The Complex of Phosphatidylinositol 4,5-Bisphosphate and Calcium Ions Is Not Responsible for Ca2+-Induced Loss of Phospholipid Asymmetry in the Human Erythrocyte

A Study in Scott Syndrome, a Disorder of Calcium-Induced Phospholipid Scrambling

Edouard M. Bevers, Therese Wiedmer, Paul Comfurius, Ji Zhao, Edgar F. Smeets, Robert A. Schlegel, Alan J. Schroit, Harvey J. Weiss, Patrick Williamson, Robert F A Zwaal, Peter J. Sims

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

Elevation of cytoplasmic Ca2+ levels in human erythrocytes induces a progressive loss of membrane phospholipid asymmetry, a process that is impaired in erythrocytes from a patient with Scott syndrome. We show here that porcine erythrocytes are similarly incapable of Ca2+-induced redistribution of membrane phospholipids. Because a complex of phosphatidylinositol 4,5-bisphosphate (PIP2) and Ca2+ has been proposed as the mediator of enhanced transbilayer movement of lipids (J Biol Chem 269:6347,1994), these cell systems offer a unique opportunity for testing this mechanism. Analysis of both total PIP2 content and the metabolic-resistant pool of PIP2 that remains after incubation with Ca2+ ionophore showed no appreciable differences between normal and Scott erythrocytes. Moreover, porcine erythrocytes were found to have slightly higher levels of both total and metabolic-resistant PIP2 in comparison with normal human erythrocytes. Although loading of normal erythrocytes with exogenously added PIP2 gave rise to a Ca2+-induced increase in prothrombinase activity and apparent transbilayer movement of nitrobenzoxadiazolyl (NBD)-phospholipids, these PIP2-loaded cells were also found to undergo progressive Ca2+-dependent cell lysis, which seriously hampers interpretation of these data. Moreover, loading Scott cells with PIP2 did not abolish their impaired lipid scrambling, even in the presence of a Ca2+-ionophore. Finally, artificial lipid vesicles containing no PIP2 or 1 mole percent of PIP2 were indistinguishable with respect to transbilayer movement of NBD-phosphatidylcholine in the presence of Ca2+. Our findings suggest that Ca2+-induced redistribution of membrane phospholipids cannot simply be attributed to the steady-state concentration of PIP2, and imply that such lipid movement is regulated by other cellular processes.

Original languageEnglish (US)
Pages (from-to)1983-1991
Number of pages9
JournalBlood
Volume86
Issue number5
StatePublished - Sep 1 1995

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Phosphatidylinositols
Phospholipids
Erythrocytes
Ions
Calcium
Lipids
Ionophores
Membranes
Thromboplastin
Phosphatidylcholines
Swine
Scott Syndrome
monobasic calcium phosphate
Testing

ASJC Scopus subject areas

  • Hematology

Cite this

The Complex of Phosphatidylinositol 4,5-Bisphosphate and Calcium Ions Is Not Responsible for Ca2+-Induced Loss of Phospholipid Asymmetry in the Human Erythrocyte : A Study in Scott Syndrome, a Disorder of Calcium-Induced Phospholipid Scrambling. / Bevers, Edouard M.; Wiedmer, Therese; Comfurius, Paul; Zhao, Ji; Smeets, Edgar F.; Schlegel, Robert A.; Schroit, Alan J.; Weiss, Harvey J.; Williamson, Patrick; Zwaal, Robert F A; Sims, Peter J.

In: Blood, Vol. 86, No. 5, 01.09.1995, p. 1983-1991.

Research output: Contribution to journalArticle

Bevers, Edouard M. ; Wiedmer, Therese ; Comfurius, Paul ; Zhao, Ji ; Smeets, Edgar F. ; Schlegel, Robert A. ; Schroit, Alan J. ; Weiss, Harvey J. ; Williamson, Patrick ; Zwaal, Robert F A ; Sims, Peter J. / The Complex of Phosphatidylinositol 4,5-Bisphosphate and Calcium Ions Is Not Responsible for Ca2+-Induced Loss of Phospholipid Asymmetry in the Human Erythrocyte : A Study in Scott Syndrome, a Disorder of Calcium-Induced Phospholipid Scrambling. In: Blood. 1995 ; Vol. 86, No. 5. pp. 1983-1991.
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abstract = "Elevation of cytoplasmic Ca2+ levels in human erythrocytes induces a progressive loss of membrane phospholipid asymmetry, a process that is impaired in erythrocytes from a patient with Scott syndrome. We show here that porcine erythrocytes are similarly incapable of Ca2+-induced redistribution of membrane phospholipids. Because a complex of phosphatidylinositol 4,5-bisphosphate (PIP2) and Ca2+ has been proposed as the mediator of enhanced transbilayer movement of lipids (J Biol Chem 269:6347,1994), these cell systems offer a unique opportunity for testing this mechanism. Analysis of both total PIP2 content and the metabolic-resistant pool of PIP2 that remains after incubation with Ca2+ ionophore showed no appreciable differences between normal and Scott erythrocytes. Moreover, porcine erythrocytes were found to have slightly higher levels of both total and metabolic-resistant PIP2 in comparison with normal human erythrocytes. Although loading of normal erythrocytes with exogenously added PIP2 gave rise to a Ca2+-induced increase in prothrombinase activity and apparent transbilayer movement of nitrobenzoxadiazolyl (NBD)-phospholipids, these PIP2-loaded cells were also found to undergo progressive Ca2+-dependent cell lysis, which seriously hampers interpretation of these data. Moreover, loading Scott cells with PIP2 did not abolish their impaired lipid scrambling, even in the presence of a Ca2+-ionophore. Finally, artificial lipid vesicles containing no PIP2 or 1 mole percent of PIP2 were indistinguishable with respect to transbilayer movement of NBD-phosphatidylcholine in the presence of Ca2+. Our findings suggest that Ca2+-induced redistribution of membrane phospholipids cannot simply be attributed to the steady-state concentration of PIP2, and imply that such lipid movement is regulated by other cellular processes.",
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AU - Bevers, Edouard M.

AU - Wiedmer, Therese

AU - Comfurius, Paul

AU - Zhao, Ji

AU - Smeets, Edgar F.

AU - Schlegel, Robert A.

AU - Schroit, Alan J.

AU - Weiss, Harvey J.

AU - Williamson, Patrick

AU - Zwaal, Robert F A

AU - Sims, Peter J.

PY - 1995/9/1

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N2 - Elevation of cytoplasmic Ca2+ levels in human erythrocytes induces a progressive loss of membrane phospholipid asymmetry, a process that is impaired in erythrocytes from a patient with Scott syndrome. We show here that porcine erythrocytes are similarly incapable of Ca2+-induced redistribution of membrane phospholipids. Because a complex of phosphatidylinositol 4,5-bisphosphate (PIP2) and Ca2+ has been proposed as the mediator of enhanced transbilayer movement of lipids (J Biol Chem 269:6347,1994), these cell systems offer a unique opportunity for testing this mechanism. Analysis of both total PIP2 content and the metabolic-resistant pool of PIP2 that remains after incubation with Ca2+ ionophore showed no appreciable differences between normal and Scott erythrocytes. Moreover, porcine erythrocytes were found to have slightly higher levels of both total and metabolic-resistant PIP2 in comparison with normal human erythrocytes. Although loading of normal erythrocytes with exogenously added PIP2 gave rise to a Ca2+-induced increase in prothrombinase activity and apparent transbilayer movement of nitrobenzoxadiazolyl (NBD)-phospholipids, these PIP2-loaded cells were also found to undergo progressive Ca2+-dependent cell lysis, which seriously hampers interpretation of these data. Moreover, loading Scott cells with PIP2 did not abolish their impaired lipid scrambling, even in the presence of a Ca2+-ionophore. Finally, artificial lipid vesicles containing no PIP2 or 1 mole percent of PIP2 were indistinguishable with respect to transbilayer movement of NBD-phosphatidylcholine in the presence of Ca2+. Our findings suggest that Ca2+-induced redistribution of membrane phospholipids cannot simply be attributed to the steady-state concentration of PIP2, and imply that such lipid movement is regulated by other cellular processes.

AB - Elevation of cytoplasmic Ca2+ levels in human erythrocytes induces a progressive loss of membrane phospholipid asymmetry, a process that is impaired in erythrocytes from a patient with Scott syndrome. We show here that porcine erythrocytes are similarly incapable of Ca2+-induced redistribution of membrane phospholipids. Because a complex of phosphatidylinositol 4,5-bisphosphate (PIP2) and Ca2+ has been proposed as the mediator of enhanced transbilayer movement of lipids (J Biol Chem 269:6347,1994), these cell systems offer a unique opportunity for testing this mechanism. Analysis of both total PIP2 content and the metabolic-resistant pool of PIP2 that remains after incubation with Ca2+ ionophore showed no appreciable differences between normal and Scott erythrocytes. Moreover, porcine erythrocytes were found to have slightly higher levels of both total and metabolic-resistant PIP2 in comparison with normal human erythrocytes. Although loading of normal erythrocytes with exogenously added PIP2 gave rise to a Ca2+-induced increase in prothrombinase activity and apparent transbilayer movement of nitrobenzoxadiazolyl (NBD)-phospholipids, these PIP2-loaded cells were also found to undergo progressive Ca2+-dependent cell lysis, which seriously hampers interpretation of these data. Moreover, loading Scott cells with PIP2 did not abolish their impaired lipid scrambling, even in the presence of a Ca2+-ionophore. Finally, artificial lipid vesicles containing no PIP2 or 1 mole percent of PIP2 were indistinguishable with respect to transbilayer movement of NBD-phosphatidylcholine in the presence of Ca2+. Our findings suggest that Ca2+-induced redistribution of membrane phospholipids cannot simply be attributed to the steady-state concentration of PIP2, and imply that such lipid movement is regulated by other cellular processes.

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