scholarly journals Phosphoinositide metabolism and the morphology of human erythrocytes.

1984 ◽  
Vol 98 (6) ◽  
pp. 1992-1998 ◽  
Author(s):  
J E Ferrell ◽  
W H Huestis
Keyword(s):  
Phosphatidic Acid ◽  
Shape Change ◽  
Human Erythrocytes ◽  
Phosphoinositide Metabolism ◽  
Nutrient Supplementation ◽  
Related Process

ATP-depleted human erythrocytes lose their smooth discoid shape and adopt a spiny, crenated form. This shape change coincides with the conversion of phosphatidylinositol-4,5-bisphosphate to phosphatidylinositol and phosphatidic acid to diacylglycerol. Both crenation and lipid dephosphorylation are accelerated by iodoacetamide, and both are reversed by nutrient supplementation. The observed changes in lipid populations should shrink the membrane inner monolayer by 0.6%, consistent with estimates of bilayer imbalance in crenated cells. These observations suggest that metabolic crenation arises from a loss of inner monolayer area secondary to the degradation of phosphatidylinositol-4,5-bisphosphate and phosphatidic acid. A related process, crenation after Ca2+ loading, appears to arise from a loss inositides by a different pathway.

Changes In Triphosphatidylinositol Metabolism During PGE1- Induced Shape Change Of Washed Rabbit Platelets

1981 ◽  
Author(s):  
J D Vickers ◽  
R L Kinlough-Rathbone ◽  
J F Mustard
Keyword(s):  
Phosphatidic Acid ◽  
Shape Change ◽  
Specific Radioactivity ◽  
Inositol Phospholipids ◽  
Rabbit Platelets ◽  
Turn Over ◽  
Camp Levels ◽  
Camp Formation ◽  
Platelet Shape ◽  
Stimulation Of

Since the inositol phospholipids are present in small amounts in platelets and turn over rapidly during platelet shape change, aggregation and release, they are thought to have a functional rather than structural role in platelets. We have previously reported that within 10 sec of stimulation of prelabeled, washed rabbit platelets with ADP, the amount of triphosphatidylinositol (TPI) is significantly reduced while the specific radioactivity of its [32p]phosphate is increased. One explanation of this result is that ADP- stimulation may divert ATP required for phosphorylation of diphosphatidylinositol (DPI) to TPI, leading to a decrease in the amount of TPI. PGE1 (10 μM) causes conversion of ATP to cAMP and induces a transient platelet shape change. The shape change may be due to the reduction in ATP with a concomitant fall in TPI. We have therefore studied whether PGE1-stimulation of washed rabbit platelets prelabeled with [32P] causes a change in TPI. Within 10 sec the amount of TPI in PGE1-treated platelets was reduced from 2.22 nmoles/ 109 platelets to 1.98 nmoles/109 platelets (p<0.05) although neither the [32P] labeling (51.1 × 103 dpm/109 platelets) nor specific radioactivity (24.1 × 103 dpm/nmole) were significantly changed. These results are compatible with the theory that diversion of ATP by PGE1-stimulation of cAMP formation from ATP, may reduce the amount of TPI. A similar effect was observed previously with ADP-stimulation. PGE1 caused no change in the [32p] labeling of phosphatidic acid (PA) (ADP caused a 290% increase) and caused only a small increase in its specific radioactivity (16% compared to 270% with ADP). If the rates of turnover of TPI and PA which are reflected in their specific radioactivities are Ca2+- dependent, Ca2+ sequestration due to increased cAMP levels induced by PGE1 would, after the initial effects, terminate these changes. The results further support the suggestion that reduction in the amount of TPI may be involved in platelet shape change and initiation of aggregation.

scholarly journals Quantitation of adenosine-5'-triphosphate used for phosphoinositide metabolism in human erythrocytes

Blood ◽  
1985 ◽  
Vol 66 (5) ◽  
pp. 1133-1137 ◽  
Author(s):  
GL Dale
Keyword(s):  
Steady State ◽  
Human Erythrocyte ◽  
Human Erythrocytes ◽  
Phosphoinositide Metabolism ◽  
Quasi Steady State ◽  
Futile Cycle ◽  
Independent Measure

Abstract The human erythrocyte actively phosphorylates and dephosphorylates phosphatidylinositol present in the membrane in an apparent “futile cycle.” Recent reports have proposed that this phosphorylation/dephosphorylation cycle is a significant consumer of adenosine-5′-triphosphate (ATP) in the erythrocyte. This study details two independent techniques for quantitating the ATP consumed by this phosphoinositide futile cycle. With the first technique a quasi-steady- state labeling of erythrocyte ATP with 32P-phosphate was obtained, and the rate of synthesis of 32P-phosphoinositides was then monitored. The second technique used a novel labeling strategy that allowed only ATP to be labeled with 32P; the transfer of 32P from ATP to phosphoinositides was then an independent measure of the ATP consumed for phosphoinositide synthesis. These two techniques documented that 0.5% to 1.0% of net ATP produced by the erythrocyte is used for phosphoinositide synthesis.

Procoagulant and prothrombotic activation of human erythrocytes by phosphatidic acid

2010 ◽  
Vol 299 (2) ◽  
pp. H347-H355 ◽  
Author(s):  
Ji-Yoon Noh ◽  
Kyung-Min Lim ◽  
Ok-Nam Bae ◽  
Seung-Min Chung ◽  
Sang-Wook Lee ◽  
...  
Keyword(s):  
Phosphatidic Acid ◽  
Thrombus Formation ◽  
Biological Activities ◽  
Human Erythrocytes ◽  
Erythrocyte Aggregation ◽  
Dependent Manner ◽  
Disease States ◽  
Thrombosis Model ◽  
Intracellular Ca

Increased phosphatidic acid (PA) and phospholipase D (PLD) activity are frequently observed in various disease states including cancers, diabetes, sepsis, and thrombosis. Previously, PA has been regarded as just a precursor for lysophosphatidic acid (LPA) and diacylglycerol (DAG). However, increasing evidence has suggested independent biological activities of PA itself. In the present study, we demonstrated that PA can enhance thrombogenic activities in human erythrocytes through phosphatidylserine (PS) exposure in a Ca2+-dependent manner. In freshly isolated human erythrocytes, treatment of PA or PLD induced PS exposure. PA-induced PS exposure was not attenuated by inhibitors of phospholipase A2or phosphatidate phosphatase, which converts PA to LPA or DAG. An intracellular Ca2+increase and the resultant activation of Ca2+-dependent PKC-α appeared to underlie the PA-induced PS exposure through the activation of scramblase. A marginal decrease in flippase activity was also noted, contributing further to the maintenance of exposed PS on the outer membrane. PA-treated erythrocytes showed strong thrombogenic activities, as demonstrated by increased thrombin generation, endothelial cell adhesion, and erythrocyte aggregation. Importantly, these procoagulant activations by PA were confirmed in a rat in vivo venous thrombosis model, where PA significantly enhanced thrombus formation. In conclusion, these results suggest that PA can induce thrombogenic activities in erythrocytes through PS exposure, which can increase thrombus formation and ultimately contribute to the development of cardiovascular diseases.

The influence of chlorpromazine on the potential-induced shape change of human erythrocyte

1991 ◽  
Vol 11 (4) ◽  
pp. 213-221 ◽  
Author(s):  
J. Hartmann ◽  
R. Glaser
Keyword(s):  
Red Blood Cells ◽  
Human Erythrocyte ◽  
Blood Cells ◽  
Characteristic Time ◽  
Time Course ◽  
Transmembrane Potential ◽  
Shape Change ◽  
Human Erythrocytes

The effect of chlorpromazine (CPZ) on the shape of human erythrocytes with different values of transmembrane potential (TMP) was investigated. The shape of red blood cells with negative values of the TMP remained unchanged after the formation of stomatocytes by chlorpromazine, while cells with positive TMP showed a characteristic time course of shape change during the incubation with CPZ. Experiments with vanadate show that this might be due to a difference in the activity of the phospholipid-translocase at different values of TMP.

The Effect of the Intracellular Calcium Chelator Quin-2 on the Platelet Phosphoinositide Metabolism, Protein Phosphorylation and Morphology

1987 ◽  
Vol 58 (03) ◽  
pp. 927-931 ◽  
Author(s):  
D de Chaffoy de Courcelles ◽  
P Roevens ◽  
F Verheyen ◽  
H Van Belle ◽  
F De Clerck
Keyword(s):  
Shape Change ◽  
Human Platelets ◽  
Phosphoinositide Metabolism ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Platelet Morphology ◽  
Receptor Signal ◽  
Microscopic Evaluation ◽  
32P Incorporation ◽  
Phosphatidylinositol 4

SummaryWhen human platelets prelabeled with [32P] orthophosphate were loaded with Quin-2, the 32P-incorporation in phosphatidic acid, phosphatidylinositol-4 phosphate and phosphatidylinositol-4,5 bisphosphate increased, that in phosphatidylinositol decreased. These effects occurred in a Quin-2-concentration- dependent manner. On stimulation of the serotonin-S2 receptor, signal transduction, measured as changes in labeling in phospholipids and phosphoproteins, was altered in the presence of the fluorophore. Microscopic evaluation illustrated that Quin-2 affected platelet morphology as well in resting as in stimulated platelets. A correlation between platelet shape change and myosin light chain phosphorylation was apparent.The data evidence that the Quin-2 that is widely used for fluorometric determination of intracellular Ca2+, affects the metabolism of inositol-containing phospholipids whose breakdown is a key event in Ca2i+-mobilization on excitatory platelet activation. These fluorophore-induced alterations might, besides the Ca2-chelating properties, play an important role in the Ca2+ dependent signalling processes in these cells.

Shape control in the human red cell

1986 ◽  
Vol 80 (1) ◽  
pp. 281-298
Author(s):  
L. Backman
Keyword(s):  
Phosphatidic Acid ◽  
Shape Control ◽  
Control Mechanism ◽  
Cytoskeletal Proteins ◽  
Phosphoinositide Metabolism ◽  
Red Cell ◽  
Spherical Form ◽  
Protein Dephosphorylation ◽  
Shape Changes ◽  
Bilayer Couple

When the human red cell consumes its ATP, the cell loses its discoid character in favour of a spiculated and eventually a spherical form. This discocyte-echinocyte transformation parallels both degradation of phosphatidylinositol 4,5-bisphosphate and phosphatidic acid but not dephosphorylation of cytoskeletal proteins. Dephosphorylation of both spectrin and band 3 lags behind metabolic crenation. Exogenous vanadate accelerates both shape changes and lipid dephosphorylation in a parallel manner during metabolic depletion. In contrast to its effect on lipids, vanadate reduces the rate of protein dephosphorylation. These observations strongly support a shape control mechanism in the red cell, based on phosphoinositide metabolism and compatible with a bilayer-couple model.

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