FOXO4-DRI is a synthetic peptide built from the D-amino acid retro-inverso form of a sequence within the forkhead transcription factor FOXO4. It was designed by the de Keizer group and described in Cell in 2017 as a tool for disrupting the interaction between FOXO4 and p53 in senescent cells. At around 5.2 kDa it is one of the larger peptides in the research range, and it is used in cell culture models of senescence. NuVion supplies FOXO4-DRI as a laboratory chemical for in vitro research use only.
Key facts
| Type | Synthetic D-retro-inverso peptide |
| Amino acid count | Approximately 45 residues |
| Design | D-amino acids in reversed sequence order |
| Parent protein | FOXO4 forkhead transcription factor |
| Molecular target | FOXO4 to p53 protein interaction |
| Cell-penetrating element | N-terminal transduction sequence |
| Synonyms | FOXO4 DRI, FOXO4-D-retro-inverso peptide, Proxofim |
| Supplied form | Lyophilised powder in a sealed vial |
FOXO4-DRI
$199 AUD
View productResearch use only. Not for human or veterinary use.
Structure and chemistry
The retro-inverso design is the defining feature. A retro-inverso peptide is built from D-amino acids assembled in the reverse order of the parent L-sequence. The reversal of the backbone direction combined with the inversion of chirality at each alpha carbon means the side chains project in approximately the same spatial arrangement as in the parent, so the surface that a binding partner sees is largely preserved while the backbone amide bonds present a geometry that mammalian proteases do not recognise. The result is a peptide with a much longer half-life in serum-containing medium than the corresponding L-peptide.
FOXO4-DRI carries a cell-penetrating transduction sequence at its N-terminus fused to the interaction-blocking segment derived from the FOXO4 forkhead domain. The transduction element is what allows a peptide of this size to reach the nucleus of a cultured cell without transfection reagent, and it is the reason the compound can be applied directly to culture medium. The peptide carries a strong net positive charge because of the arginine-rich transduction element, which drives association with the negatively charged cell surface and with nucleic acid.
That basic character governs handling. The peptide is water-soluble but binds avidly to glass and to some plastics, so low-binding tubes and tips reduce losses at low working concentrations. It also associates with heparin, with serum polyanions and with DNA in lysates, which matters when designing pull-down or binding experiments. Purity is determined by RP-HPLC and identity by mass spectrometry, and because all residues are D-form the peptide is resistant to the standard enzymatic sequencing approaches, so identity confirmation relies on mass and on fragmentation pattern.
Mechanism of action
In cells that have entered senescence, FOXO4 is reported to associate with p53 and to hold it in nuclear foci, an arrangement that keeps p53 from relocating to the mitochondria where it would otherwise participate in apoptotic signalling. That sequestration is proposed to be part of why senescent cells persist instead of clearing. FOXO4-DRI is designed to occupy the FOXO4 interaction surface competitively, releasing p53 from the complex. The released p53 then becomes available for the mitochondrial route, and in senescent cell populations the readout is an increase in apoptotic markers.
The selectivity claim rests on the difference between senescent and proliferating cells in culture. Cells that have not entered senescence carry a different balance of FOXO4 and p53 and are reported to be largely unaffected at concentrations where senescent populations respond, which is what makes the compound useful as a senolytic tool for comparing the two states side by side. The cellular readouts are apoptosis by annexin V staining or caspase activity assay, senescence burden by senescence-associated beta-galactosidase staining, expression of p16 and p21 by qPCR or immunoblot, and the composition of the senescence-associated secretory phenotype measured in conditioned medium by multiplex immunoassay. Co-localisation of FOXO4 and p53 by immunofluorescence, before and after exposure, is the direct test of the proposed mechanism.
Research applications
- Senolytic screening in cultures where senescence has been induced by irradiation, oxidative challenge or replicative exhaustion, comparing senescent and proliferating populations.
- Apoptosis assays by annexin V flow cytometry or caspase 3 and 7 activity in paired senescent and non-senescent cultures.
- Senescence-associated beta-galactosidase staining to quantify senescent cell burden before and after exposure.
- Immunofluorescence co-localisation of FOXO4 and p53 to test complex disruption directly.
- Secretory phenotype profiling by multiplex immunoassay on conditioned medium, following interleukin and matrix metalloproteinase output.
- Comparison against small molecule senolytic tool compounds under matched conditions.
FOXO4-DRI sits in NuVion’s Cellular Ageing category alongside the other compounds used in senescence and telomere research.
Handling in the laboratory
FOXO4-DRI is supplied lyophilised and is reconstituted with bacteriostatic water added slowly to the vial and swirled until dissolved. The peptide is water-soluble, and because the transduction sequence is arginine-rich it should not be vortexed hard, since surface adsorption and foaming both cause loss. Low-binding tubes are used for stock and for working dilutions. The reconstitution calculator converts vial content and diluent volume into a stock concentration, and a vehicle control accounts for the benzyl alcohol carried over from the diluent.
Unopened vials are kept sealed, dry and refrigerated as stated on the product documentation. Reconstituted solution is refrigerated and used within the period given there, or aliquoted and frozen in single-use volumes. Aliquoting is particularly worthwhile for this compound because the working concentrations are low and each freeze-thaw plus each transfer between tubes costs material to adsorption. Unlike an L-peptide of similar size, degradation by proteases in serum-containing medium is not the limiting factor, so exposure windows in culture can be long.
Testing and supply from NuVion
NuVion’s FOXO4-DRI is manufactured at a GMP-audited facility and independently tested by Janoshik Analytical, with purity determined by RP-HPLC and identity confirmed by mass spectrometry. The Certificate of Analysis for a tested batch is published on the product page and in the COA library. The peptide is supplied lyophilised in sealed vials and dispatched from within Australia.
Related compounds
Other compounds used in cellular ageing research include Epithalon, studied in telomerase and telomere length assays, and NAD+, the cofactor for the sirtuin and PARP enzyme families.
Frequently asked questions
What is FOXO4-DRI used for in research?
It is used as a senolytic tool compound in cell culture, applied to populations in which senescence has been induced so that apoptotic response, senescence marker expression and secretory output can be compared against proliferating controls.
What does D-retro-inverso mean?
The peptide is assembled from D-amino acids in the reverse order of the parent L-sequence. Reversing the backbone and inverting the chirality together preserve the spatial arrangement of the side chains while giving a backbone that mammalian proteases do not cleave, so the peptide persists far longer in serum-containing medium.
Is FOXO4-DRI a therapeutic good in Australia?
No. NuVion’s FOXO4-DRI is a laboratory chemical for in vitro research. It is not included in the Australian Register of Therapeutic Goods, has not been assessed by the Therapeutic Goods Administration, and is not for human or veterinary use.
How should FOXO4-DRI be stored?
Lyophilised vials are kept sealed, dry and refrigerated per the product documentation. Reconstituted solution is refrigerated and used within the stated period, or aliquoted into single-use low-binding tubes and frozen to limit both freeze-thaw and adsorption losses.
Research use only. This product is a laboratory chemical supplied for in vitro research. It is not included in the Australian Register of Therapeutic Goods and has not been assessed by the Therapeutic Goods Administration for quality, safety or efficacy. It is not for human or veterinary use, and nothing on this page is a representation about therapeutic use.
