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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
Role of Tumor Cell Membrane in Hyperthermia
Published in Leopold J. Anghileri, Jacques Robert, Hyperthermia In Cancer Treatment, 2019
Many biological functions are attributed to the heteroglycan moiety of glycoproteins, the most prominent being its involvement in recognition,101,102 and as already mentioned, its importance in protein folding and stabilization of the cell membrane. Glycoproteins also play a role in determining selective permeability of the cell membrane. In myocardium, the permeability to calcium ions is controlled by the concentration of sialic acid of specific glycoprotein of the plasma membrane, and this is done without affecting its permeability to potassium ions.103,104 In a general way, sialoglycoprotein has been suggested to play an important role in membrane permeability through regulation of calcium binding.105
Malaria
Published in F. Y. Liew, Vaccination Strategies of Tropical Diseases, 2017
Michael J. Lockyer, Anthony A. Holder
A number of lines of evidence have implicated erythrocyte sialic acid as a ligand for P. falciparum merozoites.11 Heterogeneity in the requirement for this ligand between different strains of P. falciparum has been demonstrated from studies on the invasion of neuraminidase- treated erythrocytes, and led to the model that P. falciparum merozoites possess two receptors for erythrocyte binding — one dependent on a sialic acid ligand and the second on a sialic acid-independent and trypsin-sensitive ligand.11 Since most sialic acid of the erythrocyte sialoglycoproteins is carried by the glycophorins, particularly glycophorin A (GpA), attempts have been made to show the importance of these components in the invasion process. Evidence to support the role of the glycophorins has been contradictory, however,11,53 and the interpretation of invasion inhibition studies using competitive addition of carbohydrates (N-acetyl-D-glucosamine, GpA) or Mabs against GpA is complicated by the effects of toxicity and membrane deformability, respectively.11
The epidemiological and clinical characteristics of patients with young-onset genetic Creutzfeldt-Jakob disease
Published in Neurological Research, 2023
Daniel Safadi, Oren S Cohen, Joab Chapman, Hanna Rosenmann, Zeev Nitsan, Esther Kahan, Shmuel Appel, Marwan Alkrenawi
Transmissible spongiform encephalopathies (TSEs) are a group of neurodegenerative disorders found in many mammals [1]. TSE in human, include Creutzfeldt – Jakob disease (CJD), Gerstmann – Straüssler – Sheinker syndrome (GSS), kuru, and fatal familial insomnia (FFI). The molecular pathogenesis of the disease is a conformational transformation of the normal membrane-associated sialoglycoprotein PrP (referred to as PrPC) that undergoes a post-translational conformational modification into the pathological structure of PrPSc. PrPSc has a protease-resistant core and contains substantial amounts of β sheet, whereas PrPC is largely α-helical and is sensitive to protease digestion [2,3] The accumulation of this abnormal prion protein leads to neuronal degeneration, astrocytic gliosis, and spongiform change [4].
Treatment and outcome of Philadelphia chromosome-positive acute lymphoblastic leukemia in adults after relapse
Published in Expert Review of Anticancer Therapy, 2020
Marie Balsat, Victoria Cacheux, Martin Carre, Emmanuelle Tavernier-Tardy, Xavier Thomas
CD22 is a 135-kDa sialoglycoprotein that mediates intercellular interactions for sialic-acid bearing ligands and modulates antigen receptor signaling and B-cell activation. CD22 is an important B cell-restricted surface antigen that is expressed in 96% of B cell-lineage ALL [103]. It is rapidly internalized on binding to anti-CD22 making it an attractive target for targeted therapy with chemotherapeutic conjugates. Following the development of gemtuzumab ozogamicin, an anti-CD33 antibody-drug conjugate, in acute myeloid leukemia, inotuzumab ozogamicin, an anti-CD22 antibody-drug conjugate, was developed. Inotuzumab ozogamicin is a humanized MoAb against CD22 conjugated via a bi-functional linker to a potent cytotoxic agent calicheamicin derived from Micromonospora echinospora, which induces DNA double-strand breaks and apoptosis independent of cell cycle progression [104]. Upon binding to CD22 receptors, inotuzumab is rapidly internalized, trafficked through lysosomes leading to hydrolysis of inactive calicheamicin. Calicheamicin is then reduced to its active form by intracellular glutathione. In the nucleus, active calicheamicin binds to DNA and generates free radicals leading to DNA double-strand breaks and cellular apoptosis (Figure 2).
Erythrocytic membrane anionic charge, sialic acid content, and their correlations with urinary glycosaminoglycans in preeclampsia and eclampsia
Published in Scandinavian Journal of Clinical and Laboratory Investigation, 2020
Papia Sen, Debdatta Ghosh, Chandan Sarkar
Several other studies have clarified the role of heparan sulfate as providing a negative charge to the GBM through the infusion of specific enzymes such as heparinase that are capable of selectively depleting the GBM of heparan-associated negative charges, resulting in the appearance of abnormal amounts of albumin in the urine [26]. The neutralization of anionic sites within the glomerular capillary wall is associated with a loss of charge-dependent glomerular permselectivity. Sialoglycoproteins and GAGS are known to be major determinants of the anionic charge in biological membranes as demonstrated by studies on glomerular and erythrocytic membranes [27]. Therefore, our finding of a negative correlation between EAC and UGAGS and a positive correlation between EAC with EMSA substantiates the above-mentioned propositions.