Neurotrophic factors

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Neurotrophic factor
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"Neurotrophic" redirects here. Not to be confused with
Neurotropic
.

Neurotrophic factors (NTFs) are a family of

glial cell-line derived neurotrophic factor family ligands (GFLs), and (3) neuropoietic cytokines.[4] Each family has its own distinct cell signaling mechanisms, although the cellular responses elicited often do overlap.[4]

Currently, neurotrophic factors are being intensely studied for use in bioartificial nerve conduits because they are necessary

neural drug delivery systems, they are loosely immobilized such that they can be selectively released at specified times and in specified amounts.[medical citation needed
]

List of neurotrophic factors

Although more information is being discovered about neurotrophic factors, their classification is based on different cellular mechanisms and they are grouped into three main families: the

neurotrophins, the CNTF family, and GDNF family.[2][5][6]

Neurotrophins

Main article: Neurotrophin

Brain-derived neurotrophic factor

Brain-derived neurotrophic factor (BDNF) is structurally similar to NGF, NT-3, and NT-4/5,[7] and shares the TrkB receptor with NT-4.[8] The brain-derived neurotrophic factor/TrkB system promotes thymocyte survival, as studied in the thymus of mice.[8] Other experiments suggest BDNF is more important and necessary for neuronal survival than other factors.[5] However, this compensatory mechanism is still not known. Specifically, BDNF promotes survival of dorsal root ganglion neurons.[7] Even when bound to a truncated TrkB, BDNF still shows growth and developmental roles.[7] Without BDNF (homozygous (-/-)), mice do not survive past three weeks.[7]

Including development, BDNF has important regulatory roles in the development of the visual cortex, enhancing neurogenesis, and improving learning and memory.[7] Specifically, BDNF acts within the hippocampus. Studies have shown that corticosterone treatment and adrenalectomy reduces or upregulated hippocampal BDNF expression.[9] Consistent between human and animal studies, BDNF levels are decreased in those with untreated major depression.[9] However, the correlation between BDNF levels and depression is controversial.[9][10]

Nerve growth factor

immune disease, and with asthma or arthritis, amongst other conditions.[8][12]

Neurotrophin-3

Whereas neurotrophic factors within the neurotrophin family commonly have a protein tyrosine kinase receptor (Trk), Neurotrophin-3 (NT-3) has the unique receptor, TrkC.[8] In fact, the discovery of the different receptors helped differentiate scientists' understanding and classification of NT-3.[13] NT-3 does share similar properties with other members of this class, and is known to be important in neuronal survival.[13] The NT-3 protein is found within the thymus, spleen, intestinal epithelium but its role in the function of each organ is still unknown.[8]

Neurotrophin-4

Further information: Neurotrophin-4

CNTF family

The CNTF family of neurotrophic factors includes

interferons (i.e., interferon-α, -β, and -γ), and oncostatin M.[2]

Ciliary neurotrophic factor

motor neuron diseases.[16] It also has unexpected leptin-like characteristics as it causes weight loss.[14]

GDNF family

Main article: GDNF family of ligands

The GDNF family of ligands includes glial cell line-derived neurotrophic factor (GDNF), artemin, neurturin, and persephin.[2]

Glial cell line-derived neurotrophic factor

Main article: Glial cell line-derived neurotrophic factor

Glial cell line-derived neurotrophic factor (GDNF) was originally detected as survival promoter derived from a

dopaminergic (DA) neurons.[5] Specifically, studies have shown GDNF plays a protective role against MPTP toxins for DA neurons. It has also been detected in motor neurons of embryonic rats and is suggested to aid development and to reduce axotomy.[5]

Artemin

Further information: Artemin

Neurturin

Further information: Neurturin

Persephin

Further information: Persephin

Ephrins

The

eph receptors, a class of receptor tyrosine kinases;[2] the family of ephrins include ephrin A1, A2, A3, A4, A5, B1, B2, and B3
.

EGF and TGF families

The EGF and TGF families of neurotrophic factors are composed of

serine/threonine protein kinases.[2]

Other neurotrophic factors

Several other biomolecules that have identified as neurotrophic factors include:

neurotactin.[2]

References

  1. ^ a b "Neurotrophic factors". Nature Publishing Group. Retrieved 31 May 2016. Neurotrophic factors are molecules that enhance the growth and survival potential of neurons. They play important roles in both development, where they can act as guidance cues for developing neurons, and in the mature nervous system, where they are involved in neuronal survival, synaptic plasticity and the formation of long-lasting memories.
  2. ^
    ISBN 9780071481274
    . Neurotrophic factors are polypeptides or small proteins that support the growth, differentiation, and survival of neurons. They produce their effects by activation of tyrosine kinases.
  3. PMID 22166417
    . As will be discussed below, exercise stimulates the expression of several neurotrophic factors (NTFs).
  4. ^
    S2CID 21122249
    .
  5. ^
    S2CID 29876053
    .
  6. PMID 18629541
    .
  7. ^
    PMID 15518235
    .
  8. ^
    PMID 12892403
    .
  9. ^
    PMID 21253405
    .
  10. PMID 17700574
    .
  11. ^
    PMID 10811872
    .
  12. ^
    PMID 24585880
    .
  13. ^
    PMID 8789936
    .
  14. ^
    PMID 11259650
    .
  15. PMID 8050491
    .
  16. S2CID 4369702
    .
  17. S2CID 32315320
    .

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