Proaerolysin

Recently we have been talking about paroxysmal nocturnal hemoglobinuria and its detection in general (here), now we will focus on detection of the GPI anchor. Glycosyl phosphatidyl inositol (GPI) is a component of the plasma membrane and represents an important mechanism how to keep particular proteins attached to cell surface. As the GPI-anchored proteins do not have any transmembrane domain, the dynamics of their interactions during formation of signaling microdomains within the plasma membrane is different compared to the transmembrane proteins, and they can also be easily cleaved from the cell surface, when needed. However, GPI has been abused by a gram negative bacterium Aeromonas hydrophila to attack eucaryotic cells, as GPI is a target of its toxin called aerolysin. While natural aerolysin forms pores in the plasma membrane upon binding to GPI, its genetically mutated variant only binds to the GPI anchor without damaging the membrane. Hence fluorescently labeled inactivated proaerolysin (FLAER) is optimal marker for detection of presence of GPI anchors on the cell surface. There is a great advantage in this case, that more cell populations can be detected by this universal approach, whereas when only monoclonal antibodies are used, there is no particular GPI-anchored protein available, that would be expressed on all cell populations that are needed to be examined during PNH diagnostics, and on the other hand, there are some proteins that have both GPI-anchored and transmembrane isoform, and these can not be used as good PNH markers, when only detection by antibodies is involved. Fluorescently labeled proaerolysin thus represents a powerful tool in PNH diagnostics.

Fig. 1: Schematic drawing of a fluorescently labeled proaerolysin attachment to a GPI anchor. This interaction does not depend on the GPI-anchored protein itself.
 
 
SingleFlowEx Proaerolysin Alexa Fluor® 488:     ED7751
 
DryFlowEx PNH High-Sensitivity Assay Kit:         ED7750