Malaria species and Southeast Asian ovalocytosis defined by a 27-bp deletion in the erythrocyte band 3 gene

To evaluate the resistance of SAO against species specific malaria infection, relationships between parasite species and the 27-bp deletion in the band 3 gene were studied in malaria endemic Sumba Island, eastern Indonesia. Thick blood films were prepared from patients with malaria symptoms (n=129) and healthy controls (n=231). Species of Plasmodium was identified by microscopic observation. The 27-bp deletion was screened by the PCR method. Among 231 healthy controls, 29 (12.6%) had the 27-bp deletion, whereas 14 (10.9%) among 129 patients confirmed with malaria infection harbored the 27-bp deletion. No significant difference was observed in the prevalence of the 27-bp deletion between controls and patients (p>0.8). There was no significant difference in the frequency of the 27-bp deletion between P. vivax and P. falciparum infected subjects at 5% level by Fisher's exact test. The present result showing no correlation between the presence of the 27-bp deletion and infected parasite species is consistent with the post-invasion resistance hypothesis that may involve not a single malaria species.     

Prevention of cerebral malaria in children in Papua New Guinea by southeast Asian ovalocytosis band 3.

Southeast Asian ovalocytosis (SAO) occurs at high frequency in malarious regions of the western Pacific and may afford a survival advantage against malaria. It is caused by a deletion of the erythrocyte membrane band 3 gene and the band 3 protein mediates the cytoadherence of parasitized erythrocytes in vitro. The SAO band 3 variant may prevent cerebral malaria but it exacerbates malaria anemia and may also increase acidosis, a major determinant of mortality in malaria. We undertook a case-control study of children admitted to hospital in a malarious region of Papua New Guinea. The SAO band 3, detected by the polymerase chain reaction, was present in 0 of 68 children with cerebral malaria compared with six (8.8%) of 68 matched community controls (odds ratio = 0, 95% confidence interval = 0-0.85). Median hemoglobin levels were 1.2 g/dl lower in malaria cases with SAO than in controls (P = 0.035) but acidosis was not affected. The remarkable protection that SAO band 3 affords against cerebral malaria may offer a valuable approach to a better understanding of the mechanisms of adherence of parasitized erythrocytes to vascular endothelium, and thus of the pathogenesis of cerebral malaria.     

Oxidation-induced changes in microrheologic properties of the red blood cell membrane

It has been hypothesized that some of the irreversible microrheologic abnormalities of sickle red blood cell (RBC) membranes could result from autoxidative perturbation. To model this possibility, we used micromechanical manipulation to examine the static extensional rigidity and inelastic or plastic behavior of normal RBCs exposed to phenazine methosulfate (PMS), an agent that generates superoxide from within the cell. In response to this stress, RBC membranes became stiff as evidenced by increasing extensional rigidity. At 50 mumol/L PMS they were as stiff as the membranes of most dense, dehydrated sickle RBCs; and at 25 mumols/L PMS the membranes were similar to somewhat less dense sickle RBCs. When examined for inelastic behavior, RBCs exposed to PMS even at 10 mumols/L showed hysteresis in loading and unloading phases of the curve relating aspiration length to suction pressure, and they developed membrane bumps that persisted after RBC release from the pipette. Examination of single cells in both isotonic and hypotonic buffers showed that the effect of PMS on RBC microheology is not mediated by cellular dehydration. Independent confirmation of the membrane stiffening effect of PMS was obtained by ektacytometric analysis of resealed RBC ghosts, with sickle-like increases in membrane rigidity observed between 50 and 100 mumol/L PMS. The rigidity of these ghosts was partially ameliorated by exposure to a thiol reductant. In terms of biochemical abnormalities, treated RBCs became significantly different from control RBCs at 25 mumol/L PMS, at which point they just began to enter the sickle range for amounts of membrane thiol oxidation and membrane-associated heme. The sickle average was achieved at 50 mumol/L PMS (for thiol oxidation) to 100 mumol/L PMS (for membrane heme). Thus, micromolar concentrations of PMS induce abnormalities of membrane microrheology that closely mimic those of unmanipulated sickle RBCs while reproducing similar degrees of oxidative biochemical change. We conclude that membrane protein oxidation could explain existence of an irreversible component to the abnormal rheology of the sickle membrane.     

The instability of the membrane skeleton in thalassemic red blood cells

The thalassemias are a heterogeneous group of disorders characterized by accumulation either of unmatched alpha or beta globin chains. These in turn cause the intramedullary and peripheral hemolysis that leads to varying anemia. A partial explanation for the hemolysis came our of our studies on material properties that showed that beta-thalassemia (beta- thal) intermedia ghosts were very rigid but unstable. A clue to this instability came from the observation that the spectrin/band 3 ratio was low in red blood cells (RBCs) of splenectomized beta-thal intermedia patients. The possible explanations for the apparent decrease in spectrin content included deficient or defective spectrin synthesis in thalassemic erythroid precursors or globin chain-induced membrane changes that lead to spectrin dissociation from the membrane during ghost preparation. To explore the latter alternative, samples from different thalassemic variants were obtained, ie, beta-thal intermedia, HbE/beta-thal, HbH (alpha-thal-1/alpha-thal-2), HbH/Constant Spring (CS), and homozygous HbCS/CS. We searched for the presence of spectrin in the first lysate of the standard ghost preparation. Normal individuals and patients with autoimmune hemolytic anemia, sickle cell anemia, and anemia due to chemotherapy served as controls. Using gradient sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, no spectrin was detected in identical aliquots of the supernatants of normals and these control samples. Varying amounts of spectrin were detected in the first lysate supernatants of almost all thalassemic patients. The identification of spectrin was confirmed by Western blotting using an affinity-purified, monospecific, rabbit polyclonal antispectrin antibody. Relative amounts of spectrin detected were as follows in decreasing order: splenectomized beta-thal intermedia including HbE/beta-thal; HbCS/CS; nonsplenectomized beta-thal intermedia, HbH/CS; and, lastly, HbH. These findings were generally confirmed when we used an enzyme-linked immunosorbent assay technique to measure spectrin in the first lysate. Subsequent analyses showed that small amounts of actin and band 4.1 also appeared in lysates of thalassemic RBCs. Therefore, the three major membrane skeletal proteins are, to a varying degree, unstably attached in severe thalassemia. From these studies we could postulate that membrane association of abnormal or partially oxidized alpha- globin chains has a more deleterious effect on the membrane skeleton than do beta-globin chains.     

Mutations in the murine erythroid alpha-spectrin gene alter spectrin mRNA and protein levels and spectrin incorporation into the red blood cell membrane skeleton

Tetramers of alpha- and beta-spectrin heterodimers, linked by intermediary proteins to transmembrane proteins, stabilize the red blood cell cytoskeleton. Deficiencies of either alpha- or beta-spectrin can result in severe hereditary spherocytosis (HS) or hereditary elliptocytosis (HE) in mice and humans. Four mouse mutations, sph, sph(Dem), sph(2BC), and sph(J), affect the erythroid alpha-spectrin gene, Spna1, on chromosome 1 and cause severe HS and HE. Here we describe the molecular alterations in alpha-spectrin and their consequences in sph(2BC)/sph(2BC) and sph(J)/sph(J) erythrocytes. A splicing mutation, sph(2BC) initiates the skipping of exon 41 and premature protein termination before the site required for dimerization of alpha-spectrin with beta-spectrin. A nonsense mutation in exon 52, sph(J) eliminates the COOH-terminal 13 amino acids. Both defects result in instability of the red cell membrane and loss of membrane surface area. In sph(2BC)/sph(2BC), barely perceptible levels of messenger RNA and consequent decreased synthesis of alpha-spectrin protein are primarily responsible for the resultant hemolysis. By contrast, sph(J)/sph(J) mice synthesize the truncated alpha-spectrin in which the 13-terminal amino acids are deleted at higher levels than normal, but they cannot retain this mutant protein in the cytoskeleton. The sph(J) deletion is near the 4.1/actin-binding region at the junctional complex providing new evidence that this 13-amino acid segment at the COOH-terminus of alpha-spectrin is crucial to the stability of the junctional complex.     

Possible role of flexible red blood cell membrane nanodomains in the growth and stability of membrane nanotubes

Tubular budding of the erythrocyte membrane may be induced by exogenously added substances. It is shown that tubular budding may be explained by self-assembly of anisotropic membrane nanodomains into larger domains forming nanotubular membrane protrusions. In contrast to some previously reported theories, no direct external mechanical force is needed to explain the observed tubular budding of the bilayer membrane. The mechanism that explains tubular budding may also be responsible for stabilization of the thin tubes that connect cells or cell organelles and which might be important for the transport of matter and information in cellular systems. It is shown that small carrier vesicles (gondolas), transporting enclosed material or the molecules composing their membrane, may travel over long distances along the nanotubes connecting two cells.     

Globin-chain specificity of oxidation-induced changes in red blood cell membrane properties.

We have previously shown that excess unpaired alpha- and beta-globin chains in severe alpha- and beta-thalassemia interacting with the membrane skeleton induce different changes in membrane properties of red blood cells (RBCs) in these two phenotypes. We suggest that these differences in membrane material behavior may reflect the specificity of the membrane damage induced by alpha- and beta-globin chains. To further explore this hypothesis, we sought in vitro models that induce similar membrane alterations in normal RBCs. We found that treatment of normal RBCs with phenylhydrazine produced rigid and mechanically unstable membranes in conjunction with selective association of oxidized alpha-globin chains with the membrane skeleton, features characteristic of RBCs in severe beta-thalassemia. Methylhydrazine, in contrast, induced selective association of oxidized beta-globin chains with the membrane skeleton and produced rigid but hyperstable membranes, features that mimicked those of RBCs in severe alpha-thalassemia. These findings suggest that consequences of oxidation induced by globin chains are quite specific in that those agents that cause alpha-globin chain accumulation at the membrane produce rigid but mechanically unstable membranes, whereas membrane accumulation of beta-globin chains results in rigid but mechanically stable membranes. These in vitro experiments lend further support to the hypothesis that membrane-associated alpha- and beta-chains induce oxidative damage to highly specific different skeletal components and that the specificity of this skeletal damage accounts for the differences in material membrane properties of these oxidatively attacked RBCs and perhaps of alpha- and beta-thalassemic RBCs as well.     

Oxidation of membrane proteins and functional activity of band 3 in human red cell senescence

The state of oxidation of membrane proteins was analyzed in red cell subpopulations of different age by quantifying the oxidation of methionine to its sulfoxide and by determining the amount of thiol groups in ghost membrane preparations and the reactivity of thiols of individual membrane proteins in intact cells. The results obtained show that oxidation of methionine occurs early during red cell life in the circulation, and can be detected in middle-aged and senescent cells. Thiol content of ghost membranes is kept constant in all the red cell subpopulations analyzed, but reactivity of thiol groups to the thiol reagent N-(7-dimethyl-amino-4-methyl-coumarinyl) maleimide (DACM) in intact cells decreased 30% in alpha-spectrin, band 3 (B3), 4.1 and 4.2 proteins, probably as a consequence of conformational changes of these molecules. Since the role played by band 3 in the exposure of senescence antigen has been described by many authors, the functional activity of the anion transporter has been analyzed by measuring the 4-4'-diisothiocyano-stilbene-2-2-'-disulfonate (DIDS) binding capacity in different red cell subpopulations. The results obtained are in agreement with the possibility that during senescence band 3 undergoes conformational changes involving the anion channel subsite being more exposed to the extracellular space and responsible for binding of DIDS.     

Effects of Poloxamer 188 on red blood cell membrane properties in sickle cell anaemia

Vaso‐occlusive crisis (VOC) is the main acute complication in sickle cell anaemia (SS) and several clinical trials are investigating different drugs to improve the clinical severity of SS patients. A phase III study is currently exploring the profit of Velopoloxamer in SS during VOCs. We analysed, in‐vitro, the effect of poloxamer (P188) on red blood cell (RBC) properties by investigating haemorheology, mechanical and adhesion functions using ektacytometry, microfluidics and dynamic adhesion approaches, respectively. We show that poloxamer significantly reduces blood viscosity, RBC aggregation and adhesion to endothelial cells, supporting the beneficial use of this molecule in SS therapy.     

Association state of human red blood cell band 3 and its interaction with ankyrin

We have studied the association state of band 3, the anion channel and predominant transmembrane protein of the human red blood cell, and the anomalous stoichiometry and dynamics of its interaction with ankyrin, which acts as a link to the spectrin of the membrane skeletal network. Band 3 exists in benign nonionic detergent solutions as a dimer. Tetramer is formed irreversibly in the course of manipulations, particularly in ion-exchange chromatography. The dimer in solution binds ankyrin without self-associating. In ankyrin-free inside-out membrane vesicles and when incorporated into phosphatidylcholine liposomes, only some 10% to 15% of band 3 chains bind ankyrin at saturation. Moreover, in liposomes this was independent of protein:lipid ratio between 1:2 and 1:40. The bound fraction of band 3 remains with the detergent-extracted membrane cytoskeleton, but is released if the ankyrin has been cleaved with chymotrypsin before detergent treatment; thus, the attachment to the membrane cytoskeleton is entirely through ankyrin and not through other constituents such as protein 4.1. The ratio of band 3 to ankyrin in this complex implies that it consists of two chains of band 3 and one chain of ankyrin, at least after detergent extraction. The bound and free populations of band 3 exchange freely in the membrane. In the artificial liposome membrane binding of ankyrin to band 3 dimers cause association of the band 3 into higher aggregates, as seen in freeze-fracture electron microscopy. Successive manipulations of the red blood cell membrane, which are involved in the preparation of ghosts, of inside-out vesicles, and of inside-out vesicles stripped of peripheral proteins are accompanied by progressive aggregation of intramembrane particles, as judged by freeze-fracture electron microscopy. Thus the intramembrane particles are evidently stabilized in the intact cell by the peripheral protein network and the cytosolic milieu. Aggregation may be expected to limit the number of functional ankyrin binding sites. However, although extraneous ankyrin binds to the unoccupied binding site on the spectrin tetramers in intact ghost membranes, little or no ankyrin can bind to the unoccupied band 3 dimers in situ, perhaps by reason of occlusion of binding sites by the membrane skeletal network.     

Molecular architecture and dynamics of the plasma membrane lipid bilayer: The red blood cell as a model

The structural backbone of the erythrocyte membrane, as well as that of any other plasma membrane, is provided by a lipid bilayer which is composed of more than 100 molecular species. The individual lipid classes are distributed over both halves of the bilayer in a highly asymmetric fashion: all glycolipids are exclusively confined to the outer membrane leaflet where we also find the majority of the two choline-containing phospholipids, sphingomyelin and phosphatidylcholine. The two amino-phospholipids are predominantly (phosphatidylethanolamine) or even exclusively (phosphatidylserine) localized in the cytoplasmic half of the bilayer. Glycolipids and sphingomyelin are not subject to transbilayer movements, a property that (under normal conditions) is shared by phosphatidylserine. Phosphatidylcholine exhibits a relatively slow transbilayer movement, revealing half-time values from 3 to 27 h, whereas phosphatidylethanolamine is subject to an ATP-dependent flippase-catalyzed inward movement with a half-time of approximately 30 min. Probably much faster than that of any other lipid, is the transbilayer movement of cholesterol, revealing a half-time value in the order of seconds.Das strukturelle Rückgrat der Erythrozytenmembran wie auch jeder anderen Membran wird durch eine Lipid-Doppelschicht gebildet, die aus mehr als 100 verschiedenen Molekülarten zusammengesetzt ist. Die einzelnen Lipidklassen sind über beide Hälften der Doppelschicht hochgradig asymmetrisch verteilt. Glykolipide befinden sich ausschließlich in der äußeren Schicht der Membran, in der auch die meisten Moleküle der beiden cholinhaltigen Phospholipide (Sphingomyelin und Phosphatidylcholin) anzutreffen sind. Die beiden Amino-Phospholipide sind vorwiegend (Phosphatidylethanolamin) oder sogar ausschließlich (Phosphatidylserin) in der zytoplasmatischen Hälfte der Doppelschicht gelegen. Glykolipide und Sphingomyelin sind nicht an den Bewegungen durch die Doppelschicht beteiligt; diese Eigenschaft hat (unter normalen Bedingungen) auch Phosphatidylserin. Phosphatidylcholin zeigt eine relativ langsame Bewegung durch die Doppelschicht mit Halbwertzeiten von 3 bis 27 Stunden; Phosphatidylethanolamin hingegen unterliegt einer durch eine ATP-abhängige, flippase katalysierten Bewegung mit einer Halbwertzeit von etwa 30 Minuten. Der Transport von Cholesterin durch die Doppelschicht vollzieht sich wahrscheinlich viel schneller als der irgendeines anderen Lipids, die Halbwertzeit liegt dabei im Bereich von Sekunden.     

The interactome of the N-terminus of band 3 regulates red blood cell metabolism and storage quality

Band 3 (anion exchanger 1; AE1) is the most abundant membrane protein in red blood cells, which in turn are the most abundant cells in the human body. A compelling model posits that, at high oxygen saturation, the N-terminal cytosolic domain of AE1 binds to and inhibits glycolytic enzymes, thus diverting metabolic fluxes to the pentose phosphate pathway to generate reducing equivalents. Dysfunction of this mechanism occurs during red blood cell aging or storage under blood bank conditions, suggesting a role for AE1 in the regulation of the quality of stored blood and efficacy of transfusion, a life-saving intervention for millions of recipients worldwide. Here we leveraged two murine models carrying genetic ablations of AE1 to provide mechanistic evidence of the role of this protein in the regulation of erythrocyte metabolism and storage quality. Metabolic observations in mice recapitulated those in a human subject lacking expression of AE11-11 (band 3 Neapolis), while common polymorphisms in the region coding for AE11-56 correlate with increased susceptibility to osmotic hemolysis in healthy blood donors. Through thermal proteome profiling and crosslinking proteomics, we provide a map of the red blood cell interactome, with a focus on AE11-56 and validate recombinant AE1 interactions with glyceraldehyde 3-phosphate dehydrogenase. As a proof-of-principle and to provide further mechanistic evidence of the role of AE1 in the regulation of redox homeo stasis of stored red blood cells, we show that incubation with a cell-penetrating AE11-56 peptide can rescue the metabolic defect in glutathione recycling and boost post-transfusion recovery of stored red blood cells from healthy human donors and genetically ablated mice.     

Aging and red blood cell membrane: a study of centenarians

Successful aging, characterized by little or no loss in physiological functions, should be the usual aging process in centenarians. It is known that well-preserved physiological functions depend on the proper functioning of cell systems. In this article we focus on cell membrane integrity and study the red blood cell membrane to evaluate the effect of physiological aging in centenarians. Fifteen healthy, self-sufficient centenarians, mean age 103 years, were examined by assessing hemocytometric values and some relevant characteristics of the erythrocyte membrane, i.e., the cholesterol/phospholipid molar ratio, the distribution of phospholipid classes and their fatty acid composition, the integral and skeletal protein profiles. The centenarians showed a significant decrease in the red blood cell count (p < 0.0002), hemoglobin (p < 0.0002), and hematocrit (p < 0.0005). The red blood cell membrane showed a significantly increased cholesterol/phospholipid molar ratio (p < 0.01), with a concomitant increase in polyunsaturated fatty acids in phosphatidylcholine (p < 0.001) and, to a lesser extent, in phosphatidylethanolamine. The electrophoretic pattern of membrane proteins was qualitatively normal compared to controls but the densitometric analysis showed a significant increase in the integral protein band 4.2 (p < 0.05) and in the skeletal protein actin (p < 0.001). Extreme longevity seems to be associated with a substantial integrity of the erythrocyte membrane. Moreover, the evident increase in polyunsaturated fatty acids and in actin are likely to improve the membrane fluidity and to strengthen the membrane structure.     

Erythrocyte membrane proteins reactive with IgG (warm-reacting) anti- red blood cell autoantibodies: II. Antibodies coprecipitating band 3 and glycophorin A

In our initial immunochemical study of the red blood cell (RBC) membrane proteins targeted in 20 cases of warm-antibody autoimmune hemolytic anemia (AHA), RBC eluates of 6 patients mediated immunoprecipitation (IP) of both band 3 and glycophorin A (GPA). This dual IP pattern had previously been observed with murine monoclonal antibodies (MoAbs) against the high frequency blood group antigen, Wrb (Wright), suggesting that the Wrb epitope may depend on a band 3-GPA interaction. Earlier, anti-Wrb had been identified serologically as a prominent non-Rh specificity of AHA autoantibodies. In the present study, 6 autoantibody eluates immunoprecipitating band 3 and GPA from common Wr(b+) RBCs were retested, in parallel with murine anti-Wrb MoAbs, against very rare Wr(a+b-)En(a+)RBCs. One patient's autoantibodies were unreactive with the Wr(b-) RBCs by either IP or indirect antiglobulin test (IAT) and were judged to have "pure" anti- Wrb specificity. Two other patients' autoantibodies displayed both IP and serologic evidence for anti-Wrb as a major component in combination with one or more additional specificities. However, among 3 other patients whose autoantibodies coprecipitated band 3 and GPA, there was no reduction in IP or IAT reactivity with Wr(b-) RBCs in 2 and only slight reduction in the third. We conclude (1) that human anti-Wrb autoantibodies, like their murine monoclonal counterparts, coprecipitate band 3 and GPA from human RBCs; but (2) that not all antibodies with this IP behavior have anti-Wrb serologic specificity, as defined by this donor's Wr(b-) RBCs. The possibility of an additional (non-Wrb) RBC epitope dependent on a band 3-GPA interaction is raised.