Hypothesis

Sex-specific TORC1 activity drives progressive rewiring of hub proteins in the aging interactome, leading to organ‑specific functional decline. We predict that in male mice, heightened TORC1 signaling accelerates loss of connectivity among mitochondrial‑associated hubs in skeletal muscle, whereas in female mice, attenuated TORC1 preserves these hubs longer but promotes rewiring of nuclear‑envelope hubs linked to transcriptional dysregulation. This divergence explains ~40% of sex‑dependent age‑related cellular shifts observed across organs.

Testable Predictions

1. Direct interactome mapping: Using hybrid PL/XL‑MS on tibialis anterior muscle from young (3 mo), middle (12 mo), and old (24 mo) male and female C57BL/6J mice, we will quantify changes in degree centrality of known TORC1‑regulated hubs (e.g., RPTOR, AKT1S1, MAPK1). We expect a significant decline in hub degree for males between 12‑24 mo that is absent or delayed in females (p<0.01, two‑way ANOVA with sex×age interaction).

2. Pharmacological rescue: Chronic low‑dose rapamycin (14 ppm) administered from 12 mo onward will normalize hub degree trajectories in males to resemble female controls, without altering female hub dynamics. Failure of rapamycin to affect male hub rewiring would falsify the causal role of TORC1.

3. Organ‑specific extension: Parallel hybrid PL/XL‑MS in liver and brain will reveal that females exhibit earlier loss of nuclear‑envelope hub connectivity (e.g., LBR, LMNA) correlating with increased transcriptional noise, whereas males show preservation of these hubs but earlier mitochondrial hub loss.

Mechanistic Insight

We propose that sex‑biased expression of the TORC1 regulator DDIT4 (higher in females) creates a buffering capacity that delays mitochondrial hub disassembly but shifts stress toward nuclear‑envelope maintenance pathways. Conversely, lower DDIT4 in males permits unchecked TORC1‑driven phosphorylation of hub proteins, promoting their ubiquitination and extraction from complexes. This model integrates the conserved TOR‑enriched longevity network [1] with the observed sex‑dependent cellular shifts [4] and addresses the causality gap by proposing a reversible, signaling‑driven mechanism [7].

Falsifiability

If hybrid PL/XL‑MS shows no sex‑by‑age interaction in hub degree changes, or if rapamycin equally affects both sexes or has no effect, the hypothesis is refuted. Likewise, if DDIT4 knockdown in females does not accelerate male‑like mitochondrial hub loss, the proposed regulatory node is invalid.

References

[1] https://journals.plos.org/plosgenetics/article?id=10.1371%2Fjournal.pgen.1000414 [2] https://academic.oup.com/nargab/article/6/4/lqae153/7912061 [3] https://red.library.usd.edu/honors-thesis/270/ [4] https://www.rockefeller.edu/news/39031-scientists-map-how-aging-reshapes-cells-across-the-entire-mammalian-body/ [5] https://pmc.ncbi.nlm.nih.gov/articles/PMC8650568/ [6] https://pubs.acs.org/doi/10.1021/acs.jproteome.9b00609 [7] https://pmc.ncbi.nlm.nih.gov/articles/PMC11630784/