title: The cholesterol content of the erythrocyte membrane is an important determinant of phosphatidylserine exposure.
abstract: Maintenance of the asymmetric distribution of phospholipids across the plasma membrane is a prerequisite for the survival of erythrocytes. Various stimuli have been shown to induce scrambling of phospholipids and thereby exposure of phosphatidylserine (PS). In two types of patients, both with aberrant plasma cholesterol levels, we observed an aberrant PS exposure in erythrocytes upon stimulation. We investigated the effect of high and low levels of cholesterol on the ATP-dependent flippase, which maintains phospholipid asymmetry, and the ATP-independent scrambling activity, which breaks down phospholipid asymmetry. We analyzed erythrocytes of a patient with spur cell anemia, characterized by elevated plasma cholesterol, and the erythrocytes of Tangier disease patients with very low levels of plasma cholesterol. In normal erythrocytes, loaded with cholesterol or depleted of cholesterol in vitro, the same analyses were performed. Changes in the cholesterol/phospholipid ratio of erythrocytes had marked effects on PS exposure upon cell activation. Excess cholesterol profoundly inhibited PS exposure, whereas cholesterol depletion led to increased PS exposure. The activity of the ATP-dependent flippase was not changed, suggesting a major influence of cholesterol on the outward translocation of PS. The effects of cholesterol were not accompanied by eminent changes in cytoskeletal and membrane proteins. These findings emphasize the importance of cholesterol exchange between circulating plasma and the erythrocyte membrane as determinant for phosphatidylserine exposure in erythrocytes.
authors.affiliation: Laboratory of Red Blood Cell Diagnostics, Dept. of Blood Cell Research, Sanquin Blood Supply Foundation, Amsterdam, The Netherlands. r.vanzwieten@sanquin.nl
authors.forename: Rob
authors.initials: R
authors.lastname: van Zwieten
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Bochem
authors.forename: Petra M
authors.initials: PM
authors.lastname: Hilarius
authors.forename: Robin
authors.initials: R
authors.lastname: van Bruggen
authors.forename: Ferry
authors.initials: F
authors.lastname: Bergkamp
authors.forename: G Kees
authors.initials: GK
authors.lastname: Hovingh
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Verhoeven
mesh_terms: D009327:4-Chloro-7-nitrobenzofurazan / Q000031:analogs & derivatives / Q000378:metabolism; D000743:Anemia, Hemolytic / Q000097:blood; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D061207:Calcium Ionophores / Q000494:pharmacology; D002784:Cholesterol / Q000378:metabolism* / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000737:chemistry / Q000378:metabolism*; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D010713:Phosphatidylcholines / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D013049:Spectrin / Q000378:metabolism; D013631:Tangier Disease / Q000097:blood; D013997:Time Factors
chemical_list: C078632:1-acyl-2-(12-((7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)dodecanoyl)phosphatidylcholine; D001457:Anion Exchange Protein 1, Erythrocyte; D061207:Calcium Ionophores; D010713:Phosphatidylcholines; D010718:Phosphatidylserines; D010743:Phospholipids; D013049:Spectrin; D000001:Calcimycin; D002784:Cholesterol; D009327:4-Chloro-7-nitrobenzofurazan; D002118:Calcium