Scientists have designed a small cell-penetrating peptide that disrupts the binding between the deubiquitinating enzyme USP25 and the longevity regulator SIRT1, and in mouse and cell experiments the intervention increased SIRT1 deacetylase activity and reduced hallmark signs of cellular senescence. The work, published in Aging Cell, positions the USP25–SIRT1 axis as a candidate target for future antiaging drug development, although all findings so far come from laboratory models rather than human trials.
The research team, led from Tongji University, began by noting that USP25 protein levels rise in the livers of 20-month-old C57BL/6 mice compared with 5-month-old animals, while USP25 mRNA levels stay unchanged, suggesting the increase is regulated after transcription. The same pattern appeared in human MCF-10A breast epithelial cells pushed into senescence by the chemotherapy drug doxorubicin: USP25 protein rose sharply while its mRNA did not. Because USP25 is a deubiquitinating enzyme that removes ubiquitin chains from substrate proteins, the investigators suspected it might modify the stability or function of proteins involved in aging.
Genetic evidence supported that suspicion. Mice lacking USP25 lived longer than their wild-type littermates in a 20-month survival study, with a log-rank test giving p = 0.0313, and they performed better on a rotating-rod coordination test at 5 and 20 months of age. In the knockout animals, P21, a widely used senescence marker, was lower in lung, liver, brain, heart and kidney tissue, and staining for alkaline phosphatase and tartrate-resistant acid phosphatase revealed more bone-forming osteoblasts and fewer bone-resorbing osteoclasts, indicating alleviation of age-related bone loss. The knockout mice also weighed less and had a lower liver-to-body-weight ratio than controls at 10 months.
To test whether USP25 drives aging rather than merely accompanying it, the researchers used a D-galactose model, an established accelerated-aging protocol in which mice receive daily injections of the sugar for eight weeks. Both untreated and D-galactose-treated Usp25-deficient mice stayed on the rotarod longer than wild-type controls, and their livers showed reduced P21 protein and weaker P21 staining. RNA sequencing of liver tissue from 10-month-old knockout mice further revealed suppressed inflammatory and apoptotic gene sets by gene set enrichment analysis, consistent with a broad dampening of senescence-associated biology.
The mechanistic core of the study emerged from mass spectrometry, which identified SIRT1 as a previously unknown USP25-interacting protein. Coimmunoprecipitation in HEK-293T cells confirmed the physical association. Crucially, USP25 did not change SIRT1 protein abundance; instead, it removed K63-linked polyubiquitin chains from SIRT1, a modification type that typically regulates protein activity rather than degradation. When USP25 was knocked down, SIRT1 ubiquitination rose, and the increase was specific to K63 chains rather than the K48 chains that mark proteins for proteasomal destruction. Mass spectrometry pinpointed lysines 506 and 513 on SIRT1 as the principal deubiquitination sites, residues conserved across humans, mice, rats, goats, cattle, horses and rabbits.
Functional assays showed why this matters. SIRT1 is an NAD+-dependent deacetylase that counters senescence by deacetylating targets such as P53 and PGC1α. Removing USP25 increased SIRT1 deacetylase activity in cells and in mouse tissues, lowered P53 acetylation at lysine 382, reduced P21 expression and cut the fraction of SA-β-gal-positive senescent cells. The effect vanished when SIRT1 itself was depleted, demonstrating that USP25 acts on senescence through SIRT1. Ubiquitination at K506 and K513 proved critical: a SIRT1 mutant carrying arginine substitutions at those two lysines was immune to USP25 loss, retaining normal deacetylase activity and senescence suppression.
The study also clarified how ubiquitination status influences SIRT1 function. USP25 knockdown weakened the binding between SIRT1 and DBC1, a nuclear protein known to inhibit SIRT1 deacetylase activity upon direct binding. In cells expressing wild-type SIRT1, USP25 loss reduced the SIRT1–DBC1 interaction, but the K506/K513 mutant did not show this change, indicating that the two lysine residues govern how ubiquitination controls DBC1 access. In mice treated with the SIRT1 inhibitor EX527 during D-galactose exposure, the senescence-lowering effect of USP25 deletion was reversed, P53 acetylation returned, and mRNA levels of the senescence-associated secretory phenotype factors MMP9, CXCL1 and Serpine1 rose again, reinforcing the SIRT1–P53 dependence of the pathway in vivo.
Building on this mechanism, the team designed four cell-penetrating peptides based on the coiled-coil-like domain of SIRT1 that the mapping experiments identified as the USP25 binding region. Surface plasmon resonance showed all four peptides bound USP25 with high affinity, but only pSirt1-4, with the sequence HLYVSPWWPNRVAKEQISRRLD, actually disrupted the endogenous USP25–SIRT1 interaction in cells. Treatment with pSirt1-4 increased SIRT1 ubiquitination in cells expressing wild-type SIRT1 but not the 2KR mutant, raised SIRT1 deacetylase activity, reduced P53 acetylation and P21 levels, and lowered SA-β-gal staining in doxorubicin-induced senescent MCF-10A cells.
In vivo, wild-type mice receiving pSirt1-4 alongside D-galactose showed fewer P21-positive cells and reduced SA-β-gal activity in tissue staining compared with mice given a scrambled control peptide. Serum measurements of AST, urea and creatinine revealed no significant changes, suggesting the peptide did not cause overt liver or kidney toxicity under the tested conditions. The authors emphasize that these results demonstrate potential rather than proven clinical benefit, and that the peptide’s long-term safety, optimal dosing and efficacy in natural aging remain to be established.
Several limitations temper the conclusions. The authors note that pharmacological inhibition of SIRT1 with EX527 cannot fully replicate genetic deletion, and that generating Usp25/Sirt1 double-knockout mice is technically difficult because germline Sirt1 loss causes developmental defects and perinatal lethality. They also acknowledge that USP25’s established roles in inflammation and immunity mean indirect immune effects could contribute to the systemic improvements observed, and that the evidence from knockout models and limited age points is not yet sufficient to prove USP25’s importance in natural aging. Future work with conditional knockouts and multiple time points will be needed to determine whether the USP25–SIRT1 axis can be translated into a genuine antiaging therapy for humans.
Subject of Research: A cell-penetrating peptide that blocks the USP25–SIRT1 interaction to increase SIRT1 activity and suppress cellular senescence in mice.
Article Title: A Novel Peptide Targeting the USP25–SIRT1 Interaction Activates SIRT1 to Suppress Cell Senescence
Article References: Zhou, Y., Wang, X., Zhang, J., Qiang, H., Zhao, X., Luo, J., Ji, Y., Yao, J., Zhai, L., Zhang, T., Li, K., Chen, Y., Yuan, J., Li, L., & Li, Y. (2026). A Novel Peptide Targeting the USP25 – SIRT1 Interaction Activates SIRT1 to Suppress Cell Senescence. Aging Cell, 25(11), Article e70786. https://doi.org/10.1111/acel.70786
Image Credits: AI Generated
DOI: 10.1111/acel.70786
Keywords: USP25, SIRT1, deubiquitination, cellular senescence, cell-penetrating peptide, D-galactose aging model, P53 acetylation, DBC1, aging, Aging Cell, K63-linked ubiquitin, preclinical
News Source: Beatrice Stafford. (November 7, 2026). Peptide Blocks USP25–SIRT1 Binding to Ease Cell Aging in Mice. Scienmag.
