title: Characterization of the phosphatidylserine-exposing subpopulation of sickle cells.
abstract: Phosphatidylserine (PS), exclusively present in the inner monolayer of the normal red blood cell (RBC) membrane, is exposed in subpopulations of sickle cells. PS-exposing RBCs were found predominantly among the densest and the very light sickle cells. Within the light RBC fraction, PS exposure was found on reticulocytes, transferrin receptor-expressing reticulocytes, and mature RBCs. The last subset contained low-density valinomycin-resistant RBCs, previously shown to have high Na(+) and low K(+) content. This subpopulation contained the highest percentage of PS-exposing cells. The PS-exposing sickle cells did not show the sustained high cytosolic Ca(++) levels that have been shown to activate scramblase activity. Data from this study indicate that PS exposure can occur at different stages in the life of the sickle RBC and that it correlates with the loss of aminophospholipid translocase activity, the only common denominator of the PS-exposing cells. The additional requirement of scramblase activation may occur during transient increases in cytosolic Ca(++). (Blood. 2001;98:860-867)
authors.affiliation: Children's Hospital Oakland Research Institute, 5700 Martin Luther King Jr Way, Oakland, CA 94609, USA. kdejong@chori.org
authors.forename: K
authors.initials: K
authors.lastname: de Jong
authors.forename: S K
authors.initials: SK
authors.lastname: Larkin
authors.forename: L A
authors.initials: LA
authors.lastname: Styles
authors.forename: R M
authors.initials: RM
authors.lastname: Bookchin
authors.forename: F A
authors.initials: FA
authors.lastname: Kuypers
mesh_terms: D000755:Anemia, Sickle Cell / Q000097:blood* / Q000201:enzymology / Q000473:pathology*; D017304:Annexin A5 / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000145:classification / Q000201:enzymology / Q000648:ultrastructure; D006801:Humans; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D010718:Phosphatidylserines / Q000097:blood / Q000737:chemistry / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins; D011990:Receptors, Transferrin / Q000032:analysis; D012156:Reticulocytes / Q000145:classification / Q000201:enzymology / Q000648:ultrastructure
chemical_list: D017304:Annexin A5; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D010718:Phosphatidylserines; D049294:Phospholipid Transfer Proteins; D011990:Receptors, Transferrin; D002118:Calcium