Structure and Function

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TRK proteins are a family of 3 transmembrane receptor tyrosine kinases (i.e. TRKA, TRKB, and TRKC) encoded by the NTRK1, NTRK2, and NTRK3 genes, respectively [1]. Structurally, TRK proteins are 140–145 kDa in size and all TRK proteins share similar structural domains including extracellular ligand binding and intracellular kinase domains [2].

In normal neuronal tissue, TRK proteins are activated by neurotrophins, and have an essential role in nervous system development and function both in adult tissues and in embryonic development as summarised in the figure below [1-3]. 

Figure 1: Normal Physiological Function of TRKs [1-3]

Figure 1: Normal Physiological Function of TRKs

TRK, tropomyosin receptor kinase.

Click here to learn more about NTRK gene fusions act as oncogenic drivers.


  1. Amatu A, Sartore-Bianchi A, Siena S. NTRK gene fusions as novel targets of cancer therapy across multiple tumour types. ESMO Open 2016; 1: e000023.
  2. Cocco E, Scaltriti M, Drilon A. NTRK fusion-positive cancers and TRK inhibitor therapy. Nat Rev Clin Oncol 2018; 15: 731-747.
  3. Vaishnavi A, Le AT, Doebele RC. TRKing down an old oncogene in a new era of targeted therapy. Cancer Discov 2015; 5: 25-34.

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Last update: 24 June 2019