NGF BINDING DOMAIN OF HUMAN TRKA RECEPTOR
[NTRK1_HUMAN] Defects in NTRK1 are a cause of congenital insensitivity to pain with anhidrosis (CIPA) [MIM:256800]. CIPA is characterized by a congenital insensitivity to pain, anhidrosis (absence of sweating), absence of reaction to noxious stimuli, self-mutilating behavior, and mental retardation. This rare autosomal recessive disorder is also known as congenital sensory neuropathy with anhidrosis or hereditary sensory and autonomic neuropathy type IV or familial dysautonomia type II.          Defects in NTRK1 are a cause of thyroid papillary carcinoma (TPC) [MIM:188550]. TPC is a common tumor of the thyroid that typically arises as an irregular, solid or cystic mass from otherwise normal thyroid tissue. Papillary carcinomas are malignant neoplasm characterized by the formation of numerous, irregular, finger-like projections of fibrous stroma that is covered with a surface layer of neoplastic epithelial cells. Note=Chromosomal aberrations involving NTRK1 are found in thyroid papillary carcinomas. Translocation t(1;3)(q21;q11) with TFG generates the TRKT3 (TRK-T3) transcript by fusing TFG to the 3'-end of NTRK1; a rearrangement with TPM3 generates the TRK transcript by fusing TPM3 to the 3'-end of NTRK1; an intrachromosomal rearrangement that links the protein kinase domain of NTRK1 to the 5'-end of the TPR gene forms the fusion protein TRK-T1. TRK-T1 is a 55 kDa protein reacting with antibodies against the C-terminus of the NTRK1 protein.
[NTRK1_HUMAN] Receptor tyrosine kinase involved in the development and the maturation of the central and peripheral nervous systems through regulation of proliferation, differentiation and survival of sympathetic and nervous neurons. High affinity receptor for NGF which is its primary ligand, it can also bind and be activated by NTF3/neurotrophin-3. However, NTF3 only supports axonal extension through NTRK1 but has no effect on neuron survival. Upon dimeric NGF ligand-binding, undergoes homodimerization, autophosphorylation and activation. Recruits, phosphorylates and/or activates several downstream effectors including SHC1, FRS2, SH2B1, SH2B2 and PLCG1 that regulate distinct overlapping signaling cascades driving cell survival and differentiation. Through SHC1 and FRS2 activates a GRB2-Ras-MAPK cascade that regulates cell differentiation and survival. Through PLCG1 controls NF-Kappa-B activation and the transcription of genes involved in cell survival. Through SHC1 and SH2B1 controls a Ras-PI3 kinase-AKT1 signaling cascade that is also regulating survival. In absence of ligand and activation, may promote cell death, making the survival of neurons dependent on trophic factors.      Isoform TrkA-III is resistant to NGF, constitutively activates AKT1 and NF-kappa-B and is unable to activate the Ras-MAPK signaling cascade. Antagonizes the anti-proliferative NGF-NTRK1 signaling that promotes neuronal precursors differentiation. Isoform TrkA-III promotes angiogenesis and has oncogenic activity when overexpressed.     
Publication Abstract from PubMed
The Trk receptors and their neurotrophin ligands control development and maintenance of the nervous system. The crystal structures of the ligand binding domain of TrkA, TrkB, and TrkC were solved and refined to high resolution. The domains adopt an immunoglobulin-like fold, but crystallized in all three instances as dimers with the N-terminal strand of each molecule replaced by the same strand of a symmetry-related mate. Models of the correctly folded domains could be constructed by changing the position of a single residue, and the resulting model of the binding domain of TrkA is essentially identical with the bound structure as observed in a complex with nerve growth factor. An analysis of the existing mutagenesis data for TrkA and TrkC in light of these structures reveals the structural reasons for the specificity among the Trk receptors, and explains the underpinnings of the multi-functional ligands that have been reported. The overall structure of all three domains belongs to the I-set of immunoglobulin-like domains, but shows several unusual features, such as an exposed disulfide bridge linking two neighboring strands in the same beta-sheet. For all three domains, the residues that deviate from the standard fingerprint pattern common to the I-set family fall in the region of the ligand binding site observed in the complex. Therefore, identification of these deviations in the sequences of other immunoglobulin-like domain-containing receptors may help to identify their ligand binding site even in the absence of structural or mutagenesis data.
Crystal structures of the neurotrophin-binding domain of TrkA, TrkB and TrkC.,Ultsch MH, Wiesmann C, Simmons LC, Henrich J, Yang M, Reilly D, Bass SH, de Vos AM J Mol Biol. 1999 Jul 2;290(1):149-59. PMID:10388563
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.