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Ca2+ sensitivity of phospholipid scrambling in human red cell ghosts.
- Source :
-
Cell calcium [Cell Calcium] 1999 Apr; Vol. 25 (4), pp. 313-20. - Publication Year :
- 1999
-
Abstract
- The phospholipids in plasma membranes of erythrocytes, as well as platelets, lymphocytes and other cells are asymmetrically distributed, with sphingomyelin and phosphatidylcholine residing predominantly in the outer leaflet of the bilayer, and phosphatidylserine and phosphatidylethanolamine in the inner leaflet. It is known that Ca2+ can disrupt the phospholipid asymmetry by activation of a protein known as phospholipid scramblase, which affects bidirectional phospholipid movement in a largely non-selective manner. As Ca2+ also inhibits aminophospholipid translocase, whose Mg(2+)-ATPase activity is responsible for active translocation of aminophospholipids from the outer to the inner leaflet, it is important to accurately determine the sensitivity of scramblase to intracellular free Ca2+. In the present study we have utilized the favourable Kd of Mag-fura-2 for calcium in the high micromolar range to determine free Ca2+ levels associated with lipid scrambling in resealed human red cell ghosts. The Ca2+ sensitivity was measured in parallel to the translocation of a fluorescent-labelled lipid incorporated into the ghost bilayer. The phospholipid scrambling was found to be half-maximally activated at 63-88 microM free intracellular Ca2+. The wider applicability of the method and the physiological implications of the calcium sensitivity determined is discussed.
- Subjects :
- 4-Chloro-7-nitrobenzofurazan analogs & derivatives
4-Chloro-7-nitrobenzofurazan metabolism
Calcimycin pharmacology
Carrier Proteins metabolism
Erythrocyte Membrane drug effects
Fluorescent Dyes analysis
Fura-2 analogs & derivatives
Fura-2 analysis
Humans
Ionophores pharmacology
Membrane Proteins metabolism
Phosphatidylcholines metabolism
Calcium metabolism
Erythrocyte Membrane metabolism
Phospholipid Transfer Proteins
Phospholipids metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0143-4160
- Volume :
- 25
- Issue :
- 4
- Database :
- MEDLINE
- Journal :
- Cell calcium
- Publication Type :
- Academic Journal
- Accession number :
- 10456228
- Full Text :
- https://doi.org/10.1054/ceca.1999.0029