FOXO4

FOXO4-DRI Peptide: p53 and Cellular Senescence Research Guide

FOXO4 is a human forkhead-box transcription factor involved in stress responses, insulin-related signaling, cell-cycle regulation, and DNA-damage biology. By contrast, FOXO4-DRI is a synthetic D-retro-inverso research peptide designed to model and disrupt a specific FOXO4–p53 protein-protein interaction. These names are often shortened in catalogs, but the full FOXO4 protein and a FOXO4-derived peptide are not interchangeable research materials.

The Hanpro Peptides product listed as FOXO4 is supplied as a lyophilized material for laboratory, analytical, in-vitro, and appropriately authorized preclinical research. The current catalog specification is 10mg × 10 vials. This amount describes packaging only and is not an experimental or clinical dose. Researchers must verify the exact sequence, stereochemistry, terminal chemistry, salt form, and peptide content on the lot-specific label and certificate before designing an experiment.

FOXO4 protein versus FOXO4-DRI peptide

Feature	Human FOXO4 protein	FOXO4-DRI research peptide
Molecular type	DNA-binding transcription factor	Synthetic cell-penetrating D-retro-inverso peptide
Reference length	505 amino acids for canonical human isoform	Published reference sequence contains 46 residues
Reference mass	Approximately 53.7 kDa	Approximately 5.36 kDa for the published free peptide
Primary research role	Transcriptional regulation and cellular stress signaling	Competitive perturbation of the FOXO4–p53 interaction
Sequence convention	Natural L-amino-acid protein	All-D retro-inverso design in the foundational study
Catalog specification	10mg × 10 vials; verify the supplied identity on lot documentation
Intended use	Laboratory research and analytical use only

The reviewed UniProt record P98177 describes canonical human FOXO4 as a 505-residue, approximately 53.7-kDa transcription factor. It contains a forkhead DNA-binding domain and multiple regulatory regions. FOXO4 activity and localization can be influenced by phosphorylation, acetylation, ubiquitination, oxidative stress, and interactions with proteins such as 14-3-3, SIRT1, CBP, and p53.

The FOXO4-DRI construct reported in the literature is different. PubChem lists the reference sequence as LTLRKEPASEIAQSILEAYSQNGWANRRSGGKRPPPRRRQRRKKRG and a molecular mass of approximately 5,358 g/mol. In the D-retro-inverso design, the amino-acid order and stereochemistry are arranged to mimic the side-chain topology of a parent L-peptide while potentially changing proteolytic stability. The cationic C-terminal segment functions as a cell-penetrating component. However, laboratories should not assume that every product marketed under a shortened “FOXO4” name has this exact composition.

FOXO4–p53 interaction in senescence research

Cellular senescence is a durable cell-cycle-arrest state that can arise after DNA damage, oncogene activation, telomere dysfunction, oxidative stress, or other insults. Senescent cells are heterogeneous. Depending on cell type and stimulus, they may express p16, p21, persistent DNA-damage markers, senescence-associated beta-galactosidase, altered chromatin, resistance to apoptosis, and a senescence-associated secretory phenotype (SASP). No single marker proves senescence in every system.

A 2017 Cell study identified FOXO4 as a factor supporting the viability of certain senescent cells. In the tested models, FOXO4 and p53 formed nuclear foci. The authors designed FOXO4-DRI to compete with this interaction. Treatment caused nuclear exclusion of active p53 and caspase-dependent apoptosis preferentially in senescent IMR90 fibroblasts under the reported conditions. The same paper evaluated doxorubicin-induced senescence, a progeroid mouse model, and naturally aged mice.

These findings established a research hypothesis, not a universal rule. Cell type, senescence inducer, time after induction, p53 status, FOXO4 abundance, peptide uptake, and apoptotic competence can all affect the result. A dividing-cell control is necessary, but it is not sufficient by itself. Researchers should also compare multiple non-senescent and senescent conditions and determine whether loss of viability is p53- and caspase-dependent.

Structural insight from recent research

A 2025 study used solution NMR and complementary methods to characterize binding among the FOXO4 forkhead domain, FOXO4-DRI, and the p53 transactivation region. The work identified the disordered p53 TAD2 region as an important target and showed that both the FOXO4-derived region and the cationic cell-permeability segment of FOXO4-DRI contribute to the interaction. It also reported stronger binding after p53 phosphorylation in the tested system.

This structural evidence is useful for mechanism and analog-design studies. For example, researchers can compare FOXO4-DRI with the corresponding L-amino-acid peptide, a scrambled control, a cell-penetrating segment alone, or shorter analogs. Binding assays should be paired with cell-based work because affinity, intracellular delivery, localization, stability, and functional response are distinct properties.

Research applications

1. Senescent-cell selectivity

Researchers can compare viability and apoptosis in matched proliferating and senescent cultures. Senescence may be induced by replicative exhaustion, irradiation, oxidative stress, oncogene activation, chemotherapy, or extended culture. Each method creates a different phenotype, so the induction protocol, recovery interval, passage number, and baseline markers must be reported.

Useful endpoints include live-cell imaging, cell counts, membrane-integrity assays, annexin-V labeling, caspase-3/7 activation, mitochondrial-potential measurements, and clonogenic recovery. A metabolic assay alone can confuse growth arrest with cell death. Furthermore, apparent selectivity should be expressed across a complete concentration-response and time course rather than at one chosen condition.

2. FOXO4–p53 protein-protein interaction

Biochemical and cellular studies can investigate binding, competition, nuclear foci, and protein localization. Potential methods include NMR, surface-plasmon resonance, isothermal titration calorimetry, fluorescence polarization, pull-down, co-immunoprecipitation, proximity ligation, and microscopy. Confirm that the assay format preserves the relevant domains and post-translational state.

FOXO4 and p53 are multifunctional proteins. Therefore, a phenotype following peptide exposure does not by itself prove disruption of their interaction. Genetic FOXO4 or TP53 perturbation, rescue experiments, peptide controls, and direct target-engagement measurements strengthen attribution.

3. p53 localization and apoptotic signaling

The foundational FOXO4-DRI model connects disruption of nuclear FOXO4–p53 foci with p53 redistribution and cell-intrinsic apoptosis. Researchers may quantify nuclear and cytosolic p53, p53 phosphorylation, p21, BAX-family signaling, mitochondrial events, and caspase activation. Cell fractionation should include compartment markers, while microscopy should use blinded analysis and predefined segmentation rules.

4. SASP and tissue-model research

Published studies have examined FOXO4-DRI in expanded human chondrocytes, senescent Leydig-cell models, fibrosis models, endothelial-cell senescence, and aged animals. Results vary by system. For example, removal of senescent expanded chondrocytes reduced some senescence-associated secretory markers but did not restore chondrogenic potential in the tested pellet model. Such findings illustrate why clearance of a marker-positive population should not automatically be equated with functional rejuvenation.

For SASP research, measure a panel of secreted factors rather than one cytokine and normalize to viable cell number. In tissue or organoid work, pair molecular markers with functional endpoints, histology, and cell-type-resolved analysis. Changes after senescent-cell depletion can arise from altered cell composition as well as direct pathway modulation.

Experimental design and controls

• Verify material identity: confirm whether the supplied item is FOXO4-DRI, an L-amino-acid comparator, another FOXO4-derived sequence, or full-length protein.
• Characterize senescence: use multiple markers appropriate to the cell type and inducer, including arrest, DNA-damage, lysosomal, and secretory endpoints.
• Include matched populations: compare proliferating, quiescent, stressed non-senescent, and senescent cells where feasible.
• Measure target engagement: pair viability with FOXO4–p53 interaction or localization readouts.
• Test mechanism: use TP53 or FOXO4 perturbation, caspase inhibition, rescue designs, and sequence controls when relevant.
• Control delivery: quantify uptake and intracellular localization; highly cationic peptides can bind membranes and surfaces nonspecifically.
• Assess off-target toxicity: include diverse non-senescent cell types and membrane-integrity, apoptosis, and longer-term recovery assays.
• Report rigorously: document lot, stereochemistry, salt form, solvent, matrix, concentration, timing, passage, replicates, exclusions, and statistical plan.

Handling and analytical quality

Review the product label, safety information, and lot-specific certificate before opening. Establish a qualified laboratory procedure for solvent, pH, concentration, mixing, container, temperature, hold time, and freeze-thaw exposure. This page intentionally provides no injection route, human dose, or self-administration instructions.

Cell-penetrating and highly cationic peptides can adsorb to plastic, bind serum proteins, aggregate, or show matrix-dependent recovery. Low-binding consumables and recovery controls may be useful, but laboratories should validate them under their exact conditions. Nominal concentration and freely available concentration may differ.

Reversed-phase HPLC or UPLC can support purity and degradation profiling, while LC-MS or high-resolution MS can confirm mass and identity. Confirming D-amino-acid stereochemistry or retro-inverso design may require additional orthogonal analysis beyond routine mass spectrometry. Chemical purity does not establish p53 binding, cellular entry, or senescent-cell selectivity; these require fit-for-purpose functional assays.

Frequently asked questions

Is FOXO4-DRI the same as the FOXO4 protein?

No. Human FOXO4 is a 505-residue transcription factor. FOXO4-DRI is a much shorter synthetic D-retro-inverso peptide derived from a FOXO4 interaction region and joined to a cationic cell-penetrating sequence. Confirm the exact identity of the supplied material on lot documentation.

What does D-retro-inverso mean?

It refers to a peptide design that reverses sequence orientation and uses D-amino acids to approximate the side-chain topology of a parent L-peptide. This can change protease susceptibility and binding behavior. It does not guarantee identical activity, stability, or selectivity in every assay.

Is FOXO4-DRI proven to reverse aging?

No. Published evidence includes mechanistic cell studies and animal models. These experiments do not establish safety or efficacy for human anti-aging use. This catalog material is not an approved medicine and must not be administered to humans or animals.

What research concentration should be used?

There is no universal concentration. Select a range from peer-reviewed work using a closely matched cell type, senescence inducer, matrix, peptide identity, and endpoint, then validate it with uptake, concentration-response, time-course, target-engagement, and toxicity controls. The 10mg vial size is not a dosing recommendation.

Can senescence be identified with one marker?

No. Senescence is heterogeneous, and common markers are not individually specific. Use a panel that combines stable growth arrest with appropriate DNA-damage, lysosomal, chromatin, morphology, and secretory features.

How should prepared peptide be stored?

Follow the current label and lot-specific certificate. Solution stability depends on sequence, stereochemistry, salt form, buffer, pH, concentration, container, temperature, protein content, and freeze-thaw history. Establish acceptable conditions with a stability-indicating method.

Does a mass match confirm every aspect of peptide identity?

No. Mass confirmation alone does not establish stereochemistry, sequence orientation, chromatographic purity or functional activity. Review lot-specific identity evidence and select orthogonal analytical and functional controls appropriate to the research question.

Related cellular-stress research materials

• SS-31 – aromatic-cationic peptide for mitochondrial membrane and cardiolipin research.
• MOTS-c – mitochondrial-derived peptide for metabolic and stress-signaling studies.
• Humanin – mitochondrial-derived peptide studied in cellular-stress and survival models.

Additional catalog navigation is available for AICAR, 5-Amino-1MQ, reduced glutathione, NAD+, and Pinealon. These are separate research materials, not substitutes for FOXO4-related peptides. Links do not recommend administration or combinations; assess each material’s identity and evidence independently.

Selected scientific references

• UniProt P98177: reviewed human FOXO4 protein entry.
• PubChem: FOXO4-DRI reference sequence and molecular properties.
• Foundational 2017 study of FOXO4–p53 disruption in senescent-cell and mouse models.
• 2025 NMR characterization of p53 interactions with FOXO4 and FOXO4-DRI.
• FOXO4-DRI study in expanded human chondrocytes.
• FOXO4-DRI research in senescent Leydig-cell and aged-mouse models.
• Molecular modeling and peptide design targeting FOXO4–p53 interactions.

Research-use disclaimer

FOXO4-related peptide material from Hanpro Peptides is supplied strictly for laboratory research and analytical use. It is not a medicine, dietary supplement, cosmetic, or veterinary product. It must not be used for human or animal consumption, administration, diagnosis, treatment, or prevention of disease. Purchasers are responsible for confirming molecular identity, lawful procurement, institutional approval, risk assessment, safe handling, storage, experimental suitability, and disposal.