title: Stimulation of erythrocyte cell membrane scrambling by mushroom tyrosinase.
abstract: BACKGROUND
  Mushroom tyrosinase, a copper containing enzyme, modifies growth and survival of tumor cells. Mushroom tyrosinase may foster apoptosis, an effect in part due to interference with mitochondrial function. Erythrocytes lack mitochondria but are able to undergo apoptosis-like suicidal cell death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine-exposure at the erythrocyte surface. Signaling involved in the triggering of eryptosis include increase of cytosolic Ca2+-activity ([Ca2+]i) and activation of sphingomyelinase with subsequent formation of ceramide. The present study explored, whether tyrosinase stimulates eryptosis.
  
  
  METHODS
  Cell volume has been estimated from forward scatter, phosphatidylserine-exposure from annexin V binding, [Ca2+]i from Fluo3-fluorescence, and ceramide abundance from binding of fluorescent antibodies in flow cytometry.
  
  
  RESULTS
  A 24 h exposure to mushroom tyrosinase (7 U/mL) was followed by a significant increase of [Ca2+]i, a significant increase of ceramide abundance, and a significant increase of annexin-V-binding. The annexin-V-binding following tyrosinase treatment was significantly blunted but not abrogated in the nominal absence of extracellular Ca2+. Tyrosinase did not significantly modify forward scatter.
  
  
  CONCLUSIONS
  Tyrosinase triggers cell membrane scrambling, an effect, at least partially, due to entry of extracellular Ca2+ and ceramide formation.
authors.affiliation: Department of Physiology, Eberhard-Karls-University of Tuebingen, Gmelinstr. 5, 72076 Tübingen, Germany. leonie.frauenfeld9@gmail.com.
authors.forename: Leonie
authors.initials: L
authors.lastname: Frauenfeld
authors.affiliation: Department of Physiology, Eberhard-Karls-University of Tuebingen, Gmelinstr. 5, 72076 Tübingen, Germany. kossai.z@gmail.com.
authors.forename: Kousi
authors.initials: K
authors.lastname: Alzoubi
authors.affiliation: Department of Physiology, Eberhard-Karls-University of Tuebingen, Gmelinstr. 5, 72076 Tübingen, Germany. dr.magd81@hotmail.com.
authors.forename: Majed
authors.initials: M
authors.lastname: Abed
authors.affiliation: Department of Physiology, Eberhard-Karls-University of Tuebingen, Gmelinstr. 5, 72076 Tübingen, Germany. florian.lang@uni-tuebingen.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000363:Agaricales / Q000201:enzymology*; D017209:Apoptosis / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D048429:Cell Size / Q000187:drug effects; D002518:Ceramides / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000187:drug effects* / Q000378:metabolism; D014442:Monophenol Monooxygenase / Q000494:pharmacology*; D010718:Phosphatidylserines / Q000378:metabolism*
chemical_list: D002518:Ceramides; D010718:Phosphatidylserines; D014442:Monophenol Monooxygenase; D002118:Calcium