TrkC
Encyclopedia
NT-3 growth factor receptor also known as neurotrophic tyrosine kinase receptor type 3 or TrkC tyrosine kinase or Trk-C receptor is a protein
that in humans is encoded by the NTRK3 gene
.
TrkC is the high affinity catalytic receptor
for the neurotrophin
NT-3 (neurotrophin-3
). As such, TrkC mediates the multiple effects of this neurotrophic factor, which includes neuronal differentiation and survival.
The TrkC receptor is part of the large family of receptor tyrosine kinases. A "tyrosine kinase
" is an enzyme which is capable of adding a phosphate group to the certain tyrosines on target proteins, or "substrates". A receptor tyrosine kinase
is a "tyrosine kinase" which is located at the cellular membrane, and is activated by binding of a ligand via its extracellular domain. Other example of tyrosine kinase receptors include the insulin receptor
, the IGF-1 receptor, the MuSK protein
receptor, the Vascular Endothelial Growth Factor
(or VEGF
) receptor, etc. The "substrate" proteins which are phosphorylated by TrkC include PI3 kinase.
and TrkB
. Also, there are other neurotrophic factors structurally related to NT-3: NGF (for Nerve Growth Factor
), BDNF (for Brain Derived Neurotrophic Factor) and NT-4 (for Neurotrophin-4). While TrkB mediates the effects of BDNF, NT-4 and 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.
"). As opposed to TrkC, the LNGFR plays a somewhat less clear role in 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.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
that in humans is encoded by the NTRK3 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
TrkC is the high affinity catalytic receptor
Catalytic receptor
A Catalytic receptor is an integral membrane protein possessing both enzymatic catalytic and receptor functions.The following is a list of the five major families of catalytic receptors:...
for the neurotrophin
Neurotrophin
Neurotrophins are a family of proteins that induce the survival, development, and function of neurons.They belong to a class of growth factors, secreted proteins that are capable of signaling particular cells to survive, differentiate, or grow. Growth factors such as neurotrophins that promote the...
NT-3 (neurotrophin-3
Neurotrophin-3
Neurotrophin-3 is a protein that in humans is encoded by the NTF3 gene.The protein encoded by this gene, NT-3, is a neurotrophic factor in the NGF family of neurotrophins...
). As such, TrkC mediates the multiple effects of this neurotrophic factor, which includes neuronal differentiation and survival.
The TrkC receptor is part of the large family of receptor tyrosine kinases. A "tyrosine kinase
Kinase
In chemistry and biochemistry, a kinase is a type of enzyme that transfers phosphate groups from high-energy donor molecules, such as ATP, to specific substrates, a process referred to as phosphorylation. Kinases are part of the larger family of phosphotransferases...
" is an enzyme which is capable of adding a phosphate group to the certain tyrosines on target proteins, or "substrates". A receptor tyrosine kinase
Receptor tyrosine kinase
Receptor tyrosine kinases s are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinase proteins....
is a "tyrosine kinase" which is located at the cellular membrane, and is activated by binding of a ligand via its extracellular domain. Other example of tyrosine kinase receptors include the insulin receptor
Insulin receptor
In molecular biology, the insulin receptor is a transmembrane receptor that is activated by insulin. It belongs to the large class of tyrosine kinase receptors....
, the IGF-1 receptor, the MuSK protein
MuSK protein
MuSK is a receptor tyrosine kinase required for the formation of the neuromuscular junction. It is activated by a nerve-derived proteoglycan called agrin.-MuSK is required for formation of the Neuromuscular Junction:...
receptor, the Vascular Endothelial Growth Factor
Vascular endothelial growth factor
Vascular endothelial growth factor is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. It is part of the system that restores the oxygen supply to tissues when blood circulation is inadequate....
(or VEGF
Vascular endothelial growth factor
Vascular endothelial growth factor is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. It is part of the system that restores the oxygen supply to tissues when blood circulation is inadequate....
) receptor, etc. The "substrate" proteins which are phosphorylated by TrkC include PI3 kinase.
Family Members
TrkC is part of a sub-family of protein kinases which includes TrkATrkA
High affinity nerve growth factor receptor also known as neurotrophic tyrosine kinase receptor type 1 or TRK1-transforming tyrosine kinase protein or Trk-A is a protein that in humans is encoded by the NTRK1 gene....
and TrkB
TrkB
TrkB receptor also known as TrkB tyrosine kinase or BDNF/NT-3 growth factors receptor or neurotrophic tyrosine kinase, receptor, type 2 is a protein that in humans is encoded by the NTRK2 gene.-Function:...
. Also, there are other neurotrophic factors structurally related to NT-3: NGF (for Nerve Growth Factor
Nerve growth factor
Nerve growth factor is a small secreted protein that is important for the growth, maintenance, and survival of certain target neurons . It also functions as a signaling molecule. It is perhaps the prototypical growth factor, in that it is one of the first to be described...
), BDNF (for Brain Derived Neurotrophic Factor) and NT-4 (for Neurotrophin-4). While TrkB mediates the effects of BDNF, NT-4 and 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 NT-3 receptor family besides the Trks (TrkC & TrkB), called the "LNGFR" (for "low affinity nerve growth factor receptorLow Affinity Nerve Growth Factor Receptor
The Low-Affinity Nerve Growth Factor Receptor is one of the two receptor types for the neurotrophins, a family of protein growth factors that stimulate neuronal cells to survive and differentiate...
"). As opposed to TrkC, the LNGFR plays a somewhat less clear role in 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.