The selective loss of cholinergic myenteric neurons in the aging colon, while nitrergic neurons remain numerically stable, suggests a subtype‑specific failure of proteostasis rather than a global collapse. We hypothesize that cholinergic neurons, facing declining ER‑associated degradation (ERAD) and heat‑shock response, divert soluble misfolded proteins into transient, membrane‑less aggregates that act as a protective sequestration hub. This aggregation is not a passive endpoint but an active, energy‑consuming attempt to keep toxic species soluble until autophagy can clear them. When autophagic flux falls below a critical threshold—due to age‑related lysosomal dysfunction—the aggregates mature into stable, lipofuscin‑laden deposits that impair neuronal function and trigger apoptosis. Nitrergic neurons avoid death because they maintain higher basal autophagy or rely on distinct stress‑granule dynamics that prevent aggregation progression.

Testable predictions

1. In aged rodents, cholinergic myenteric neurons will show increased co‑localization of ubiquitin, p62, and LC3‑II with soluble oligomeric species (e.g., SNAP‑25, synaptophysin) compared with nitrergic neurons, indicating active sequestration into autophagy‑competent assemblies.
2. Pharmacological enhancement of selective autophagy (e.g., spermidine treatment) administered before the onset of neuronal loss will increase autophagic flux specifically in cholinergic neurons, reduce the size and lipofuscin content of aggregates, and preserve ChAT‑positive neuron numbers without altering NADPHd‑positive nitrergic morphology.
3. Genetic knockdown of autophagy‑initiating genes (Atg5 or Becn1) selectively in cholinergic neurons of middle‑aged mice will accelerate aggregate maturation, exacerbate neuron loss (>50% reduction by 24 months), and worsen colonic transit times, whereas the same manipulation in nitrergic neurons will produce only mild hypertrophy.
4. Acute inhibition of ERAD (using the small‑molecule inhibitor KIF‑155) in young adult mice will precipitate early aggregate formation in cholinergic neurons and sensitize them to autophagy blockade, mimicking the aged phenotype.

Falsifiability If spermidine fails to improve autophagic markers or cholinergic neuron survival in aged animals, or if enhancing autophagy does not reduce aggregate load while rescuing function, the hypothesis that aggregation serves as a sequestration strategy dependent on autophagy clearance would be refuted. Conversely, demonstrating that aggregate dissolution without restoring autophagy leads to neuronal death would support the view that aggregates are protective rather than inherently toxic.

This mechanistic framework shifts the therapeutic focus from dissolving aggregates outright to bolstering the neuron’s capacity to safely sequester and later clear misfolded proteins, offering a precise, subtype‑targeted approach to age‑related colonic dysmotility.