Is it possible that cells identified as apoptotic by their viability plus Annexin V binding are actually undergoing a process of cell death or cycle arrest different to canonical apoptosis? For instance, piroptosis, oncosis, or other?
Cells undergoing pyroptosis open pores which are permissive to Annexin V and stain PS on the inner leaflet of the membrane. They can be differentiated from early apoptotic cells by also staining with 7-AAD and PI through the same pores.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3609431/pdf/nihms-445976.pdf
Annexin-V reacts with PS residues. Although maybe not regarded as regular cells, platelets display high labelling with Annexin-V upon activation.
Moreover, it has been shown that ABCB1 (an ABC superfamily transporter) also acts as a flippase of PS residues in plasma membrane. Hence, cells that overexpress ABCB1 protein exhibit high staining with Annexin-V as well. You can see this finding in the following paper: https://sciencescape.org/paper/12071854
Kind regards,
Raphael
PS may be exposed under a variety of circumstances: elevated cytosolic Ca2+ and decreased ATP levels may induce PS exposure. Some cells, such as macrophages, also stain relatively high with Annexin V under normal circumstances. In addition, certain conditions, such as Barth syndrome, may lead to PS exposure in otherwise healthy cells. Any form of cell death that leads to ATP depletion, Ca2+ elevation or plasma membrane permeabilization will therefore lead to Annexin V staining. This is also why you should always check for both permeability and Annexin V staining when determining cell death.
Bram and Raphael have explained it very well. In short, phosphatidylserine staining is not a definitive marker of apoptosis and other possible mechanisms could be playing a part, There is literature suggesting phosphatidylserine staining due to necrosis.
Thanks to all.
Saurabh, do you have any reference on PS staining in necrosis?
PS staining in necrosis is a "common" feature in experiments in vitro, but it should be evaluated whether it is a secondary effect of apoptosis. Following apoptosis in vitro, plasma membrane loses its integrity and so Annexin is able to stain its inner layer. If you have a reference in vivo of Annexin staining in necrosis, I also would like to read it too.
Kind regards to you all!!
Raphael
Hi,
I've been searching for some examples of non-apoptotic PS exposure recently. Here are some articles which I found on this topic:
PMIDs: 22084121, 16025105, 19846818.
In my experiments cells are expected (as shown by studies by other groups) to expose PS as a hallmark of apoptosis in response to a toxin, while they start growing again when I remove the toxin from the medium after 1-3 days. Doesn't look like apoptosis at all ;)
Lukasz
Thank you very much, Lukasz. Your resources are very useful. Things seem very interesting regarding SP exposure in cells not under canonical apoptosis.
We observed PS externalization as a result of the plasma membrane disturbance by pulsed electric fields. No apoptosis or necrosis were involved (BBA 2010, 1800:1210-1219). I think about PS externalization as a general indicator of membrane instability that, in turn, can be caused by multiple factors, and apoptosis is one of them.
Hi Enrique,
similarly as apoptotic cells, oncotic cells could exhibit external phosphatidylserine residues (PS) while maintaining membrane integrity
Article Multimodal Holographic Microscopy: Distinction between Apopt...
This is the example:
https://www.cell.com/cell-host-microbe/pdf/S1931-3128(17)30252-4.pdf
- Badges
- Science topic
- Similar topics
- Biological Science
- Molecular Cell Biology