Tropomyosin receptor kinase C

Tropomyosin receptor kinase C (TrkC), also known as NT-3 growth factor receptor, neurotrophic tyrosine kinase receptor type 3, or TrkC tyrosine kinase is a is_associated_with::protein that in humans is encoded by the NTRK3 is_associated_with::gene.

TrkC is the high affinity is_associated_with::catalytic receptor for the is_associated_with::neurotrophin is_associated_with::NT-3 (is_associated_with::neurotrophin-3). As such, TrkC mediates the multiple effects of this is_associated_with::neurotrophic factor, which includes neuronal differentiation and survival.

The TrkC receptor is part of the large family of is_associated_with::receptor tyrosine kinases. A "tyrosine is_associated_with::kinase" is an enzyme which is capable of adding a phosphate group to the certain tyrosines on target proteins, or "substrates". A is_associated_with::receptor tyrosine kinase is a "tyrosine kinase" which is located at the cellular membrane, and is activated by binding of a is_associated_with::ligand via its extracellular domain. Other example of tyrosine kinase receptors include the is_associated_with::insulin receptor, the IGF-1 receptor, the is_associated_with::MuSK protein receptor, the Vascular Endothelial Growth Factor (or VEGF) receptor, etc. The "substrate" proteins which are phosphorylated by TrkC include is_associated_with::PI3 kinase.

Family Members
TrkC is part of a sub-family of protein kinases which includes is_associated_with::TrkA and is_associated_with::TrkB. Also, there are other neurotrophic factors structurally related to is_associated_with::NT-3: NGF (for is_associated_with::Nerve Growth Factor), is_associated_with::BDNF (for Brain Derived Neurotrophic Factor) and NT-4 (for Neurotrophin-4). While TrkB mediates the effects of BDNF, NT-4 and is_associated_with::NT-3, TrkA is bound and thereby activated only by NGF. Further, TrkC binds and is activated only by NT-3.

TrkB binds BDNF and NT-4 more strongly than it binds NT-3. TrkC binds NT-3 more strongly than TrkB does.

The LNGFR
There is one other is_associated_with::NT-3 receptor family besides the Trks (TrkC & TrkB), called the "is_associated_with::LNGFR" (for "is_associated_with::low affinity nerve growth factor receptor"). As opposed to TrkC, the LNGFR plays a somewhat less clear role in is_associated_with::NT-3 biology. Some researchers have shown the LNGFR binds and serves as a "sink" for neurotrophins. Cells which express both the LNGFR and the Trk receptors might therefore have a greater activity - since they have a higher "microconcentration" of the neurotrophin. It has also been shown, however, that the LNGFR may signal a cell to die via apoptosis - so therefore cells expressing the LNGFR in the absence of Trk receptors may die rather than live in the presence of a neurotrophin.