TY - JOUR
T1 - An unrecognized function of cholesterol
T2 - Regulating the mechanism controlling membrane phospholipid asymmetry
AU - Arashiki, Nobuto
AU - Saito, Masaki
AU - Koshino, Ichiro
AU - Kamata, Kotoe
AU - Hale, John
AU - Mohandas, Narla
AU - Manno, Sumie
AU - Takakuwa, Yuichi
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/6/28
Y1 - 2016/6/28
N2 - An asymmetric distribution of phospholipids in the membrane bilayer is inseparable from physiological functions, including shape preservation and survival of erythrocytes, and by implication other cells. Aminophospholipids, notably phosphatidylserine (PS), are confined to the inner leaflet of the erythrocyte membrane lipid bilayer by the ATP-dependent flippase enzyme, ATP11C, counteracting the activity of an ATP-independent scramblase. Phospholipid scramblase 1 (PLSCR1), a single-transmembrane protein, was previously reported to possess scrambling activity in erythrocytes. However, its function was cast in doubt by the retention of scramblase activity in erythrocytes of knockout mice lacking this protein. We show that in the human erythrocyte PLSCR1 is the predominant scramblase and by reconstitution into liposomes that its activity resides in the transmembrane domain. At or below physiological intracellular calcium concentrations, total suppression of flippase activity nevertheless leaves the membrane asymmetry undisturbed. When liposomes or erythrocytes are depleted of cholesterol (a reversible process in the case of erythrocytes), PS quickly appears at the outer surface, implying that cholesterol acts in the cell as a powerful scramblase inhibitor. Thus, our results bring to light a previously unsuspected function of cholesterol in regulating phospholipid scrambling.
AB - An asymmetric distribution of phospholipids in the membrane bilayer is inseparable from physiological functions, including shape preservation and survival of erythrocytes, and by implication other cells. Aminophospholipids, notably phosphatidylserine (PS), are confined to the inner leaflet of the erythrocyte membrane lipid bilayer by the ATP-dependent flippase enzyme, ATP11C, counteracting the activity of an ATP-independent scramblase. Phospholipid scramblase 1 (PLSCR1), a single-transmembrane protein, was previously reported to possess scrambling activity in erythrocytes. However, its function was cast in doubt by the retention of scramblase activity in erythrocytes of knockout mice lacking this protein. We show that in the human erythrocyte PLSCR1 is the predominant scramblase and by reconstitution into liposomes that its activity resides in the transmembrane domain. At or below physiological intracellular calcium concentrations, total suppression of flippase activity nevertheless leaves the membrane asymmetry undisturbed. When liposomes or erythrocytes are depleted of cholesterol (a reversible process in the case of erythrocytes), PS quickly appears at the outer surface, implying that cholesterol acts in the cell as a powerful scramblase inhibitor. Thus, our results bring to light a previously unsuspected function of cholesterol in regulating phospholipid scrambling.
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U2 - 10.1021/acs.biochem.6b00407
DO - 10.1021/acs.biochem.6b00407
M3 - Article
C2 - 27267274
AN - SCOPUS:84976540344
VL - 55
SP - 3504
EP - 3513
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 25
ER -