I work with Jurkat cells. A relatively high concentration (up to 500 uM) of small peptide (4 aa) is added to growth medium and pinocytosed by cells. The peptide shouldn't have any effect, but it elevates viability of cells with activated Fas receptor. Non-significantly, but anyway, I try to find an explanation. May it cause a metabolic impact that counteract apoptosis? I've found such info about glucose and lipids, but not about peptides...
Yes. Any molecule bathing a cell can be internalized by fluid pinocytosis or adsorptive endocytosis if the molecule binds to the membrane surface. However, whether the peptide, in your case, survives the event intact and is somehow released from the endosome into the cytosol is another matter. Another factor is the length of time the treatment is allowed to occur. While passive diffusion is likely very slow, as peptidic HIV protease inhibs were, a 3-day assay may be sufficient to allow for target engagement.
I examined the permeability of that peptide conjugated to FITC. It enters cells very quicly (30 min is sufficient, probably faster). Moreover, in addition to cytoplasm, it localizes in some cell compartments (working on identification). So it is clearly endocytosis.
The problem is that this process shouldn't logically have any positive influence on cells (the peptide is actually negative control) but it has, statistically insignificant though.
But I think I've just found some sort of explanation. The peptide may be degraded and some aminoacid may help cells. For example, de-novo serine syntesis is upregulated during hypoxia (Jiangbin Ye et al,Cancer Discov. 2014). My control peptide contains serine that potentially can be used by cells. Conditions of apoptosis is also somehow similar to hypoxia... and so on.
Yes, depending of culture media composition and time of cultivation mentioned above peptide could be additional source of substrates for tricarboxylic acid (TCA) cycle and account to NAD+/NADH balance related mechanisms of cell metabolism and fate regulation. As alternative hypothesis peptide could be source of pool of small molecules with antioxidant properties and thus modulate apoptotic processes.
Daniil R. Petrenyov, thank you for your answer.
P.s. This peptide is not anti-oxydative, but those with cysteines are truly anti-apoptotic.
- Badges
- Science topic
- Similar topics
- Biological Science
- Cell Biology