Tropomyosin receptor kinase B (TrkB), also known as tyrosine receptor kinase B, or BDNF/NT-3 growth factors receptor or neurotrophic tyrosine kinase, receptor, type 2 is a protein that in humans is encoded by the NTRK2 gene.



TrkB is a receptor for brain-derived neurotrophic factor (BDNF).



Gene location  Chromosome 9.



Tropomyosin receptor kinase B is a  catalytic receptor for several “neurotrophins”, which are small protein growth factors that induce the survival and differentiation of distinct cell populations. 



The neurotrophins that can activate TrkB include: BDNF (Brain Derived Neurotrophic Factor), neurotrophin-4 (NT-4), and neurotrophin-3 (NT-3).



TrkB mediates the effects of these neurotrophic factors: 


neuronal differentiation and survival. 



Activation of the TrkB receptor can lead to down regulation of the KCC2 chloride transporter in cells of the CNS.



The TrkB receptor is part of the large family of receptor tyrosine kinases. 



A tyrosine kinase is an enzyme which is capable of adding a phosphate group to certain tyrosines on target proteins, or substrates.



A receptor tyrosine kinase is a tyrosine kinase  which is located at the cellular membrane, and is activated by binding of a ligand to the receptor’s extracellular domain. 



There are three TrkB isoforms in the CNS. 



There has been identification of NTRK1 (TrkA), NTRK2 (TrkB) and NTRK3 (TrkC) gene fusions and other oncogenic alterations in a number of tumor types. 



((Entrectinib)) a selective pan-trk receptor tyrosine kinase inhibitor (TKI) targeting gene fusions in trkA, trkB (this gene), and trkC (respectively, coded by NTRK1, NTRK2, and NTRK3 genes) 


has been approved for tumors containing these abnormalities.



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