SASP-Secreted MMP-9 from Senescent Microglia Disrupts Nuclear-Cytoplasmic Transport Leading to TDP-43 Mislocalization and ALS Pathology
🧪 Overview
This hypothesis proposes that MMP-9 secreted by senescent microglia in the SASP drives ALS pathology through disruption of nuclear-cytoplasmic transport rather than direct proteolytic cleavage of TDP-43. MMP-9 degrades components of the nuclear pore complex, particularly nucleoporins such as NUP62 and NUP88, which are essential for maintaining the nuclear-cytoplasmic transport machinery. This proteolytic degradation compromises the nuclear import of TDP-43, leading to its aberrant cytoplasmic accumulation and subsequent aggregation. The disrupted transport also impairs the nuclear export of mRNAs that TDP-43 normally regulates, creating a feed-forward loop of RNA metabolism dysfunction. Cytoplasmic TDP-43, now separated from its nuclear targets and present at abnormally high concentrations, undergoes phase separation into pathological aggregates that sequester RNA-binding proteins and disrupt local protein synthesis. These aggregates serve as seeds for prion-like propagation to neighboring neurons through extracellular vesicles or direct cell-to-cell contact.
...🧬 Mechanism
Curated pathway from expert analysis
flowchart TD
A["MMP9 Zymogen<br/>Proenzyme Activation"]
B["Pro-MMP9 Cleavage<br/>NGAL or Other Proteases"]
C["Basement Membrane Degradation<br/>Type IV Collagen Breakdown"]
D["Blood-Brain Barrier Disruption<br/>Endothelial Tight Junctions"]
E["Chemokine Release<br/>Proinflammatory Cascade"]
F["Microglial Activation<br/>CNS Immune Response"]
G["Neuronal Process Retraction<br/>Dendritic Spine Loss"]
H["Synaptic Dysfunction<br/>Memory Circuit Impairment"]
A --> B
B --> C
C --> D
D --> E
E --> F
F --> G
G --> H
style A fill:#7b1fa2,stroke:#ce93d8,color:#ce93d8
style H fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a⚖️ Evidence
No linked papers recorded for this hypothesis yet.
🏥 Translation
🧬 3D Protein Structure — MMP9
💉 Clinical Trials
No clinical trials data linked to this hypothesis yet.
No curated ClinVar variants loaded for this hypothesis.
Run scripts/backfill_clinvar_variants.py to fetch P/LP/VUS variants.
No DepMap CRISPR Chronos data found for MMP9 → NUP62.
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
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▸Metadatasource: v1_phase_c_backfill · origin_type: gap_debate
| source | v1_phase_c_backfill |
| origin_type | gap_debate |
| _schema_version | 1 |