Nucleolar ribosome biogenesis hub proteins drive sex‑specific aging via cytokine‑mediated proteostasis collapse
Hypothesis
The 265 super‑central proteins identified in the human aging interactome act as a nucleolar‑centric hub that couples ribosome biogenesis to ubiquitin‑mediated quality control. When these hub proteins become dysregulated with age, they trigger nucleolar stress, causing the release of nuclear alarmins (e.g., IL‑1α, HMGB1) that act as cytokines to coordinate a body‑wide proteostatic decline. This mechanism explains why nucleolar ribosome biogenesis disorganization precedes other hallmarks, why nearly half of age‑changes are sex‑specific (female‑biased immune activation), and why targeting canonical longevity proteins like mTOR yields inconsistent lifespan effects.
Key predictions
- Selective knockdown or CRISPR‑mediated reduction of individual hub proteins in mouse liver and brain will increase nucleolar stress markers (e.g., nucleolar enlargement, reduced pre‑rRNA) and elevate circulating alarmin cytokines within 2 weeks.
- The cytokine surge will precede detectable declines in proteostasis reporters (e.g., ↑ ubiquitinated proteins, ↓ HSP70) in distal tissues such as spleen and skin.
- Female mice will show a larger cytokine response and faster proteostasis collapse than males, mirroring the observed broader immune activation.
- Rescue of nucleolar integrity by overexpressing a nucleolar chaperone (e.g., nucleophosmin) or neutralizing the released cytokine (anti‑IL‑1α antibody) will restore proteostasis and extend median lifespan, whereas similar interventions in males will produce a smaller effect.
- In human induced pluripotent stem cell‑derived organoids, sex‑specific differences in hub‑protein expression will correlate with basal nucleolar stress and cytokine secretion.
Falsifiability If hub‑protein perturbation fails to raise nucleolar stress or cytokine levels, or if cytokine blockade does not delay proteostasis decline and lifespan extension, the hypothesis is refuted. Likewise, if sex differences disappear after controlling for hormonal milieu, the sex‑specific claim is invalidated.
Experimental outline
- Identify top 10 hub proteins from the 265 list (highest betweenness centrality, ribosomal/ubiquitination annotation).
- Generate inducible shRNA or CRISPRi mouse lines for each target, with sex‑balanced cohorts.
- Measure nucleolar size (fibrillarin staining), pre‑rRNA levels (qRT‑PCR), circulating IL‑1α/HMGB1 (ELISA) at 1, 4, 8 weeks post‑induction.
- Assess proteostasis via GFP‑clon sensor in peripheral tissues and ubiquitin‑positive inclusions.
- Monitor frailty index and survival.
- Parallel experiments with anti‑IL‑1α treatment or nucleophosmin overexpression.
- Validate in male/female iPSC‑derived liver and brain organoids.
Broader impact Confirming this hub‑centric, cytokine‑mediated mechanism would reposition nucleolar stress as a primary driver of aging, provide sex‑specific biomarkers (nucleolar size, IL‑1α), and suggest combinatorial therapies targeting both ribosome biogenesis regulators and cytokine signaling to delay multisystem decline.
References