Membrane properties that determine the susceptibility of erythrocytes to HlyA of E.coli

SABINA MATÉ; VANESA HERLAX; LAURA BAKÁS

Buzios, Brasil

Congreso; VII Iberoamerican Congress of Biophysics; 2009

Sociedad Iberoamericana de Biofisica

á-hemolysin (HlyA) is an exotoxin secreted by some pathogenic strains of E.coli that causes lyses of several mammalian cells, including erythrocytes of different species. Although the toxin causes the lyses of liposome composed of pure lipids, some studies demonstrated the presence of toxin receptors in several target cells. In horse erythrocytes, glycophorin was the protein characterized as the receptor for HlyA. On the other hand, Bauer and Welch have previously found that HlyA binds nonspecifically to rabbit erythrocytes. In this context, the aim of this work was to study the membrane properties that determine the susceptibility of erythrocytes to HlyA in different species (rabbit, horse and sheep) to HlyA. These erythrocytes present differences concerning lipid composition and protein profile. The hemolytic activity demonstrated that Rabbit erythrocytes were the most susceptible to HlyA, followed by sheep and horse. To elucidate the cause for this difference we studied: the membrane fluidity by Laurdan Generalized Polarization (GP) images taken in a two-photon Fluorescence Microscope, the glycophorin content analyzed by western blot and the lipid composition by HPTLC and LCMS. The results showed that rabbit erythrocytes are the ones that present the highest concentration of the receptor and present an intermediate ratio of Chol/SM. Moreover, these erythrocytes showed a decrease in their membrane fluidity after the interaction with the toxin. The final conclusion is that the properties of membranes that determines the susceptibility of erythrocytes to HlyA depends of both the protein receptor and the lipidic environment.