title: Stimulation of Suicidal Erythrocyte Death by Phosphatase Inhibitor Calyculin A.
abstract: OBJECTIVE
  The serine/threonine protein phosphatase 1 and 2a inhibitor Calyculin A may trigger suicidal death or apoptosis of tumor cells. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include increase of cytosolic Ca2+ activity ([Ca2+] i). Eryptosis is fostered by activation of staurosporine sensitive protein kinase C, SB203580 sensitive p38 kinase, and D4476 sensitive casein kinase. Eryptosis may further involve zVAD sensitive caspases. The present study explored, whether Calyculin A induces eryptosis and, if so, whether its effect requires Ca2+ entry, kinases and/or caspases Methods: Phosphatidylserine exposure at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter, and [Ca2+] i from Fluo-3 fluorescence, as determined by flow cytometry.
  
  
  RESULTS
  A 48 hours exposure of human erythrocytes to Calyculin A (≥ 2.5 nM) significantly increased the percentage of annexin-V-binding cells, significantly decreased forward scatter and significantly increased Fluo-3 fluorescence. The effect of Calyculin A on annexin-V-binding was significantly blunted by removal of extracellular Ca2+, by staurosorine (1 µM), SB203580 (2 µM), D4476 (10 µM), and zVAD (10 µM).
  
  
  CONCLUSIONS
  Calyculin A triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part requiring Ca2+ entry, kinase activity and caspase activation.
authors.affiliation: Department of Cardiology, Vascular Medicine and Physiology, Eberhard-Karls-University of Tuebingen, Tuebingen, Germany.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Almasry
authors.forename: Mohamed
authors.initials: M
authors.lastname: Jemaà
authors.forename: Morena
authors.initials: M
authors.lastname: Mischitelli
authors.forename: Caterina
authors.initials: C
authors.lastname: Faggio
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D002118:Calcium / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D000072817:Eryptosis / Q000187:drug effects*; D006801:Humans; D008387:Marine Toxins; D010080:Oxazoles / Q000494:pharmacology*; D010718:Phosphatidylserines / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D012542:Scattering, Radiation
chemical_list: D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D010718:Phosphatidylserines; C059041:calyculin A; D010744:Phosphoric Monoester Hydrolases; D002118:Calcium