Molecular species of glycerophospholipids and sphingomyelins of human erythrocytes: Improved method of analysis

Myher, J. J.; Kuksis, A.; Pind, Steven

doi:10.1007/bf02535147

Cited by 128 publications

(74 citation statements)

References 33 publications

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“…In particular, the outer leaflet of the plasma membrane is rich in phosphatidylcholine and sphingolipids, while the leaflet facing the cytoplasm is rich in phosphatidylethanolamine, phosphatidylserine and other, mostly anionic, phospholipids [82]. An asymmetry in the unsaturation of their fatty-acyl chains runs parallel: the lipids enriched in the outer surface have an abundance of saturated chains, while the inner surface species are characteristically poly-unsaturated [83]. Given that the phospholipids characteristic of the exofacial surface associate with sterols several times more strongly than do those enriched in the endofacial leaflet [10,20,84], we might expect that the mole fraction of the sterol will be significantly higher in the outer than the inner leaflet of a given plasma membrane bilayer.…”

Section: Cholesterol Activity In the Two Bilayer Leafletsmentioning

confidence: 99%

Cholesterol homeostasis and the escape tendency (activity) of plasma membrane cholesterol

Lange

Steck

2008

Progress in Lipid Research

142

190

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We review evidence that sterols can form stoichiometric complexes with certain bilayer phospholipids, and sphingomyelin in particular. These complexes appear to be the basis for the formation of condensed and ordered liquid phases, (micro)domains and/or rafts in both artificial and biological membranes. The sterol content of a membrane can exceed the complexing capacity of its phospholipids. The excess, uncomplexed membrane sterol molecules have a relatively high escape tendency, also referred to as fugacity or chemical activity (and, here, simply activity). Cholesterol is also activated when certain membrane intercalating amphipaths displace it from the phospholipid complexes. Active cholesterol projects from the bilayer and is therefore highly susceptible to attack by cholesterol oxidase. Similarly, active cholesterol rapidly exits the plasma membrane to extracellular acceptors such as cyclodextrin and high-density lipoproteins. For the same reason, the pool of cholesterol in the ER (endoplasmic reticulum) increases sharply when cell surface cholesterol is incremented above the physiological set-point; i.e., equivalence with the complexing phospholipids. As a result, the escape tendency of the excess cholesterol not only returns the plasma membrane bilayer to its set point but also serves as a feedback signal to intracellular homeostatic elements to down-regulate cholesterol accretion.

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Section: Cholesterol Activity In the Two Bilayer Leafletsmentioning

confidence: 99%

Cholesterol homeostasis and the escape tendency (activity) of plasma membrane cholesterol

Lange

Steck

2008

Progress in Lipid Research

142

190

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“…Because the predominant fatty acid found at the sn-1 position of PC of human RBCs is C16:0 (1), we chose 1-(C16:0)-lysoPC as the lysoPC acceptor for additional experiments. The diacyl subclass of PC accounts for more than 93% of the PC molecular species in RBCs, and the major acyl species found at the sn-2 position of diacyl-PC in RBC membranes are C16:0 (5%), C18:1 (29%), C18:2 (42%), and C20:4 (9%) (1). At a concentration of 16 M acyl-CoA, transfer rates were highest for the precursor of the two most abundant acyl species (C18:1-CoA and C18:2-CoA), followed by the polyunsaturated C20:4-CoA and the saturated C16:0-CoA (Fig.…”

Section: (Lane R) and Friend Cells (Lane Fc) (See Materials And Methomentioning

confidence: 99%

“…Its molecular composition comprises more than 250 different glycerophospholipid molecular species (1). This enucleated cell lacks internal organelles and de novo lipid synthesis.…”

mentioning

confidence: 99%

“…To maintain the integrity of its membrane, lipid molecules are continuously renewed. Different classes of fatty acids are found at the two positions of the glycerol backbone of phospholipids, and their distribution is heterogeneous (1). The sn-1 position of glycerophospholipids is mainly occupied by saturated acylchains 16-18 carbon atoms long, whereas a variety of unsaturated fatty acylchains are found at the sn-2 position.…”

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confidence: 99%

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Mammalian acyl-CoA:lysophosphatidylcholine acyltransferase enzymes

Soupène¹,

Fyrst²,

Kuypers³

2008

Proc. Natl. Acad. Sci. U.S.A.

103

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The mammalian RBC lacks de novo lipid synthesis but maintains its membrane composition by rapid turnover of acyl moieties at the sn-2 position of phospholipids. Plasma-derived fatty acids are esterified to acyl-CoA by acyl-CoA synthetases and transferred to lysophospholipids by acyl-CoA:lysophospholipid acyltransferases. We report the characterization of three lysophosphatidylcholine (lysoPC) acyltransferases (LPCATs), products of the AYTL1, -2, and -3 genes. These proteins are three members of a LPCAT family, of which all three genes are expressed in an erythroleukemic cell line. Aytl2 mRNA was detected in mouse reticulocytes, and the presence of the product of the human ortholog was confirmed in adult human RBCs. The three murine Aytl proteins generated phosphatidylcholine from long-chain acyl-CoA and lysoPC when expressed in Escherichia coli membranes. Spliced variants of Aytl1, affecting a conserved catalytic motif, were identified. Calcium and magnesium modulated LPCAT activity of both Aytl1 and -2 proteins that exhibit EF-hand motifs at the C terminus. Characterization of the product of the Aytl2 gene as the phosphatidylcholine reacylating enzyme in RBCs represents the identification of a plasma membrane lysophospholipid acyltransferase and establishes the function of a LPCAT protein.phosphatidylcholine ͉ RBC ͉ AYTL2

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“…1-Palmitoyl-2-linoleoyl-PC, 1-palmitoyl-2-arachidonoyl-PC, and dipalmitoyl-PC exhibited half-times of inward equilibration of 2.9, 9.7, and 26.3 h, respectively (8). These PC species account for 26.9, 5.1, and 4.6% of total human erythrocyte PC (60), suggesting that the half-time of 1-palmitoyl-2-linoleoyl-PC approaches best the apparent inward translocation of total PC. Discrepancies in the determined time scale of apparent PC inward translocation in this study and those in the literature may be the result of differences in the cell surface assays.…”

Section: Discussionmentioning

confidence: 94%

Natural Phosphatidylcholine Is Actively Translocated across the Plasma Membrane to the Surface of Mammalian Cells

Kälin

Fernandes

Hrafnsdóttir

et al. 2004

Journal of Biological Chemistry

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The cell surface of eukaryotic cells is enriched in choline phospholipids, whereas the aminophospholipids are concentrated at the cytosolic side of the plasma membrane by the activity of one or more P-type ATPases. Lipid translocation has been investigated mostly by using short chain lipid analogs because assays for endogenous lipids are inherently complicated. In the present paper, we optimized two independent assays for the translocation of natural phosphatidylcholine (PC) to the cell surface based on the hydrolysis of outer leaflet phosphoglycerolipids by exogenous phospholipase A 2 and the exchange of outer leaflet PC by a transfer protein. We report that PC reached the cell surface in the absence of vesicular traffic by a pathway that involved translocation across the plasma membrane. In erythrocytes, PC that was labeled at the inside of the plasma membrane was translocated to the cell surface with a half-time of 30 min. This translocation was probably mediated by an ATPase, because it required ATP and was vanadate-sensitive. The inhibition of PC translocation by glibenclamide, an inhibitor of various ATP binding cassette transporters, and its reduction in erythrocytes from both Abcb1a/1b and Abcb4 knockout mice, suggest the involvement of ATP binding cassette transporters in natural PC cell surface translocation. The relative importance of the outward translocation of PC as compared with the well characterized fast inward translocation of phosphatidylserine for the overall asymmetric phospholipid organization in plasma membranes remains to be established.The distribution of lipids across the eukaryotic plasma membrane bilayer is asymmetric with the choline phospholipids sphingomyelin and phosphatidylcholine (PC) 1 at the cell surface and the aminophospholipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) at the inside (1, 2). PS and PE are continuously translocated from the exoplasmic to the cytoplasmic leaflet of cellular membranes by proteins belonging to a subfamily of P-type ATPases (3, 4). Inward translocation of PS is essential to prevent PS cell surface signaling, which induces blood coagulation and serves as a signal for cell-cell recognition, e.g. the removal of apoptotic cells by macrophages. An additional function of lipid translocation has emerged recently. Evidence from mammalian and yeast cells suggests that ATP-dependent inward translocation of phospholipids by the aminophospholipid translocase affects membrane curvature and is a, or the, driving force for the formation of endocytic vesicles at the plasma membrane (4 -6). The fact that yeast expresses five P-type ATPase family members in different compartments of the exocytic and endocytic transport pathways suggests the possibility that all membrane budding from sphingolipid-and cholesterol-rich membranes depends on the mass translocation of membrane phospholipids.The bulk membrane phospholipid in mammalian cells is PC, which constitutes 25-50 mol % of the membrane lipids. However, it is unclear if cells possess mechanisms for ...

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Molecular species of glycerophospholipids and sphingomyelins of human erythrocytes: Improved method of analysis

Cited by 128 publications

References 33 publications

Cholesterol homeostasis and the escape tendency (activity) of plasma membrane cholesterol

Cholesterol homeostasis and the escape tendency (activity) of plasma membrane cholesterol

Mammalian acyl-CoA:lysophosphatidylcholine acyltransferase enzymes

Natural Phosphatidylcholine Is Actively Translocated across the Plasma Membrane to the Surface of Mammalian Cells

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