Claudin-5 is the most abundant tight junction protein in brain endothelial cells and is specifically degraded during early neurodegeneration. Proteolytic cleavage by MMPs and γ-secretase generates circulating C-terminal fragments detectable in plasma. Detection of these fragments specifically indicates paracellular BBB leakage, distinguishing it from transcytosis-mediated permeability changes. This hypothesis has therapeutic potential through tight junction stabilization, but requires de novo assay development and fragment identification before clinical validation can proceed.
Curated pathway from expert analysis
flowchart TD A["Neurodegeneration"] --> B["MMPs Activation"] A --> C["Gamma-Secretase Activation"] B --> D["Claudin-5 Cleavage"] C --> D D --> E["C-terminal Fragments"] E --> F["Plasma Detection"] F --> G["Paracellular BBB Breakdown"] G --> H["Cognitive Decline"] G --> I["Neuroinflammation"] A --> J["Transcytosis Upregulation"] J --> K["Transport Dysfunction"] K --> H K --> I F -->|" Distinguishes "|K L["Minocycline or PPAR-gamma Agonists"] --> M["Tight Junction Stabilization"] M --> N["Claudin-5 Protection"] N --> D N -->|" Prevents "|O["BBB Leakage Reduction"]
No linked papers recorded for this hypothesis yet.
No curated PDB or AlphaFold mapping for CLDN5 yet. Search RCSB →
Median TPM across 13 brain regions for CLDN5 from GTEx v10.
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 CLDN5.
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
No resource usage or linked notebooks recorded for this hypothesis yet.
| Prediction | Predicted | Observed | Status | Conf |
|---|---|---|---|---|
| If plasma claudin-5 proteolytic fragments specifically distinguish paracellular BBB breakdown from transcytosis, then fragment patterns will differ between paracellular leakage (high full-length CLDN5 | In patients with confirmed BBB dysfunction (n≥80), western blot analysis shows two distinct fragment patterns: Pattern A (paracellular: full-length CLDN5 + N-te | — no observation — | pending | 0.77 |
| If CLDN5 fragment elevation specifically reflects paracellular BBB disruption, then plasma CLDN5 fragments will be absent or low in pure transcytosis models (e.g., diabetic patients without BBB imagin | In pure transcytosis model (type 2 DM without MRI BBB changes, n≥30), plasma CLDN5 fragments are within normal range (<100 pg/mL); in paracellular disruption (T | — no observation — | pending | 0.72 |