Autophagy and proteostasis — two cleanup systems
Autophagy and the proteasome both help maintain a cell, but their abundance does not establish which system the cell depends on.
Before you start: Flux and dependence explains why a snapshot differs from a moving process.
Two routes for cellular cleanup
The proteasome breaks down many individual proteins marked with ubiquitin. Autophagy encloses selected cargo in a membrane compartment, which joins a lysosome for breakdown and recycling. The systems overlap, compensate and respond to stress. Losing one route does not invariably make a cell sensitive to a drug blocking the other.
Why the direction matters
ATG13 and RB1CC1/FIP200 help initiate an autophagosome through the ULK machinery. ATG4B processes LC3-family proteins. A predicted damaging change in one gene does not prove that pathway flow has collapsed: the change must be authentic, expressed and consequential in the relevant cells.
High LC3-II or many autophagosomes can reflect increased formation or impaired clearance. The same crowded-road photograph can show productive deliveries or a blocked warehouse. The analogy ends at measurement: a dynamic assay, such as comparison with and without lysosomal blockade, is needed to distinguish those states.
What can go wrong
Bulk RNA reflects captured transcripts from a tissue mixture. A high pathway score can reflect preparation, cell composition or a reference mismatch. A rank does not measure flux. A drug response can also have several causes; it does not independently validate the proposed genotype-to-dependence story.
Bortezomib blocks proteasome function. Chloroquine-related compounds disrupt lysosomal processes. Which perturbation is informative depends on the observed state and exposure. Preclinical evidence for compensation or stress responses does not establish a clinical combination or postoperative benefit.
A worked experiment
Compare a specified perturbation with appropriate controls in a tumor-relevant model. Measure flux, viability and the relevant molecular consequence. Where feasible, restoring the affected function can test whether the proposed mechanism accounts for the result. A response that persists after rescue weakens that causal explanation.
Try it
A sample has high LC3-II. Does adding a late autophagy blocker test a proven dependence?
Answer: No. First distinguish increased formation from failed clearance, then test whether the process supports survival under the specified conditions.
Explain it back
“RNA abundance describes captured messages; flux describes movement through a pathway; dependence requires a perturbation that changes survival.”
Applied to Diana
The source-specific history and withdrawal of the earlier variant/rank premises are retained in the report overview and the qualified research review. They do not establish a current autophagy treatment priority.
Takeaway
Measure pathway flow and causal dependence before interpreting a gene list or RNA rank as a drug strategy.
Next: Lipid metabolism and mTOR.
Sources and scope
Updated October 8, 2026; general pathway teaching; expert and learner review pending.