Induction of erythrocyte microvesicles by Escherichia Coli Alpha hemolysin

STRACK, KAREN; LAURI, NATALIA; MATÉ, SABINA MARÍA; SARALEGUI, ANDRÉS; MUÑOZ-GARAY, CARLOS; SCHWARZBAUM, PABLO J.; HERLAX, VANESA

BIOCHEMICAL JOURNAL

PORTLAND PRESS LTD

Año: 2019 vol. 476 p. 3455 - 3473

0264-6021

Alpha hemolysin (HlyA) is the major virulence factor of uropathogenic Escherichia coli(UPEC) strains. Once in circulation, a low concentration of the toxin induces an increasein intracellular calcium that activates calpains ? which proteolyse cytoskeleton proteins ?and also favours the exposure of phosphatidylserine (PS) in the outer leaflet of erythrocytemembranes. All these events are considered part of eryptosis, as well as the delivery ofmicrovesicles (MVs). Within this context, we studied the delivery of MVs by erythrocytestreated with sublytic concentrations of HlyA and demonstrated that HlyA-treated erythrocytessecrete MVs of diameter ∼200 nm containing HlyA and PS by a mechanism involvingan increment of intracellular calcium concentration and purinergic receptor activation.Despite the presence of toxin in their membrane, HlyA-MVs are not hemolytically activeand do not induce ATP release in untreated erythrocytes, thus suggesting that the deliveryof HlyA-MVs might act as a protective mechanism on the part of erythrocytes thatremoves the toxin from the membrane to prevent the spread of infection. Although erythrocyteshave been found to eliminate denatured hemoglobin and several membrane proteinsby shedding MVs, the present work has revealed for the first time that an exogenousprotein, such as a toxin, is eliminated by this process. This finding sheds light on themechanism of action of the toxin and serves to further elucidate the consequences ofUPEC infection in patients exhibiting HlyA-related diseases.