Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have recently shown that rosetting of Plasmodium falciparum (MC R+ line)-infected erythrocytes (parasitized red blood cells [PRBCs]) with uninfected erythrocytes (RBCs) is blocked by coating of the RBCs with anti-CD36 monoclonal antibodies (MoAbs; Handunnetti et al, Blood 80:2097, 1992). Adult RBCs have previously been considered negative for CD36. However, using fluorescence-activated cell sorter analysis with the anti-CD36 MoAbs 8A6, OKM5, and OKM8, which reverse rosetting, we consistently detect CD36 on the majority of normal adult RBCs. Absorption of the MoAb solutions with CD36-transfected Chinese hamster ovary (CHO-CD36) cells removed the reactivity against both CHO-CD36 cells and RBCs, whereas absorption with CHO cells had no effect. By comparison with staining for glycophorin A, LFA-3, and CR1, the level of expression of CD36 appeared to be low. Nevertheless, normal RBCs were capable of adhering to plastic coated with anti-CD36 MoAbs. RBCs from one African malaria patient were identified as deficient in CD36 and these RBCs did not rosette with the patient's own P falciparum PRBCs, even though these PRBCs were capable of rosetting with RBCs from a normal donor in a CD36-dependent manner. Therefore, the level of expression of CD36 on normal RBCs is sufficient to be important in cell adherence, and may have a biologic role in normal individuals as well as in the pathology of P falciparum malaria.
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PMID:Normal human erythrocytes express CD36, an adhesion molecule of monocytes, platelets, and endothelial cells. 138 21

The phospholipid and fatty acid compositions of the host infected erythrocyte plasma membrane (IEPM) have been determined for erythrocytes infected with the human malaria parasite Plasmodium falciparum. IEPM were prepared by selective lysis of the host erythrocyte (but not of the parasite membranes) with 0.1% saponin, followed by differential centrifugation. The purity of the IEPM was determined by measuring the membrane-specific enzyme markers acetylcholinesterase, glutamate dehydrogenase and lactate dehydrogenase, and by immunoelectron microscopy using monoclonal antibodies specific for human erythrocyte glycophorin A (4E7) and for a 195 kDa parasite membrane glycoprotein (Pf6 3B10.1). Both approaches demonstrated that the host erythrocyte plasma membrane preparation was free from contamination by parasite membranes. During intra-erythrocytic development of the parasite, the phospholipid composition of the erythrocyte membrane was strikingly altered. IEPM contained more phosphatidylcholine (38.7% versus 31.7%) and phosphatidylinositol (2.1% versus 0.8%) and less sphingomyelin (14.6% versus 28.0%) than normal uninfected erythrocytes. Similar alterations in phospholipid composition were determined for erythrocyte membranes of parasitized cells isolated by an alternative method utilizing polycationic polyacrylamide microbeads (Affigel 731). The total fatty acid compositions of the major phospholipids in IEPM were determined by g.l.c. The percentage of polyunsaturated fatty acids in normal erythrocyte phospholipids (39.4%) was much higher than in phospholipids from purified parasites (23.3%) or IEPM (24.0%). The unsaturation index of phospholipids in IEPM was considerably lower than in uninfected erythrocytes (107.5 versus 161.0) and was very similar to that in purified parasites (107.5 versus 98.5). Large increases in palmitic acid (C16:0) (from 21.88% to 31.21%) and in oleic acid (C18:1) (from 14.64% to 24.60%), and major decreases in arachidonic acid (C20:4) (from 17.36% to 7.85%) and in docosahexaenoic acid (C22:6) (from 4.34% to 1.8%) occurred as a result of infection. The fatty acid profiles of individual phospholipid classes from IEPM resembled in many instances the fatty acid profiles of parasite phospholipids rather than those of uninfected erythrocytes. Analysis of IEPM from P. falciparum-infected erythrocytes (trophozoite stage) revealed that, during intra-erythrocytic maturation of the parasite, the host erythrocyte phospholipid composition was markedly refashioned. These alterations were not dependent on the method used to isolate the IEPM, with similar results obtained using either a saponin-lysis method or binding to Affigel beads. Since mature erythrocytes have negligible lipid synthesis and metabolism, these alterations must occur as a result of parasite-directed metabolism of erythrocyte lipids and/or trafficking of lipids between the parasite and erythrocyte membranes.
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PMID:Modification of host cell membrane lipid composition by the intra-erythrocytic human malaria parasite Plasmodium falciparum. 200 Dec 27

Erythrocytes infected with the human malaria Plasmodium falciparum produce elevations of the surface membrane of the red cell called knobs. Through the use of transmission electron microscopy and a post-embedding protein A-immunogold technique, it was possible to show changes in the distribution of band 3, glycophorin A and spectrin in the region of the knob. These proteins appeared to be aggregated or condensed in the area of the knob, whereas the remainder of the red cell surface showed no such dense clusters; haemoglobin and the histidine-rich protein of P. lophurae could not be localized to the knobby protuberances. It was not possible to detect any changes in protein distribution using the light microscope and indirect immunofluorescence.
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PMID:Immunofluorescent and immunoelectron microscopic localization of protein antigens in red cells infected with the human malaria Plasmodium falciparum. 297 52

The objective of this study was to determine whether a nonglycosylated portion of glycophorin A (GPA), the main erythrocyte membrane glycoprotein, was involved in the process of invasion of red blood cells (RBC) by merozoites of Plasmodium falciparum, a parasite responsible for the most severe form of malaria. A series of peptides covering the sequence 55-76 situated upstream from the intramembraneous hydrophobic region of GPA was synthesized by an active ester coupling strategy and assessed for invasion-blocking capacity by using an in vitro assay system. Tests showed peptide 65-69, Ala-His-His-Phe-Ser, to be a good inhibitor of the invasion of RBC. Results presented here provide a confirmation of the existence of parasite binding sites on the peptide domain of GPA. Furthermore, comparison of inhibitory activity with peptide composition allowed us to rule out any contribution of a toxic parameter related to hydrophobicity as reported earlier.
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PMID:Malaria invasion of human erythrocytes. Synthesis of peptides relevant to glycophorin A and evaluation of their inhibitory properties. 306 63

Invasion of erythrocytes by malaria parasites involves multiple receptor-ligand interactions. To elucidate these pathways, we made use of four parasite clones with differing specificities for invasion, erythrocytes that are mutant for either glycophorin A or B, and enzyme modification of the erythrocyte surface with neuraminidase and trypsin. Neuraminidase alone abolishes invasion of two parasite clones (Dd2, FCR3/A2); these invade after trypsin treatment alone. A third clone (7G8) is unable to invade trypsin-treated erythrocytes. The fourth clone (HB3) can invade after either neuraminidase or trypsin treatment. The receptor for invasion of trypsin-treated erythrocytes was explored in two ways: treatment of trypsin-treated normal cells with neuraminidase, and trypsin treatment of glycophorin B-deficient cells. Both treatments eliminated invasion by all clones, indicating that the trypsin-independent pathway uses sialic acid and glycophorin B. To identify parasite proteins involved in the different pathways, erythrocyte binding assays were performed with soluble parasite proteins from each clone. Based on binding assays using erythrocytes that lack glycophorin A, the parasite protein known as EBA-175 appears to bind predominantly to glycophorin A. In contrast, the glycophorin B pathway does not appear to involve EBA-175, as binding of EBA-175 was similarly reduced to trypsin-treated normal and trypsin-treated glycophorin B-deficient erythrocytes. Thus, the glycophorin B-dependent, sialic acid-dependent invasion of trypsin-treated normal erythrocytes uses a different parasite ligand, indicating two or more sialic-dependent pathways for invasion. Clone 7G8, which cannot invade trypsin-treated erythrocytes, may be missing the ligand for invasion via glycophorin B.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glycophorin B as an EBA-175 independent Plasmodium falciparum receptor of human erythrocytes. 807 23

Glycophorin A is a major receptor on human erythrocytes for Plasmodium falciparum, the human malaria parasite. In this work, we have produced four glycophorin A-specific mAb: 2B10, 1E4, 3H12, and 3H2. 2B10 was mapped to the amino terminal region of glycophorin (amino acids 1-31), and its binding to erythrocytes was fully dependent on sialic acid residues. 3H2 bound to the region close to the cell membrane, and its binding to Wr (b-) erythrocytes was significantly decreased, compared with its binding to Wr (b+) erythrocytes. 1E4 and 3H12 recognized sites between those identified by 2B10 and 3H2. Pf200 (MSA-1) is a surface protein on the P. falciparum merozoite which has been shown to bind to erythrocytes. By reciprocal inhibition assays, 2B10 and MSA-1 could be shown to share the same determinant on erythrocytes. Using an in vitro assay, we have shown that 2B10 was the most efficient inhibitor of the invasion of human erythrocytes by P. falciparum merozoites. We conclude that the binding site for MSA-1 is primarily located on the amino terminal region, amino acids 1-31, of glycophorin A, and that 2B10 is valuable for additional study of the interactions between P. falciparum merozoites and human erythrocytes.
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PMID:A monoclonal antibody capable of blocking the binding of Pf200 (MSA-1) to human erythrocytes and inhibiting the invasion of Plasmodium falciparum merozoites into human erythrocytes. 839

The invasion of host red blood cells by Plasmodium falciparum merozoites is a complex process requiring multiple receptor-ligand interactions. Glycophorin A, a sialic acid-rich integral membrane protein, is an important RBC receptor for merozoites. We stably expressed glycophorin A in wild type Chinese hamster ovary (CHO) cells and in Lec 2 CHO cells which have a defect in the ability to sialylate proteins. Malaria merozoites were assessed for the ability to adhere to CHO cells that were either untransfected or expressed recombinant glycophorin A. Merozoites only adhered to wild type CHO cells and they did so irrespective of the expression of glycophorin A. These results suggest that cellular adhesion, the earliest event in the malaria invasion process, is mediated by sialic acid residues. This model system will provide valuable molecular information regarding early events in the malaria invasion process.
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PMID:Plasmodium falciparum merozoite adhesion is mediated by sialic acid. 878 Jun 81

A purified Plasmodium falciparum serine protease (gp76) implicated in erythrocyte invasion, degrades human erythrocyte band 3 and glycophorin A. Inhibition studies using synthetic peptides derived from the presumed band 3 enzymatic cleavage sites and the observed uptake of fluorescent phospholipids following gp76 treatment, suggest that band 3 degradation by this serine protease participates in the formation of the parasitophorous vacuole by restructuring the red cell cytoskeleton. These results provide a rationale for the elaboration of specific inhibitors to block red cell invasion by malaria parasites.
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PMID:A role for erythrocyte band 3 degradation by the parasite gp76 serine protease in the formation of the parasitophorous vacuole during invasion of erythrocytes by Plasmodium falciparum. 894 47

Glycophorin A is the major transmembrane sialoglycoprotein of red blood cells. It has been shown to contribute to the expression of the MN and Wright blood group antigens, to act as a receptor for the malaria parasite Plasmodium falciparum and Sendai virus, and along with the anion transporter, band 3, may contribute to the mechanical properties of the red blood cell membrane. Several lines of evidence suggest a close interaction between glycophorin A and band 3 during their biosynthesis. Recently, we have generated mice where the band 3 expression was completely eliminated by selective inactivation of the AE1 anion exchanger gene, thus allowing us to study the effect of band 3 on the expression of red blood cell membrane proteins. In this report, we show that the band 3 -/- red blood cells contain protein 4.1, adducin, dematin, p55, and glycophorin C. In contrast, the band 3 -/- red blood cells are completely devoid of glycophorin A (GPA), as assessed by Western blot and immunocytochemistry techniques, whereas the polymerase chain reaction (PCR) confirmed the presence of GPA mRNA. Pulse-label and pulse-chase experiments show that GPA is not incorporated in the membrane and is rapidly degraded in the cytoplasm. Based on these findings and other published evidence, we propose that band 3 plays a chaperone-like role, which is necessary for the recruitment of GPA to the red blood cell plasma membrane.
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PMID:Complete deficiency of glycophorin A in red blood cells from mice with targeted inactivation of the band 3 (AE1) gene. 949 Jul 2

Malaria male gametocytes within a newly ingested infected blood meal in the mosquito midgut emerge from erythrocytes and extrude approximately eight flagellar microgametes in a process termed exflagellation. In culture, and in blood removed from infected patients, emerging microgametes avidly adhere to neighboring uninfected and infected erythrocytes, as well as to emerged female macrogametes, creating "exflagellation centers". The mechanism of erythrocyte adherence is not known nor has it been determined for what purpose microgametes may bind to erythrocytes. The proposition of a function underlying erythrocyte adherence is supported by the observation of species-specificity in adhesion: microgametes of the human malaria Plasmodium falciparum can bind human erythrocytes but not chicken erythrocytes, whereas avian host Plasmodium gallinaceum microgametes bind chicken but not human erythrocytes. In this study we developed a binding assay in which normal, enzyme-treated, variant or null erythrocytes are identified by a cell surface fluorescent label and assayed for adherence to exflagellating microgametes. Neuraminidase, trypsin or ficin treatment of human erythrocytes eliminated their ability to adhere to Plasmodium falciparum microgametes, suggesting a role of sialic acid and one or more glycophorins in the binding to a putative gamete receptor. Using nulls lacking glycophorin A [En(a-)], glycophorin B (S-s-U-) or a combination of glycophorin A and B (Mk/Mk) we showed that erythrocytes lacking glycophorin B retain the ability to bind but a lack of glycophorin A reduced adherence by exflagellating microgametes. We propose that either the sialic acid moiety of glycophorins, predominantly glycophorin A, or a more complex interaction involving the glycophorin peptide backbone, is the erythrocyte receptor for adhesion to microgametes.
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PMID:Adherence of erythrocytes during exflagellation of Plasmodium falciparum microgametes is dependent on erythrocyte surface sialic acid and glycophorins. 958 38


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