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Hemolytic Anemia Associated with Red Cell Membrane Defects
Published in Harold R. Schumacher, William A. Rock, Sanford A. Stass, Handbook of Hematologic Pathology, 2019
A multitude of mutations that cause HE have been identified in several different genes that encode proteins of the erythrocyte membrane skeleton (Fig. 1). The most common mutations causing HE are found in genes for α and β spectrin. These mutations, found mostly in blacks, produce spectrin dimers with defective ability to self-associate into tetramers. Deficient or dysfunctional protein 4.1 is produced by another group of HE mutations. Glycophorin C deficiency, the result of several different mutations, can also give rise to HE. SAO is the consequence of a mutation in band 3.
Inherited Disorders of Red Cell Membrane Proteins
Published in Ronald L. Nagel, Genetically Abnormal Red Cells, 2019
There are three major sialoglycoproteins in the red cell, glycophorins A, B, and C. Each of these proteins has its N-terminal, glycosylated domain on the outside of the cell, a hydrophobic transmembrane region, and a hydrophilic cytoplasmic portion. The glycosylated regions bear the blood group antigens and binding sites for a variety of parasites which invade the red cell. These proteins are generally not visible on polyacrylamide gels stained with Coomassie blue, but can be seen if periodic acid-Schiff stain is used. Glycophorin A is the most abundant glycophorin, and the best characterized. This protein probably exists as a dimer in the cell,50 and binds to protein 3.51 The cytoplasmic domain contains a group of negatively charged amino acids which appear to play an important function in binding to negatively charged phospholipids52,53 and protein 4.1.54 However, the structural significance of these interactions is unclear since individuals with the blood types En (a — ), who have no glycophorin A, and those homozygous for Mk, who have neither glycophorin A nor B, have normal red cell morphology and no anemia.55,56 Individuals who lack glycophorin C have the blood group phenotype Gerbich negative (Ge —), and have hereditary ellipto-cytosis as will be described below.90
The Red Blood Cell In Thalassemia *
Published in Ronald L. Nagel, Genetically Abnormal Red Cells, 2019
Eliezer Rachmilewitz, Ariella Oppenheim, Oded Shalev
A lower content of sialic acids, which may be an important determinant in RBC survival,112-115 has been found in thalassemic RBC membranes, particularly in those which were obtained from untransfused patients.116 The decrease in sialic acids was 25% and was accompanied by an uneven distribution of the remaining 75% residues along the thalassemic RBC membrane. The loss of sialic acids occurred from the receptor domain of glycophorines on the outer surface of the membrane.117 It is noted that the glycophorin from young thalassemic RBC was fully sialated, and that the loss took place during circulation in the peripheral blood. Sialidase-mediated degradation was probably not the cause of the alterations in sialic acids in the thalassemic RBC.117 Although the cause of the decrease and uneven distribution of sialic acids along the thalassemic membrane is still unknown, the observation of these changes stimulated further studies on the possible interaction between the cell membrane and the cells of the reticuloendothelial system (RES).
Cutaneous-hemolytic loxoscelism following brown recluse spider envenomation: new understandings
Published in Clinical Toxicology, 2020
Justin K. Loden, Donna L. Seger, Henry A. Spiller, Li Wang, Daniel W. Byrne
The second mechanism involves PLD activity on metalloproteinases. The erythrocyte plasma membrane contains heavily glycosylated proteins, the most prevalent being glycophorin-A, which ensure erythrocyte survival by preventing spontaneous complement deposition. Erythrocyte exposure to Loxosceles PLD results in the activation of an unspecified endogenous metalloproteinase that cleaves extracellular portions of glycophorin-A. This enhances C3b deposition to the erythrocyte membrane and initiates the alternative complement pathway resulting in hemolysis [36–38]. Glycophorin-A cleavage and complement-mediated hemolysis activity is transferred from toxin-exposed erythrocytes to toxin-naïve erythrocytes, which explains the extent of hemolysis observed after envenomation [38]. In vitro incubation of L. reclusa venom with erythrocytes revealed statistically significant reduction in glycophorin-A expression and could be used as a biomarker of venom exposure [39].
A novel EPB41 p.Trp704* mutation in a Korean patient with hereditary elliptocytosis: a case report
Published in Hematology, 2020
Soyoung Shin, Kyung-Ah Hwang, Kyuhyun Paik, Joonhong Park
HE occurs in 0.3–0.5 per 1000 newborns, and patients are asymptomatic in about 90% of cases [9]. Approximately 95% of patients with HE have a mutation in genes responsible for α- and β-spectrin expression, i.e. polypeptides which in tetrameric form compose the basis of the cell cytoskeleton [6]. Mutations associated with the protein 4.1 and glycophorin C are rare [6]. Patients with a mutation on only one allele are asymptomatic, while in cases when it is bilateral suffer moderate or more severe hemolytic anemia [6,9]. In addition, the hereditary nature of the disorder is also supported by the absence of elements indicating other conditions that are associated with the presence of elliptocytes, such as deficiencies in iron, folic acid, or vitamin B12 [9].
Computational modeling – an approach to the development of blood grouping reagents
Published in Expert Review of Hematology, 2021
Serena Ekman, Robert Flower, Ross T Barnard, Alison Gould, Xuan T Bui
Kalli and Reithmeier [24] in 2018 applied molecular dynamics simulations to existing crystal structures for Band 3 and Glycophorin A and demonstrated the dynamic interaction between the two proteins. They showed that Glycophorin A promotes Band 3 clustering, and provided a model for the mechanism behind the biological functions associated with Glycophorin A and Band 3.