Why erythrocytes of different species present different susceptibility towards HlyA of E. coli?

ROMINA VAZQUEZ; VANESA HERLAX; SABINA MATÉ; CLAUDE WOLF; LAURA BAKÁS

Bilbao

Congreso; 51st International Conference on the Bioscience of Lipids; 2010

ICBL

Alpha-hemolysin (HlyA) is an exotoxin secreted by some pathogenic E.coli strains that causes lysis of various mammalian cells, including erythrocytes of different animal species susceptible to the toxin. In this context, the aim of this work was to study the factors explaining the wide difference in susceptibility. In this work, we have evaluated the susceptibility of rabbit, horse and sheep erythrocytes relatively to their membrane lipid composition. The measurements of hemolytic activity revealed rabbit erythrocytes were the most susceptible to HlyA, followed by horse and sheep. Taking into account that oligomerization is required in the hemolytic process, we have studied binding and oligomerization of the toxin on ghost erythrocytes by fluorescence. The membrane fluidity was determined by Laurdan Generalized Polarization (GP) images monitored by two-photon fluorescence microscopy. The lipid composition was assessed by HPTLC and LCMS. The results showed that erythrocyte binding of the toxin was similar (approx. 30 %) for the three species investigated. While HlyA can oligomerize on all erythrocyte types but it oligomerizes more extensively on the rabbit erythrocytes, the only membranes that increase the GP value after the interaction with the toxin. On the other hand, the lipid composition of the three species is very different. The main differences are in the content of phosphatidylcholine and sphingomyelin and their molecular species composition. In conclusion, the composition of the membrane determines the degree of oligomerization of the toxin resulting in different susceptibilities toward HlyA, despite the presence or absence of receptor.