| Brain-Derived Neurotrophic Factor (BDNF) | |
|---|---|
| Gene | [BDNF](/genes/bdnf) |
| UniProt | P23560 |
| PDB | 1BND, 1B8M |
| Mol. Weight | 13.5 kDa (mature), 27.8 kDa (pro-BDNF) |
| Localization | Secreted, Synaptic vesicles |
| Family | Neurotrophin family |
| Diseases | [Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), [Depression](/diseases/depression) |
Brain-Derived Neurotrophic Factor (BDNF) is a critical neurotrophin encoded by the BDNF gene that supports the survival, growth, and plasticity of neurons throughout the central and peripheral nervous systems[1]. This secreted protein belongs to the neurotrophin family and exists in two forms: pro-BDNF (27.8 kDa) and mature BDNF (13.5 kDa), which have distinct biological activities and receptor specificities[2]. BDNF is widely expressed in the brain, with particularly high levels in the hippocampus, cortex, and basal forebrain, regions critical for learning, memory, and mood regulation[3].
BDNF plays essential roles in neurodevelopment and adult brain function, and its dysregulation has been implicated in numerous neurological and psychiatric disorders including Alzheimer's disease, Parkinson's disease, depression, and anxiety[4].
BDNF is initially synthesized as a precursor molecule (pro-BDNF) that can be cleaved to generate mature BDNF:
| Form | Molecular Weight | Receptor | Function |
|---|---|---|---|
| Pro-BDNF | 27.8 kDa | p75^NTR | Pro-apoptotic, synaptic depression |
| Mature BDNF | 13.5 kDa | TrkB | Pro-survival, synaptic plasticity |
The balance between pro-BDNF and mature BDNF is critical for proper neuronal function and is regulated by proteolytic cleavage via plasmin and matrix metalloproteinases (MMPs)[2:1].
BDNF signals through two classes of receptors:
TrkB (Tropomyosin receptor kinase B)
p75^NTR (p75 neurotrophin receptor)
During development, BDNF is essential for:
In the adult brain, BDNF supports:
BDNF expression is highly activity-dependent:
BDNF is intimately involved in AD pathogenesis:
Therapeutic approaches include BDNF delivery and TrkB agonists[9].
In PD, BDNF supports dopaminergic neuron survival:
BDNF is a key mediator of antidepressant efficacy:
| Intervention | BDNF Effect | Evidence |
|---|---|---|
| Exercise | Increases | Strong |
| Caloric restriction | Increases | Moderate |
| Sleep | Increases | Moderate |
| Meditation | Increases | Emerging |
BDNF structure has been characterized:
| Feature | Details |
|---|---|
| Structure | Homodimer |
| PDB entries | 1BND, 1B8M, 3MJG |
| Crystallization | Diffraction to 1.5 Å |
| Fold | Cystine knot (NTR family) |
The mature BDNF forms a homodimer that binds two TrkB receptors, triggering dimerization and autophosphorylation[2:2].
The most studied BDNF polymorphism:
Brain Derived Neurotrophic Factor (Bdnf) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes. [1:3] [1:4]
Brain-Derived Neurotrophic Factor (BDNF) is a member of the neurotrophin family of growth factors that plays essential roles in neuronal survival, differentiation, synaptic plasticity, and cognitive function. BDNF is the most abundant neurotrophin in the adult brain, with particularly high expression in the hippocampus, cerebral [cortex, and basal-ganglia . In the context of [neurodegenerative diseases, BDNF has emerged as a central mediator linking synaptic dysfunction, neuronal loss, and cognitive decline. [2:4] [2:5]
Reduced BDNF expression has been consistently documented in alzheimers, parkinsons, huntington-pathway, and als, making it both a promising biomarker and a therapeutic target for neurodegenerative conditions . The dual signaling system of mature BDNF (via TrkB receptors promoting survival) and proBDNF (via p75NTR promoting [apoptosis) provides a nuanced framework for understanding how neurotrophic signaling goes awry in neurodegeneration. [3:2]
The human BDNF gene is located on chromosome 11p14.1 and has a complex structure with multiple promoters and at least nine 5' non-coding exons, each spliced to a common 3' coding exon. This architecture allows tissue-specific and activity-dependent regulation of BDNF expression. [4:2]
BDNF is initially synthesized as a precursor protein (preproBDNF, ~32 kDa), which is cleaved to proBDNF (~28 kDa) in the endoplasmic reticulum. ProBDNF can be further processed to mature BDNF (~14 kDa) by intracellular furin or proprotein convertases, or extracellularly by plasmin and matrix metalloproteinases. Critically, proBDNF and mature BDNF have distinct and often opposing biological activities : [5:2]
This yin-yang relationship between mBDNF and proBDNF is central to understanding BDNF's role in both normal brain function and neurodegeneration. [6:1]
Mature BDNF binds with high affinity to the tropomyosin receptor kinase B (TrkB, also known as NTRK2), triggering receptor homodimerization and autophosphorylation of intracellular tyrosine residues. This activates three major downstream signaling cascades : [7:1]
ProBDNF preferentially binds to the p75 neurotrophin receptor (p75NTR), often in complex with the co-receptor sortilin. This activates : [8:1]
The balance between TrkB and p75NTR signaling is critical: in neurodegeneration, reduced mBDNF levels and increased proBDNF may shift this balance toward pro-apoptotic signaling.
The Val66Met single nucleotide polymorphism (rs6265) in the BDNF gene is the most extensively studied genetic variant, present in approximately 20-30% of the population (higher frequency in Asian populations). The methionine substitution at codon 66 in the prodomain :
BDNF is profoundly reduced in alzheimers, particularly in the hippocampus and temporal cortex—regions most affected by AD pathology. The mechanisms linking BDNF deficiency to AD include :
amyloid-beta toxicity: amyloid-beta oligomers reduce BDNF expression and disrupt TrkB signaling, creating a feedforward cycle of synaptic-dysfunction
tau-protein(/proteins/tau pathology]: BDNF depletion accelerates tau] hyperphosphorylation] through reduced PI3K/Akt signaling and subsequent gsk3-beta activation
Cholinergic degeneration: BDNF is a key survival factor for cholinergic neurons of the nucleus-basalis-of-meynert
neuroinflammation: BDNF deficiency exacerbates microglial/cell-types/microglia:
Reduced BDNF mRNA and protein levels are found in the substantia nigra of PD patients
Downregulation of TrkB signaling contributes to dopaminergic neuron vulnerability
[alpha-synuclein aggregates impair BDNF-TrkB signaling
BDNF supports nigrostriatal dopaminergic neuron survival, and its loss accelerates neurodegeneration
The mutant huntingtin protein] in huntington-pathway directly impairs BDNF transcription and axonal transport :
In als, BDNF levels are altered in motor neurons and surrounding astrocytes. While BDNF supports motor neuron survival in vitro, clinical trials of BDNF delivery in ALS patients have produced disappointing results, possibly due to difficulties achieving adequate concentrations at motor neuron cell bodies .
Several approaches to boosting endogenous BDNF production are under investigation :
Serum and plasma BDNF levels have been investigated as potential biomarkers for neurodegenerative diseases. Key findings include :
The study of Brain Derived Neurotrophic Factor (Bdnf) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying [mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
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Egan MF, Kojima M, Callicott JH, Goldberg TE, Kolachana BS, Bertolino A, Zaitsev E, Gold B, Goldman D, Dean M, Lu B, Weinberger DR. [The BDNF val66met polymorphism affects activity-dependent secretion of BDNF and human memory and hippocampal function](https://doi.org/10.1016/S0092-8674(03). Cell. 2003. ↩︎
Monteggia LM, Barrot M, Powell CM, Berton O, Galanis V, Gemelli T, Meuth S, Nagy A, Greene RW, Nestler EJ. Essential role for brain-derived neurotrophic factor in mood disorders. Proceedings of the National Academy of Sciences. 2004. ↩︎