Neuronal mitochondrial dynamics are uniquely governed by the opposing activities of fission (DRP1-mediated) and fusion (MFN1/MFN2-mediated) proteins, with the balance critically determining mitochondrial morphology, distribution, and functional quality. This hypothesis proposes that in neurodegeneration-associated senescence, chronic DRP1 S616 hyperphosphorylation (driven by CDK5 and PKCδ activation) shifts the fission-fusion balance toward excessive fragmentation, producing small, depolarized mitochondria that cannot efficiently meet neuronal ATP demands. Simultaneously, MFN2 is downregulated at both transcriptional and protein levels through p53-mediated repression of the MFN2 promoter, further impairing fusion capacity. The resulting mitochondrial fragmentation triggers a senescence-associated metabolic phenotype characterized by reduced oxidative phosphorylation (Complex I activity <40% of controls), compensatory glycolytic shift (2-fold increase in lactate production), and ROS overproduction (mtROS levels 3-4× above baseline).
...Curated pathway from expert analysis
flowchart TD
A["CDK5 and PKCdelta Activation<br/>Senescence-Associated Kinase Surge"]
B["DRP1 Ser616 Hyperphosphorylation<br/>Fission Machinery Overactivated"]
C["p53 Stabilization<br/>MFN2 Promoter Repression"]
D["MFN2 Protein Downregulated 60 percent<br/>Fusion Capacity Impaired"]
E["Mitochondrial Fragmentation<br/>Small Depolarized Mitochondria"]
F["Complex I Activity Below 40 percent<br/>Glycolytic Shift and ROS Overproduction"]
G["Parkin Recruitment Fails<br/>Impaired Mitophagic Elimination"]
H["ROS Feedforward Loop<br/>Further DRP1 Activation"]
I["Neuronal Senescence<br/>AD CA1 Neuron Degeneration"]
A --> B
A --> C
C --> D
B --> E
D --> E
E --> F
E --> G
F --> H
G --> H
H --> B
F --> I
G --> I
style E fill:#7b1fa2,stroke:#ce93d8,color:#ce93d8
style I fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9aNo linked papers recorded for this hypothesis yet.
No curated PDB or AlphaFold mapping for DRP1 yet. Search RCSB →
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 DRP1,MFN1,MFN2,CDK5,PRKCD,PARK2,PTEN,PGC1A,OPA1.
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 DRP1 S616 phosphorylation is chronically blocked via neuronal-specific CDK5 knockdown in 3-month-old A53T α-synuclein mice (PRKCD upregulation model), THEN mitochondrial network fragmentation will | Aspect ratio ≥2.5 (vs. <1.5 in untreated A53T); MFN2 ≥80% of wild-type levels; mtROS ≤1.5-fold baseline | — no observation — | pending | 0.68 |
| IF AAV9-MFN2 overexpression combined with Mdivi-1 (DRP1 inhibitor) is administered to 6-month-old 5xFAD mice via bilateral hippocampal injection, THEN cortical and hippocampal SA-β-gal positivity will | ≥40% reduction in SA-β-gal+ neurons; ≥70% restoration of Complex I activity; ≥25% increase in synaptic density | — no observation — | pending | 0.72 |