activation of TrkB. NT-4 can signal through TrkB receptors and promotes the survival of peripheral sensory sympathetic neurons.

Recombinant human Neurotrophin-4 (rhNT-4) produced in E.coli is a noncovalently linked homodimer containing two non-glycosylated polypeptide chains of 131 amino acids. A fully biologically active molecule, rhNT-4 has a molecular mass of 28.1kDa analyzed by reducing SDS-PAGE and is obtained by proprietary chromatographic techniques at ExCell Bio.