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This Article Full Text Full Text (PDF) All Versions of this Article: 292/5/C1759    most recent 00158.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Akel, A. Articles by Lang, F. Search for Related Content PubMed PubMed Citation Articles by Akel, A. Articles by Lang, F.

GROWTH, DIFFERENTIATION, AND APOPTOSIS

Enhanced suicidal death of erythrocytes from gene-targeted mice lacking the Cl^–/HCO₃^– exchanger AE1

¹Department of Physiology, University of Tübingen, Tübingen, Germany; ²Institute of Physiology and Center for Integrative Human Physiology, University of Zürich, Zürich, Switzerland; ³Molecular and Vascular Medicine Unit and Renal Division, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts; and ⁴Zentrales Isotopenlabor/AG Biophysik, Saarland University, Saarbrücken, Germany

Submitted 16 April 2006 ; accepted in final form 19 January 2007

Genetic defects of anion exchanger 1 (AE1) may lead to spherocytic erythrocyte morphology, severe hemolytic anemia, and/or cation leak. In normal erythrocytes, osmotic shock, Cl^– removal, and energy depletion activate Ca²⁺-permeable cation channels with Ca²⁺-induced suicidal erythrocyte death, i.e., surface exposure of phosphatidylserine, cell shrinkage, and membrane blebbing, all features typical for apoptosis of nucleated cells. The present experiments explored whether AE1 deficiency favors suicidal erythrocyte death. Peripheral blood erythrocyte numbers were significantly smaller in gene-targeted mice lacking AE1 (AE1^–/– mice) than in their wild-type littermates (AE1^+/+ mice) despite increased percentages of reticulocytes (AE1^–/–: 49%, AE1^+/+: 2%), an indicator of enhanced erythropoiesis. Annexin binding, reflecting phosphatidylserine exposure, was significantly larger in AE1^–/–erythrocytes/reticulocytes (10%) than in AE1^+/+ erythrocytes (1%). Osmotic shock (addition of 400 mM sucrose), Cl^– removal (replacement with gluconate), or energy depletion (removal of glucose) led to significantly stronger annexin binding in AE1^–/– erythrocytes/reticulocytes than in AE1^+/+ erythrocytes. The increase of annexin binding following exposure to the Ca²⁺ ionophore ionomycin (1 µM) was, however, similar in AE1^–/– and in AE1^+/+ erythrocytes. Fluo3 fluorescence revealed markedly increased cytosolic Ca²⁺ permeability in AE1^–/– erythrocytes/reticulocytes. Clearance of carboxyfluorescein diacetate succinimidyl ester-labeled erythrocytes/reticulocytes from circulating blood was more rapid in AE1^–/– mice than in AE1^+/+ mice and was accelerated by ionomycin treatment in both genotypes. In conclusion, lack of AE1 is associated with enhanced Ca²⁺ entry and subsequent scrambling of cell membrane phospholipids.

annexin; cell volume; osmolarity; phosphatidylserine; energy depletion