Trk receptor

							Trk receptor
POONEH HESHMATI MD

Trk receptors are a family of tyrosine kinases that regulates synaptic strength and plasticity in the mammalian nervous system.

Trk receptor types and corresponding ligands
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The three most common types of trk receptors are trkA, trkB, and trkC.

TrkA
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TrkA has the highest affinity to the binding nerve growth factor (NGF).

TrkB

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TrkB has the highest affinity to the binding brain-derived neurotrophic factor (BDNF) and NT-4.

TrkC
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TrkC is ordinarily activated by binding with NT3 and has little activation by other ligands.

Ligands of trk receptors
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The common ligands of trk receptors are neurotrophins, a family of growth factors critical to the functioning of the nervous system.

(Found only in fish)

Activation pathway
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Trk receptors dimerize in response to ligand, as do other tyrosine kinase receptors. These dimers phosphorylate each other and enhance catalytic activity of the kinase.

Trk receptor signaling
When a neurotrophin binds to a trk receptor, the kinase domain is activated resulting in autophosphorylation.

Autophoshorylation results in further activation of the kinase domain, leading to activation of three potential signaling cascades:
MAPK PI3K PLC-g

Axonal Regeneration
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During PNS regeneration, Schwann cells secrete a variety of neurotrophic and neurotropic factors to support axonal regrowth . Regenerating neuronal growth cones have been shown to express many correspondent receptors.

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Understanding how these cell surface receptors are regulated in response to injury may lead to know more about PNS regeneration .