Hypothesis

In aging neurons, chronic oxidative stress triggers a selective autophagy program that targets base excision repair (BER) enzymes—specifically OGG1 and APE1—for lysosomal degradation. This is not a generic clearance mechanism but a rationing decision: the cell sacrifices DNA repair capacity to mobilize amino acids and sustain essential bioenergetic processes under prolonged siege. Consequently, autophagy activation exacerbates 8‑oxoguanine accumulation and accelerates neurodegeneration.

Mechanistic Rationale

• Oxidative modifications (e.g., carbonylation, sulfonylation) on OGG1 and APE1 create epitopes recognized by the autophagy adaptor p62/SQSTM1.
• p62 binds both ubiquitinated BER proteins and LC3 on nascent autophagosomes, directing them into the lysosome.
• Lysosomal degradation releases glutamate, aspartate, and other metabolites that feed the TCA cycle, supporting ATP production when glycolytic flux is limited by mitochondrial damage.
• This trade‑off mirrors the "siege" analogy: the neuron cannibalizes its genome‑maintenance machinery to keep the lights on.

Testable Predictions

1. Inhibition of lysosomal autophagy preserves BER activity

   • Neurons treated with chloroquine, bafilomycin A1, or with ATG5/ATG7 knock‑down will show higher OGG1/APE1 protein levels and lower 8‑oxoguanine immunostaining after paraquat or H₂O₂ exposure compared with controls.

2. Enhanced autophagy accelerates BER loss

   • Rapamycin or Torin1 treatment will increase p62‑dependent co‑immunoprecipitation of OGG1/APE1 with LC3, reduce BER incision activity in nuclear extracts, and elevate mitochondrial DNA release into the cytosol.

3. Metabolite supplementation rescues the rationing effect

   • Providing cell‑permeable glutamate or aspartate will attenuate the autophagic decline of OGG1/APE1 under oxidative stress, indicating that nutrient salvage drives the selective degradation.

4. p62 is required for the effect

   • CRISPR‑mediated p62 knockout in primary cortical neurons will block autophagic loss of OGG1/APE1 despite intact LC3 lipidation, uncoupling general autophagy flux from BER enzyme turnover.

Experimental Approach (Outline)

• Model: Primary rat hippocampal neurons or human iPSC‑derived neurons aged in vitro via chronic low‑dose rotenone.
• Interventions: (a) Autophagy inhibitors (chloroquine 10 µM), (b) Autophagy inducers (rapamycin 100 nM), (c) p62 sgRNA, (d) Metabolite rescue (5 mM glutamate).
• Readouts: Western blot for OGG1, APE1, p62, LC3‑II; immunofluorescence for 8‑oxoguanine and γH2AX; comet assay for strand breaks; Seahorse ATP production; cytosolic mtDNA quantified by qPCR; cytokine release (IFN‑β) as readout of c‑GAS‑STING activation.

Falsification Criteria

If lysosomal blockade fails to increase OGG1/APE1 levels or reduce 8‑oxoguanine, or if p62 loss does not prevent BER enzyme degradation, the hypothesis that autophagy selectively rations BER enzymes under oxidative siege would be refuted. Conversely, confirmation of the predictions would support a model where autophagy’s role in aging neurons shifts from housekeeping to a damaging triage that fuels genomic instability.