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PubMed1993

Detection of anti-phospholipid and anti-DNA antibodies and their idiotypes in newborns of mothers with anti-phospholipid syndrome and SLE.

The titers, isotypes and idiotypes of antiphospholipid and anti-dsDNA antibodies were determined in seven pairs of mothers with antiphospholipid syndrome (APLS) and their offspring, in 11 pairs of SLE mothers and their matched infants and in seven respective pairs of healthy subjects. In addition, maternal as well as fetal sera were evaluated for the presence of anti-SSA (Ro), anti-SSB (La) and anti-70 kd RNP autoantibodies. In the sera from APLS patients, as well as in the sera from their offspring, the mean antibody titer of IgG aCL was found to be significantly higher then the corresponding value in the control group (P < 0.01). Highly significant increased titers of IgG anti-DNA antibodies were found in the sera of SLE mothers and their matched offspring (P < 0.0008). The prevalence of anti-SSA, anti-SSA, and anti-70Kd RNP antibodies was lower then that of antiphospholipid and anti-dsDNA antibodies. Only one of the respective offspring had increased levels of these antibodies. The quantity of maternal antibodies transferred to the fetus was depended on their concentration in the maternal circulation, as well as on their type and specificity. Follow-up of newborn sera showed a progressive decrease in the antiphospholipid antibody titers during 3 months. After 6 months it was undetected. Our results point to a transplacental transfer of aCL and anti-DNA antibodies, a phenomenon which is not necessarily associated with respective clinical manifestations, in contrast to the classical humoral mediated autoimmune diseases (e.g. myasthenia gravis).

Adult↗
PubMed1991

Protein kinase C isotypes and signaling in neutrophils. Differential substrate specificities of a translocatable calcium- and phospholipid-dependent beta-protein kinase C and a phospholipid-dependent protein kinase which is inhibited by long chain fatty acyl coenzyme A.

Neutrophils possess a classical Ca2+, phosphatidyl serine (PS) and diglyceride (DG)-dependent protein kinase C (beta-PKC) which was translocatable from cytosol to membrane in response to elevated Ca2+ in the physiologic range or to pretreatment with phorbol myristate acetate (PMA). The translocatable beta-PKC was purified from neutrophil membranes prepared in the presence of Ca2+, eluted with EGTA and subjected to hydroxyapatite chromatography. An 80-kDa protein possessing Ca/DG/PS-dependent histone phosphorylating activity was recognized by a monoclonal antibody to beta-PKC but not to alpha-PKC or gamma-PKC. A cytosolic kinase activity remaining after Ca(2+)-induced translocation of beta-PKC was dependent on PS and DG but did not require Ca2+. This novel Ca(2+)-independent, PS/DG-dependent kinase, termed nPKC, eluted from hydroxyapatite between alpha-PKC and beta-PKC, ran as a 76-kDa band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and was reactive to a polyclonal consensus antibody but not to monoclonal antibodies to alpha-PKC, beta-PKC, or gamma-PKC. Long chain fatty acyl-CoA, but not the corresponding free fatty acids, inhibited nPKC in the 1-10 microM range. The chemotactic peptide fMet-Leu-Phe triggered prompt but transient increases in neutrophil long chain fatty acid acyl-CoA, suggesting that nPKC is regulated by fatty acyl-CoA as well as DG during neutrophil activation. Purified beta-PKC phosphorylated a number of cytosolic proteins in a Ca(2+)-dependent manner, including a major 47-kDa cytosolic protein, which may be implicated in superoxide anion generation. In contrast, nPKC did not phosphorylate the 47-kDa protein, but phosphorylated numerous cytosolic proteins in a Ca(2+)-independent manner, including a 66-kDa protein which was not phosphorylated by beta-PKC. Differences in location, substrate specificity, and cofactor dependence between nPKC and beta-PKC suggest these kinases may play selective roles in the activation sequence of the neutrophil.

Acyl Coenzyme A↗
PubMed1990

Peptide inhibitors of enveloped virus infection inhibit phospholipid vesicle fusion and Sendai virus fusion with phospholipid vesicles.

Small hydrophobic peptides that are capable of inhibiting Sendai virus infection of cells (Richardson, C. D., Scheid, A., and Choppin, P. W. (1980) Virology 105, 205-222) are also capable of inhibiting membrane fusion in a pure lipid vesicle system. Large unilamellar vesicles of N-methyl dioleoylphosphatidylethanolamine containing encapsulated 1-aminonaphthalene-3,6,8-trisulfonic acid and/or p-xylene bis (pyridinium bromide) were formed by extrusion. Vesicle fusion (contents mixing) and leakage were then monitored with the 1-aminonaphthalene-3,6,8-trisulfonic acid/p-xylene bis(pyridinium bromide) fluorescence assay. Sendai virus fusion with lipid vesicles was measured by following the relief of fluorescence quenching of virus labeled with octadecylrhodamine B chloride, a lipid mixing assay for fusion. The efficiency with which the peptides carbobenzoxy-D-Phe-L-PheGly, carbobenzoxy-L-Phe-L-Tyr, and carbobenz-oxy-Gly-L-Phe inhibit fusion of N-methyl dioleoyl-phosphatidylethanolamine large unilamellar vesicles directly paralleled their previously known effectiveness in blocking virus infectivity of cultured cells. In addition, above a certain concentration threshold, the inhibitory peptides decreased the initial rate of leakage from lipid vesicles. The inhibition by these peptides of virus-vesicle fusion followed the same order of potency as for vesicle-vesicle fusion. The observation of the same relative potency of these peptides toward inhibition of virus-cell infection, and virus-vesicle and vesicle-vesicle membrane fusion suggested that these peptides inhibited virus-cell infection by inhibiting the ability of the virus to fuse with the cell. Furthermore, these results suggest that the mechanism of inhibition of all three fusion events may have steps in common.

Amino Acid Sequence↗
PubMed1995

Regulation of murine plasma phospholipid transfer protein activity and mRNA levels by lipopolysaccharide and high cholesterol diet.

Plasma phospholipid transfer protein mediates the net movement of phospholipids between lipoproteins and between lipid bilayers and high density lipoprotein. In this study, the mouse phospholipid transfer protein cDNA was cloned by reverse transcription polymerase chain reactions based on the cDNA sequence of human phospholipid transfer protein. The predicted amino acid sequence of mouse phospholipid transfer protein shows the protein to be 476 amino acids long and to have a sequence identity of 83% with that of human phospholipid transfer protein. Mouse plasma phospholipid transfer protein activity is 1.5-2 times that of human plasma phospholipid transfer protein activity. As in humans, mouse peripheral tissues displayed a higher abundance of phospholipid transfer protein mRNA than observed in central organs. The order of phospholipid transfer protein mRNA expression was as follows: lung > adipose tissue, placenta, testis > brain > muscle, heart, liver. We examined the regulation of phospholipid transfer protein expression by dietary cholesterol and by bacterial lipopolysaccharide. A high fat, high cholesterol diet caused a significant increase (35%) in plasma phospholipid transfer protein activity and a significant increase (18%) in high density lipoprotein phospholipids. This increased activity was accompanied by approximately 100% increase in phospholipid transfer protein mRNA in lung. After lipopolysaccharide injection, plasma phospholipid transfer protein activity was decreased by approximately 66%. This decrease in activity was associated with a similar decrease in phospholipid transfer protein mRNA in lung, adipose tissue, and liver. The decrease in plasma phospholipid transfer protein activity was also associated with a significant increase (17%) in high density lipoprotein phospholipid concentration. The opposite changes in phospholipids levels with lipopolysaccharide treatment and dietary cholesterol despite similarly increased high density lipoprotein phospholipids levels indicate that high density lipoprotein phospholipids levels are likely determined both by phospholipid transfer protein levels and by gradients of phospholipids concentration between high density lipoprotein and other phospholipids sources.

Amino Acid Sequence↗
PubMed1983

Studies on the turnover of endogenous choline-containing phospholipids of cultured neuroblastoma cells.

Previous studies on neuroblastoma cells in culture showed that the presence of partially purified rat liver phospholipid-transfer protein had a marked differential effect on the uptake and apparent subcellular distribution of radioactively labeled sphingomyelin and phosphatidylcholine (PC) added to the medium as mixed phospholipid (PC/sphingomyelin) liposomes. To determine the effect of phospholipid-transfer protein and exogenous phospholipids on the turnover and subcellular distribution of endogenous phospholipids, neuroblastoma cells were preincubated for 48 h in the presence of [methyl-3H]choline and washed. Aliquots of prelabeled cells were reincubated immediately in medium containing phospholipid-transfer protein mixed phospholipid liposomes, cytochalasin B and 2-deoxyglucose for 45 min at 37 degrees C; additional aliquots were chased first for 2 or 18 h with unlabeled choline before reincubation. The extent of labeled phospholipid degradation and accumulation in the medium, and the subcellular distribution of cell-associated labeled choline-containing phospholipids were determined. During incubation with phospholipid-transfer protein and mixed phospholipid liposomes, 25-35% of the cell-associated radioactive label from prelabeled cells, chased or unchased, was lost to the medium in 45 min. Over 50% of the label appearing in the medium was in water-soluble phospholipid degradation products. The loss of cell-associated label into the medium from unchased cells was stimulated significantly by phospholipid-transfer protein; however, prelabeled cells which had been chased for 18 h with unlabeled choline were unaffected by the presence of transfer protein. Endogenously synthesized radioactively labeled PC and sphingomyelin were distributed throughout all subcellular membranes, but least of all in the crude mitochondrial membrane fraction. Analysis of the subcellular distribution of cell-associated label remaining in chased or unchased cells after 45 min incubation with PC/sphingomyelin liposomes showed proportionate losses from all membrane fractions, except the crude mitochondrial fraction, which showed relative retention of labeled phospholipid. Phospholipid-transfer protein had no effect. The results are in distinct contrast to observations on the turnover, metabolism and subcellular distribution of labeled exogenous phospholipids under the same conditions, indicating that exogenous phospholipids do not intermix freely with any quantitatively major pool of endogenous phospholipid.

Animals↗
PubMed1975

Studies on cytochrome oxidase. Interactions of the cytochrome oxidase protein with phospholipids and cytochrome c.

1. By the application of the principle of the sequential fragmentation of the respiratory chain, a simple-method has been developed for the isolation of phospholipid-depleted and phospholipid-rich cytochrome oxidase preparations. 2. The phospholip-rich oxidase contains about 20% lipid, including mainly phosphatidylethanolamine, phosphatidylcholine, and cardiolipin. Its enzymic activity is not stimulated by an external lipid such as asolectin. 3. The phospholipid-depleted oxidase contains less than 0.1% lipid. It is enzymically inactive in catalyzing the oxidation of reduced cytochrome c by molecular oxygen. This activity can be fully restored by asolectin; and partially restored (approximately 75%) by purified phospholipids individually or in combination. The activity can be partially restored also by phospholipid mixtures isolated from mitochondria, from the oxidase itself, and from related preparations. Among the detergents tested only Emasol-1130 and Tween 80 show some stimulatory activity. 4. The phospholipid-depleted oxidase binds with cytochrome c evidently by "protein-protein" interactions as does the phospholipid-rich or the phospholipid-replenished oxidase to form a complex with the ratio of cytochrome c to heme a of unity. The complex prepared from phospholipid-depleted cytochrome oxidase exhibits a characteristic Soret absorption maximum at 415 nm in the difference spectrum of the carbon monoxide-reacted reduced form minus the reduced form. This 415-nm maximum is abolished by the replenishment of the complex with a phospholipid or by the dissociation of the complex in cholate or in a medium of high ionic strength. When ascorbate is used as an electron donor, the complex prepared from phospholipid-depleted cytochrome oxidase does not cause the reduction of cytochrome a3 which is in dramatic contrast to the complex from the phospholipid-rich or the phospholipid-replenished oxidase. However, dithionite reduces cytochrome a3 in all of the preparations of the cytochrome c-cytochrome oxidase complex. These facts suggest that the action of phospholipid on the electron transfer in cytochrome oxidase may be at the step between cytochromes a and a3. This conclusion is substantiated by preliminary kinetic results that the electron transfer from cytochrome a to a3 is much slower in the phospholipid-depleted than in phospholipid-rich or phospholipid-replenished oxidase. On the basis of the cytochrome c content, the enzymic activity has been found to be about 10 times higher in the system with the complex (in the presence of the replenishedhe external medium unless energy is provided, and that

Animals↗
PubMed1991

Lipid asymmetry in rabbit small intestinal brush border membrane as probed by an intrinsic phospholipid exchange protein.

All classes of phospholipids present in brush border membrane are exchanged in a 1:1 ratio for egg phosphatidylcholine when brush border membrane vesicles from rabbit small intestine are incubated with small unilamellar vesicles of egg phosphatidylcholine. The exchange reaction exhibits biphasic kinetics similar to those of the hydrolysis of brush border membrane phospholipids by phospholipase A2 and sphingomyelinase C. In both reactions there is an initial fast phase followed by a markedly slower one. The phospholipid exchange appears to be catalyzed by intrinsic brush border membrane protein(s), while the digestion by phospholipases is mediated by externally added enzymes. From a comparison of the kinetics of phospholipid exchange and phospholipid hydrolysis, the following conclusions can be drawn: Both sets of experiments indicate the presence of two phospholipid pools differing in the rate of phospholipid exchange and hydrolysis. Except for sphingomyelin, the size of the two phospholipid pools derived from phospholipid exchange is in good agreement with that derived from phospholipid hydrolysis. This is the main finding of this work, and on the basis of this result the two lipid pools are tentatively assigned to phospholipid molecules located on the outer and inner layer of the brush border membrane. The slow rate of phospholipid exchange reflects the rate of transverse or flip-flop movement of phospholipids. The half-time of this motion is approximately 8 h for isoelectric (neutral) phospholipids such as phosphatidylethanolamine and approximately 80 h for negatively charged phosphatidylserine and phosphatidylinositol. Isoelectric phospholipids (phosphatidylcholine, phosphatidylethanolamine) are preferentially located on the inner (cytoplasmic) side (to about 70%) while the negatively charged phospholipids are more evenly distributed: 55-60% are located on the inner side.

Animals↗
PubMed1998

Analysis of membrane phospholipid peroxidation by isocratic high-performance liquid chromatography with ultraviolet detection.

A new high-performance liquid chromatography (HPLC) for separation of phospholipid classes with ultraviolet (UV) detection at 210 nm was applied to study of peroxidation of the human erythrocyte membranes induced by soybean lipoxygenase. Phospholipid hydroperoxide production of each phospholipid was monitored at the same time by UV at 234 nm. Each phospholipid class was collected directly from the HPLC of phospholipids and was subjected to fatty acid analysis. All phospholipid classes except sphingomyelin were significantly decreased by lipoxygenase. Production of each phospholipid hydroperoxide was according to the decrease of its corresponding phospholipid class. Polyunsaturated fatty acids of each phospholipid were preferentially decreased with lipoxygenase, and degrees of the changes of the phospholipid classes corresponded to the amount of polyunsaturated fatty acids of each phospholipid. alpha-Tocopherol suppressed the decrease of the membrane phospholipids by peroxidation and suppressed also the production of malondialdehyde. However, production of phospholipid hydroperoxides appeared to be not suppressed by alpha-tocopherol. The present HPLC method proved to be sensitive to peroxidation of phospholipids and could detect the changes of each phospholipid class including phosphatidylserine and phosphatidylinositol at a single chromatographic elution. Production of hydroperoxide of each phospholipid could be detected simultaneously.

Adult↗
PubMed1993

Calcium-dependent annexin V binding to phospholipids: stoichiometry, specificity, and the role of negative charge.

Annexin V is a Ca(2+)-dependent, phospholipid-binding protein that may have one or more membrane-related functions. The binding of annexin V to phospholipids in a detergent micelle matrix was studied to attempt to determine directly the stoichiometry of specific phospholipid-binding sites and the importance of negative charge. When annexin V binds to phospholipids, a large increase (severalfold) of the emission intensity of tryptophan 187 is observed. This intensity change was used to monitor the binding to phosphatidylcholine (PC) or phosphatidylserine (PS) at varying ratios with the detergent, octaethylene glycol monododecyl ether (C12E8). No binding to PC alone in these micelles could be observed, while approximately 10 PS molecules per micelle were required to observe binding. However, inclusion of negatively charged amphiphiles in the micelles, such as oleic acid or dodecyl sulfate, allowed the observation of binding to PC and decreased the number of phospholipids per micelle necessary for binding to both PS and PC. By including increasing proportions of dodecyl sulfate in the C12E8 micelles, a minimum average number of PS or PC per micelle of approximately 3-4 was required for complete binding. Labeling with photoreactive phospholipids under similar conditions led to an average of approximately 4-5 phospholipids covalently bound per annexin V monomer. Since annexin V has four similar domains, it is reasonable to suggest that one phospholipid binding site is associated with each domain, although as few as three functional domains may be sufficient for binding. Efficient binding required certain structural features of the phospholipid, including a phosphate group, an sn-2 acyl chain, and at least a few carbons on the sn-2 chain. Phospholipid headgroups were almost irrelevant, except for important surface charge effects on the interfacial ionic double layer. A negative surface charge on the micellar aggregate nonspecifically increases the Ca2+ concentration near the micelle surface and may also directly enhance the affinity of annexin V for phospholipids, as shown by the decreased two-dimensional phospholipid concentration necessary for binding. The ability to bind to zwitterionic phospholipids in the presence of a nonspecific negative surface charge may be relevant to the extracellular functions of this protein. Relatively weak individual phospholipid-binding sites that easily exchange were observed, suggesting rapid exchange of phospholipids between the sites on membrane-bound annexin V. These data suggest a working hypothesis that includes approximately four binding sites specific for phospholipid phosphate groups and sn-2 acyl chains.(ABSTRACT TRUNCATED AT 400 WORDS)

Annexin A5↗
PubMed1999

Dietary phospholipid-dependent reductions in gene expression and activity of liver enzymes in fatty acid synthesis in fasted-refed rats.

The effects of dietary soybean phospholipid, its hydrogenation product and safflower phospholipid on gene expression and the activity of hepatic enzymes in fatty acid biosynthesis were examined in fasted-refed rats. Phospholipid composition of soybean phospholipid and its hydrogenation product were the same, but the hydrogenation product contained negligible amounts of unsaturated fatty acids. Among phospholipid classes, lysophosphatidylcholine and phosphatidylinositol proportions were slightly higher in safflower phospholipid than in soybean phospholipid or its hydrogenation product. Rats were fasted for 2 d and refed a fat-free diet or a diet containing 4% fatty acids either as soybean oil or various phospholipid preparations for 3 d. Compared to the fat-free diet, the soybean oil diet only slightly decreased specific, but not total hepatic fatty acid synthetase and malic enzyme activity, and it was totally ineffective in modulating glucose 6-phosphate dehydrogenase and pyruvate kinase activity under our experimental conditions. The diets containing phospholipids, however, markedly decreased the activity of these enzymes. The extent of reduction was somewhat attenuated with hydrogenated soybean phospholipid as compared with soybean and safflower phospholipids. Dot and Northern blot hybridization using specific cDNA probes showed that, compared to a fat-free diet, diets containing phospholipids profoundly decreased the hepatic mRNA levels of enzymes in fatty acid synthesis. Soybean oil, however, only marginally affected these parameters. Hepatic mRNA levels for enzymes correlated well with enzyme activity. Dietary phospholipids therefore appear to have decreased enzyme activity in fatty acid synthesis primarily by suppressing the mRNA levels of these enzymes. Compared to soybean oil, hydrogenated soybean phospholipid is still effective in decreasing the activity and mRNA level of enzymes in fatty acid synthesis. Therefore, it is difficult to ascribe the potent physiological activity of phospholipid in reducing fatty acid synthesis entirely to polyunsaturated fatty acid moiety.

Animals↗