What Is a Brain-Derived Neurotrophic Factor?
Brain-derived neurotrophic factor (BDNF) is a protein with neurotrophic effects first discovered in pig brain by Barde and others in 1982. Brain-derived neurotrophic factors and their receptors are widely expressed in the nervous system. A small molecule dimer protein BDNF structure, distribution and signal transduction BDNF molecular monomer is a secreted mature polypeptide composed of 119 amino acid residues, the isoelectric point of the protein is 9.99, the relative molecular weight is 3.5 × 103, mainly It consists of -sheet and random coil secondary structure, and contains three disulfide bonds, which is a basic protein. BDNF is distributed in a wide range of areas such as the central nervous system, peripheral nervous system, endocrine system, bone and cartilage tissue, but is mainly expressed in the central nervous system, with the highest levels in the hippocampus and cortex. 
Brain-derived neurotrophic factor
- BDNF is the most abundant in the body
- BDNF not only binds to strong receptors (TrkA, TrkB, TrkC) such as the Trk family, but also acts as a member of the tumor necrosis factor family with a molecular weight of 75 kD, a neurotrophin receptor (P75 neurotrophin receptor). Corresponding biological effects. The P75 receptor is not necessary for the function of neurotrophins (NTs). The role of P75 may be to enhance the affinity of trk receptors and NTs, which is beneficial to nerve terminal uptake and retrograde transport. BDNF exerts its biological function depends on its specific receptor binding. There are at least two BDNF receptors, trkB and P75, on the nerve cell membrane. P75 is a BDNF low-affinity protein receptor and can bind to any NTs Its content in the brain is higher than trkB, but its effect on BDNF is unclear. It is speculated that the binding of BDNF to the P75 receptor may affect the release of vesicles and neurotransmitters by inhibiting the activity of CaMKn and MAP-kinase, and then affect the ability of learning and memory. The specific mechanism needs further study. One experiment used P75 receptor-human and rat hippocampal neuron cultures, and found that there was no significant difference between the BDNF group and the control group. At present, it is thought that the P75 receptor has the effect of enhancing the affinity of the Trk family receptor and BDNF, and its binding to BDNF alone has not been reported to have its special biological function.