Tdp 43 Proteinopathy In Amyotrophic Lateral Sclerosis is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
TDP-43 (TAR DNA-binding protein 43) is a nuclear RNA/DNA-binding protein that plays critical roles in RNA metabolism, including transcription, splicing, transport, and translation. In approximately 95% of amyotrophic lateral sclerosis (ALS) cases and 50% of frontotemporal dementia (FTD) cases, TDP-43 accumulates in cytoplasmic inclusions, forming the hallmark pathological feature known as TDP-43 proteinopathy 1. This page describes the molecular mechanisms underlying TDP-43 pathology in ALS and its relationship to disease pathogenesis.
TDP-43 is encoded by the TARDBP gene (chromosome 1p36.22) and consists of 414 amino acids with multiple functional domains 2:
- N-terminal domain: Nuclear localization signal (NLS) and DNA-binding domain
- RNA recognition motif (RRM) 1 & 2: Bind to single-stranded DNA/RNA
- C-terminal domain: Prion-like glycine-rich region for protein interactions
TDP-43 regulates:
- Alternative splicing of pre-mRNAs, including CFTR, ApoER2, and neuronal transcripts
- RNA stability by binding to 3' UTRs
- Transport of mRNAs along axons via interaction with transport granules
- Translation regulation through ribosomal protein interactions
Under physiological conditions, TDP-43 predominantly localizes to the nucleus where it performs its RNA processing functions. It shuttles between nucleus and cytoplasm, with cytoplasmic presence increasing during stress 3.
The earliest pathological change in ALS is the mislocalization of TDP-43 from the nucleus to the cytoplasm 4. This occurs due to:
- Nuclear export dysfunction: Impaired nuclear import/export balance
- Post-translational modifications: Hyperphosphorylation, ubiquitination, SUMOylation
- Proteolytic cleavage: Generation of C-terminal fragments
- Aggregation: Loss of nuclear function and toxic gain-of-function
Cytoplasmic TDP-43 aggregates take multiple forms:
- Skein-like inclusions: Filamentous structures
- Round inclusions: Compact aggregates
- Neuronal cytoplasmic inclusions (NCIs): In neuronal cell bodies
- Neuronal intranuclear inclusions (NIIs): In some subtypes
These inclusions are hyperphosphorylated at Ser409/410 and often ubiquitinated 5.
Cytoplasmic mislocalization leads to:
- Nuclear depletion: Loss of TDP-43 in the nucleus
- RNA splicing dysregulation: Aberrant splicing of target transcripts
- Nuclear envelope abnormalities: Disrupted nuclear integrity
- DNA damage accumulation: Impaired DNA repair mechanisms
TDP-43 pathology causes widespread splicing alterations 6:
| Gene |
Normal Function |
ALS Splicing Change |
| STMN2 |
Axon growth |
Exon 2a inclusion |
| UNC13A |
Synaptic transmission |
Cryptic exon inclusion |
| TFG |
ER stress response |
Intron retention |
| KCNMA1 |
Potassium channel |
Exon skipping |
TDP-43 interacts with stress granules (SGs) — cytoplasmic RNA-protein assemblies formed during cellular stress 7:
- TDP-43 localizes to SGs under stress conditions
- Prolonged SG association leads to irreversible aggregation
- SG-mediated sequestration disrupts RNA metabolism
- Stress granule dysfunction propagates pathology
Over 50 mutations in TARDBP are linked to familial and sporadic ALS 8, predominantly located in the C-terminal glycine-rich domain:
- G298S, A315T, M337V, Q343R, N345K, R361S, Y374X
These mutations:
- Enhance cytoplasmic mislocalization
- Increase aggregation propensity
- Reduce RNA-binding affinity in some cases
The most common genetic cause of ALS/FTD is hexanucleotide repeat expansion in C9orf72 9. TDP-43 pathology develops in approximately 90% of C9orf72-ALS cases through:
- DPR toxicity: Dipeptide repeat proteins from expanded repeats
- RNA foci sequestration: Toxic RNA foci trap TDP-43
- Nucleocytoplasmic transport defects: Impaired nuclear import
Motor neurons are particularly vulnerable to TDP-43 pathology due to:
- Long axons: High transport requirements
- High metabolic demand: Increased oxidative stress
- Large cell size: Challenging protein homeostasis
- Specialized RNA granules: Unique transport mechanisms
Non-neuronal cells contribute to TDP-43 propagation 10:
- Astrocytes: Release of toxic factors, impaired glutamate uptake
- Microglia: Neuroinflammation, cytokine release
- Oligodendrocytes: Demyelination, metabolic support loss
| Strategy |
Approach |
Status |
| Reduce mislocalization |
Nuclear import enhancers |
Preclinical |
| Inhibit phosphorylation |
Kinase inhibitors |
Preclinical |
| Promote autophagy |
mTOR inhibition, trehalose |
Clinical trials |
| Antisense oligonucleotides |
TARDBP ASOs |
Phase 1/2 trials |
| RNA granule modulators |
SG disassembly promoters |
Preclinical |
TDP-43 fragments in cerebrospinal fluid (CSF) and blood serve as biomarkers for disease progression and therapeutic response 11.
- mechanisms/als-c9orf72-pathway: C9orf72 hexanucleotide expansion and TDP-43
- mechanisms/als-superoxide-dismutase-pathway: SOD1 aggregation in ALS
- diseases/als-ftd-spectrum: ALS-FTD Spectrum disorders
- genes/tardbp: TARDBP gene page
- proteins/tardbp-protein: TDP-43 protein page
- entities/stress-granules: Stress granules in neurodegeneration
The study of Tdp 43 Proteinopathy In Amyotrophic Lateral Sclerosis 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.
- Neumann M, et al. (2006). Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science. 314(5796):130-133. PMID:17023659
- Buratti E, Baralle M. (2006). TDP-43: new aspects of auto-regulation and co-transcriptional RNA processing. Cell Mol Life Sci. 63(7-8):797-808. PMID:16465448
- Ayala YM, et al. (2008). Nuclear cytoplasmic trafficking of TDP-43 is regulated by stress granules but not by ALS-causing mutations. Mol Cell Biol. 28(7):2321-2331. PMID:18216106
- Giordana MT, et al. (2010). TDP-43 redistribution is an early event in sporadic amyotrophic lateral sclerosis. Brain Pathol. 20(2):351-360. PMID:18624795
- Hasegawa M, et al. (2008). Phosphorylated TDP-43 in frontotemporal lobar degeneration and ALS. J Neuropathol Exp Neurol. 67(6):555-564. PMID:18520774
- Tollervey JR, et al. (2011). Characterizing the RNA targets and position-dependent splicing regulation by TDP-43. Nat Neurosci. 14(4):452-458. PMID:21358640
- Liu-Yesucevitz L, et al. (2010). Altered RNA metabolism and ALS. Ann Neurol. 67(1):110-117. PMID:20186856
- Lattante S, et al. (2015). TARDBP mutations in ALS and FTD: pathogenesis and therapeutic targets. J Mol Neurosci. 55(2):369-379. PMID:25280650
- DeJesus-Hernandez M, et al. (2011). Expanded GGGGCC hexanucleotide repeat in noncoding region of C9ORF72 causes chromosome 9p-linked FTD and ALS. Neuron. 72(2):245-256. PMID:21944778
- Ilieva H, et al. (2009). Non-cell autonomous toxicity in neurodegenerative disorders: ALS and beyond. J Cell Biol. 187(6):761-772. PMID:19948480
- Feneberg E, et al. (2022). TDP-43 and neurofilament markers in ALS. Nat Rev Neurol. 18(1):9-22. PMID:34795464
🔴 Low Confidence
| Dimension |
Score |
| Supporting Studies |
11 references |
| Replication |
0% |
| Effect Sizes |
25% |
| Contradicting Evidence |
0% |
| Mechanistic Completeness |
50% |
Overall Confidence: 33%