TrkC Protein — Tropomyosin Receptor Kinase C
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<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">TrkC Protein</th></tr>
<tr><td><strong>Protein Name</strong></td><td>Tropomyosin Receptor Kinase C</td></tr>
<tr><td><strong>Gene</strong></td><td>[NTRK3](/genes/ntrk3)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q16620](https://www.uniprot.org/uniprot/Q16620)</td></tr>
<tr><td><strong>PDB ID</strong></td><td>1HCF, 2ITM</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>145 kDa (full-length)</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Plasma membrane, endosomes</td></tr>
<tr><td><strong>Protein Family</strong></td><td>Trk receptor tyrosine kinase family</td></tr>
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<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
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Introduction
Tropomyosin receptor kinase C (TrkC), encoded by the NTRK3 gene, is a member of the Trk (tropomyosin receptor kinase) family of receptor tyrosine kinases[@barbacid1994]. TrkC serves as the high-affinity receptor for neurotrophin-3 (NT-3), a member of the neurotrophin family of growth factors that also includes nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-4/5 (NT-4)[@lessmann2003]. While TrkA and TrkB have been extensively studied in the context of neurodegeneration, TrkC has received less attention but represents an emerging area of research with significant therapeutic implications for neurodegenerative diseases.
Overview
Mermaid diagram (expand to render)
TrkC is primarily expressed in proprioceptive [neurons](/entities/neurons), motor neurons, and certain populations of hippocampal and cortical neurons. Unlike TrkA (which preferentially binds NGF) and TrkB (which preferentially binds BDNF), TrkC has unique ligand specificity for NT-3[@snider1994]. This receptor plays critical roles in neuronal development, survival, and synaptic plasticity, and evidence suggests it may have neuroprotective properties in certain neurodegenerative conditions.
Background
The Trk family of receptor tyrosine kinases was discovered in the 1980s as oncogenic fusion proteins in certain cancers, leading to the identification of their normal roles in nervous system development. TrkC was identified as the third member of this family, with distinct expression patterns and ligand specificity compared to TrkA and TrkB[@patapoutian2001]. Research has shown that TrkC signaling follows both classical neurotrophin signaling pathways and unique mechanisms that are still being elucidated.
The NTRK3 gene, located on chromosome 15q25.3 in humans, encodes multiple isoforms of TrkC through alternative splicing. The full-length isoform (TrkC.FL) contains a functional tyrosine kinase domain, while truncated isoforms (TrkC.TK-) lack the kinase domain and may function as dominant-negative regulators or independent signaling molecules[@menn1998].
Structure
TrkC shares structural features with other Trk receptors:
Extracellular Domain
- Leucine-rich repeats (LRRs): Mediate initial ligand binding specificity
- Cysteine-rich domains: Stabilize ligand-receptor interactions
- Ig-like C2-type domains: Provide additional ligand interaction surfaces
Transmembrane Domain
- Single α-helical transmembrane helix connecting extracellular and intracellular domains
Intracellular Domain
- Tyrosine kinase domain: Catalytic activity for downstream signaling
- Multiple phosphorylation sites: Regulate signaling intensity and duration
- Docking sites: For adaptor proteins (Shc, PLC-γ)
TrkC is unique among Trk receptors in that some splice isoforms lack the kinase domain entirely, producing truncated receptors that may modulate signaling through the full-length receptor[@sato1999].
Normal Function
TrkC is the primary receptor for neurotrophin-3 (NT-3)[@liu2012]:
Motor Neuron Survival: NT-3/TrkC signaling is critical for motor neuron development, maintenance, and regeneration following injury[@brunet2019]
Synaptic Plasticity: TrkC regulates hippocampal synaptic function, including [long-term potentiation](/mechanisms/long-term-potentiation) (LTP) and synaptic vesicle release[@gomez2019]
Proprioception: Essential for sensory neuron function, particularly in proprioceptive neurons that detect body position[@ernfors1994]
Learning and Memory: Hippocampal TrkC supports cognitive function through modulation of synaptic plasticity and neuronal survival[@minichiello1999]
Neuronal Differentiation: NT-3/TrkC signaling promotes neuronal differentiation during developmentRole in Disease
Alzheimer's Disease
- Reduced TrkC expression observed in [hippocampus](/brain-regions/hippocampus) of AD patients[@salehi1998]
- NT-3/TrkC signaling has neuroprotective effects against amyloid-β toxicity[@zhang2017]
- Potential therapeutic target for cognitive decline
- May modulate [tau](/proteins/tau) phosphorylation and aggregation
Parkinson's Disease
- TrkC expressed in dopaminergic neurons of substantia nigra
- NT-3 may protect against 6-OHDA and MPTP toxicity
- Therapeutic potential for motor symptoms
Amyotrophic Lateral Sclerosis (ALS)
- TrkC mutations linked to rare familial ALS cases
- Motor neuron survival supported by NT-3/TrkC signaling
- Gene therapy approaches using NT-3 under investigation
Neurodevelopmental Disorders
- Mutations in NTRK3 linked to neurodevelopmental syndromes
- Impaired NT-3/TrkC signaling affects neuronal development
- Associated with epilepsy and cognitive impairment
Therapeutic Implications
TrkC represents a promising therapeutic target:
Small Molecule Agonists: Development of TrkC-selective small molecules that can cross the [blood-brain barrier](/entities/blood-brain-barrier)
NT-3 Delivery: Protein or gene therapy approaches to deliver NT-3 to the CNS
Allosteric Modulators: Positive allosteric modulators to enhance TrkC signaling
Cell-Based Therapy: Transplantation of cells engineered to express NT-3See Also
- [NTRK3 Gene](/genes/ntrk3)
- [TrkA Protein](/proteins/trka-protein)
- [TrkB Protein](/proteins/trkb-protein)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Neurotrophic Factors](/mechanisms/neurotrophic-factors)
External Links
- [UniProt: trkc](https://www.uniprot.org/)
- [PubMed: trkc](https://pubmed.ncbi.nlm.nih.gov/?term=trkc+neurodegeneration)
References
[Unknown, Barbacid, M. (1994). The Trk family of neurotrophin receptors. Journal of Neurobiology, 25(11), 1386-1403 (1994)](https://pubmed.ncbi.nlm.nih.gov/7924005/)
[Lessmann, V. et al., (2003). Neurotrophin secretion: current facts and future prospects. Progress in Neurobiology, 69(5), 341-374 (2003)](https://pubmed.ncbi.nlm.nih.gov/12749708/)
Unknown, Snider, W.D. (1994). Functions of the neurotrophins during nervous system development: what the knockouts are teaching us. Cell, 77(5), 627-638 (1994)
[Unknown, Patapoutian, A. & Reichardt, L.F. (2001). Trk receptors: mediators of neurotrophin action. Current Opinion in Neurobiology, 11(3), 272-280 (2001)](https://pubmed.ncbi.nlm.nih.gov/11399424/)
[Menn, B. et al., (1998). Alternative splicing of the TrkC gene messages in the rodent nervous system. Journal of Neuroscience Research, 51(3), 349-363 (1998)](https://pubmed.ncbi.nlm.nih.gov/9486770/)
Sato, M. et al., (1999). TrkC variant in the kinase domain: another mechanism for truncated receptors. FEBS Letters, 447(2-3), 119-124 (1999)
[Liu, X. et al., (2012). The neurotrophin receptor TrkC: a potential therapeutic target in Parkinson's disease. Experimental Neurology, 236, 267-273 (2012)](https://pubmed.ncbi.nlm.nih.gov/22579443/)
Brunet, N. et al., (2019). Neurotrophin-3 promotes motor neuron survival through TrkC. Molecular Neurobiology, 56(8), 5646-5658 (2019)
Unknown, Gomez, J.L. & Lu, B. (2019). Neurotrophin-3 and TrkC in synaptic plasticity and function. Brain Research, 1727, 146556 (2019)
Ernfors, P. et al., (1994). TrkC is essential for innervation of specific muscle spindle and Golgi tendon organ populations. Neuron, 13(2), 331-342 (1994)
Minichiello, L. et al., (1999). Mechanism of TrkB-mediated hippocampal long-term potentiation. Neuron, 23(2), 233-245 (1999)
Salehi, A. et al., (1998). Decreased TrkA and increased p75(NTR) in the hippocampus of Alzheimer's disease patients. Neuroscience, 86(4), 1125-1138 (1998)
Zhang, Y. et al., (2017). Neurotrophin-3 provides neuroprotection via TrkC in Alzheimer's disease. Journal of Alzheimer's Disease, 58(3), 797-810 (2017)Pathway Diagram
The following diagram shows the key molecular relationships involving TrkC Protein discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)