Circadian gating of ERK nuclear export via clock-controlled DUSP expression determines senescence susceptibility

Background

Sustained nuclear ERK1/2 activity drives p21/p53‑mediated G1/S arrest and cellular senescence[1], while cytoplasmic retention permits proliferation or senescence escape. ERK shuttling depends on importin7‑mediated nuclear import and phosphatase‑regulated export[2]. Genetic dampening of RAS/ERK signaling delays age‑related senescence[3], and MEK/ERK inhibition can trigger apoptosis when autophagy fails[4]. Yet no study links core circadian components to ERK localization.

Hypothesis

The circadian BMAL1/CLOCK complex directly drives rhythmic transcription of nuclear‑localized dual‑specificity phosphatases (DUSP6 and DUSP10), creating daily windows of efficient ERK dephosphorylation and export. Loss of circadian rhythm abolishes this phosphatase oscillation, leading to prolonged nuclear ERK residence and senescence induction.

Mechanistic rationale

1. Promoter binding – BMAL1/CLOCK heterodimers bind E‑box elements in the DUSP6 and DUSP10 promoters, a pattern seen in liver and muscle circadian transcriptomics (inferred from existing ChIP‑seq data).
2. Phosphatase rhythm – DUSP6/DUSP10 mRNA and protein peak during the early subjective night, coinciding with low nuclear ERK levels in synchronized fibroblasts.
3. Clock disruption – siRNA knockdown of Bmal1 or Per2 flattens DUSP expression, increases nuclear ERK‑p21 signaling, and accelerates senescence markers (SA‑β‑gal, p16).
4. Rescue – Forced expression of DUSP6 restores cytoplasmic ERK distribution and suppresses senescence even in arrhythmic cells.

Testable predictions

• In serum‑shocked human fibroblasts, the nuclear/cytoplasmic ERK ratio will show a ~24‑h oscillation inversely correlated with DUSP6/DUSP10 protein levels.
• Bmal1 knockout mice will exhibit elevated nuclear ERK in skeletal muscle and accelerated age‑dependent senescence compared with wild‑type littermates.
• Pharmacological enhancement of DUSP activity (e.g., with a selective DUSP6 agonist) will dampen ERK nuclear signaling and extend healthspan in circadian‑disrupted models.

Experimental approach

1. Synchronize NIH‑3T3 cells with serum shock, collect samples every 4 h for 48 h; perform subcellular fractionation, immunoblot for ERK‑p21, DUSP6/DUSP10, and quantify nuclear/cytoplasmic ratios.
2. Use CRISPR‑Cas9 to delete the E‑box in the Dusp6 promoter; assess impact on phosphatase rhythm and ERK localization.
3. Treat Bmal1‑deficient mice with a DUSP6‑activating compound; monitor senescence biomarkers (p16Ink4a, SASP) and frailty over 12 months.

Potential implications

If validated, the clock would act as a temporal gatekeeper of ERK‑driven senescence, positioning circadian reinforcement—not just clock repair—as a geroprotective strategy that targets a defined signaling node.

References

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6323238/ [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC8165001/ [3] https://journals.biologists.com/dmm/article/15/10/dmm049627/276620/Molecular-inhibition-of-RAS-signalling-to-target [4] https://www.aging-us.com/article/101325/text