title: Induction of eryptosis by low concentrations of E. coli alpha-hemolysin.
abstract: Uropathogenic strains of Escherichia coli deliver the toxin alpha-hemolysin (HlyA) to optimize the host environment for the spread of infection. It was reported that at high concentrations, the toxin forms pores in eukaryotic membranes, leading to cell lysis, while lower concentrations have appeared to interfere with host-cell-signaling pathways causing cell death by apoptosis. Nevertheless, what is not clear is how often HlyA reaches levels that are high enough to lyse host target cells during the course of an infection. In the present investigation, we demonstrate that a low toxin concentration induces the suicidal death of erythrocytes (eryptosis), the major cell type present in blood. Eryptosis is triggered both by an increment in intracellular calcium and by ceramide. Since we have previously demonstrated that a low concentration of HlyA induces an increase in intraerythrocyte calcium, in the present experiments we have shown that this ion activates calpains, which hydrolyze skeleton proteins such as spectrin, ankyrin, protein 4.1 and the electrophoretic Band-3 species, thus resulting in morphologic changes in the erythrocytes. We furthermore observed that a low toxin concentration induced the activation of endogenous sphingomyelinases that in turn increased the amount of ceramide in erythrocyte membranes. Both spectrin proteolysis and ceramide formation may cause the exposure of phosphatidylserine on the membrane so as to trigger a macrophage engulfment of the erythrocyte. By this means eryptosis may be an advantageous mechanism for removing defective erythrocytes before hemolysis.
authors: Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina.
authors: Fernanda Carrizo
authors: FC
authors: Velásquez
authors: Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina.
authors: Sabina
authors: S
authors: Maté
authors: Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 y 115, 1900 La Plata, Argentina.
authors: Laura
authors: L
authors: Bakás
authors: Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT-La Plata, CONICET, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, 1900 La Plata, Argentina. Electronic address: vherlax@med.unlp.edu.ar.
authors: Vanesa
authors: V
authors: Herlax
mesh_terms: D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism; D017487:Ankyrins / Q000378:metabolism; D001427:Bacterial Toxins / Q000494:pharmacology; D002154:Calpain / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000494:pharmacology*; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D006868:Hydrolysis; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D013049:Spectrin / Q000378:metabolism; D013997:Time Factors
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D017487:Ankyrins; D001427:Bacterial Toxins; D002518:Ceramides; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C036507:Hlya protein, E coli; D013049:Spectrin; D002154:Calpain
keywords: Cytoskeleton; Endogenous sphingomyelinase; Eryptosis; RTX toxin; μ-Calpains