FOXO4-DRI is a synthetic peptide that is actively researched regarding its potential to induce programmed cell death in aged cells, and thus reduce the burden that aged cells pose on different tissues. Apparently, the peptide achieves that by mimicking a part of the so-called FOXO4, which is a transcription factor switching genes on and off in the DNA of cells. Notably, FOXO4 appears to be at higher levels in aged cells and may deactivate another protein called p53 that works to trigger programmed cell death.
According to researchers such as Baar et al., FOXO4-DRI peptide appears to be designed to imitate a small binding region of FOXO4 that otherwise may interact with p53 and mitigate it from triggering apoptosis.(1) The “DRI” part stands for D-retro-inverso, suggesting it was synthesized using D-amino acids and arranged in a reversed order compared with the original L-peptide fragment from FOXO4. This apparently works to make the binding region similar to the original, while making the whole molecule much more stable. Specifically, FOXO4-DRI peptide has been researched as a decoy that may compete with FOXO4 for p53 binding, so it may disrupt the FOXO4–p53 interaction in laboratory systems. This may leave p53 unbound, so that it may target senescent cells for apoptosis.
Researchers such as Huang et al. have investigated the apparent selectivity of FOXO4-DRI peptide in regard to specifically targeting aged cells for apoptosis.(2) To investigate this, the researchers studied in depth the apparent disruption of FOXO4–p53 binding and suggested that by disrupting it, the FOXO4-DRI peptide may shift p53 trafficking toward the mitochondria. Mitochondrial p53 is apparently linked to intrinsic apoptosis signaling, so this relocalization is posited to increase susceptibility to apoptosis specifically in senescent cells. Consequently, the authors suggest that the peptide may engage a caspase-3/7-dependent route downstream of mitochondrial stress.
The selectivity of the peptide is further discussed by the researchers, who suggest that senescent cells may depend more strongly on FOXO4-mediated control of p53 localization and activity, so disrupting that node might preferentially remove cells that are already operating close to an apoptotic threshold. In contrast, cells with lower senescence burden may have less FOXO4–p53 dependence, or may buffer p53 relocalization through other regulators, which might explain the limited apoptosis in younger cultures compared to aged cell cultures.
After evaluating the peptide on aged cell cultures, the researchers apparently observed reduced senescence-associated staining and lower protein levels of p16, p21, and p53 in the remaining cell population, consistent with the removal of cells that highly expressed these markers. For example, the researchers conducted experiments with cartilage cells and noted that “FOXO4-DRI [may] remove the senescent cells in PDL9 chondrocytes”.
FOXO4-DRI is a synthetic peptide that is actively researched regarding its potential to induce programmed cell death in aged cells, and thus reduce the burden that aged cells pose on different tissues. Apparently, the peptide achieves that by mimicking a part of the so-called FOXO4, which is a transcription factor switching genes on and off in […]