New procedures for glycophorin A purification with high yield and high purity

A Comprehensive Review of Our Current Understanding of Red Blood Cell (RBC) Glycoproteins

Human red blood cells (RBC), which are the cells most commonly used in the study of biological membranes, have some glycoproteins in their cell membrane. These membrane proteins are band 3 and glycophorins A-D, and some substoichiometric glycoproteins (e.g., CD44, CD47, Lu, Kell, Duffy). The oligosaccharide that band 3 contains has one N-linked oligosaccharide, and glycophorins possess mostly O-linked oligosaccharides. The end of the O-linked oligosaccharide is linked to sialic acid. In humans, this sialic acid is N-acetylneuraminic acid (NeuAc). Another sialic acid, N-glycolylneuraminic acid (NeuGc) is present in red blood cells of non-human origin. While the biological function of band 3 is well known as an anion exchanger, it has been suggested that the oligosaccharide of band 3 does not affect the anion transport function. Although band 3 has been studied in detail, the physiological functions of glycophorins remain unclear. This review mainly describes the sialo-oligosaccharide structures of band 3 and glycophorins, followed by a discussion of the physiological functions that have been reported in the literature to date. Moreover, other glycoproteins in red blood cell membranes of non-human origin are described, and the physiological function of glycophorin in carp red blood cell membranes is discussed with respect to its bacteriostatic activity.

Alterations in erythrocyte membrane protein composition in advanced non-small cell lung cancer

Cancer can be associated with hematological complications related to red blood cell (RBC) function, whose physiological roles have now been expanded since it is now known that RBC are also signalling cells. The aim of this study was to explore the alterations occurring in the protein composition of RBC in advanced non-small cell lung cancer (NSCLC). Blood samples from 21 patients with advanced (stages III-IV) NSCLC (16 squamous cell carcinomas and 5 adenocarcinomas), and from 21 healthy volunteers were used. Samples from 6 randomly selected patients and 6 controls were used for the screening of erythrocyte ghost alterations by Differential Scanning Calorimetry (DSC). Samples from 15 patients and 15 controls, different from those used in the DSC measurements, were randomly selected for analysis of the expression of glycophorin (GP) species, band 3, and glycoproteins by SDS-PAGE and Western blotting or lectin enzyme immunoassays. Additionally, 5 patients with chronic obstructive pulmonary disease (COPD) were used as a control group representative of a benign inflammatory disease. Blood samples from the COPD patients were used to analyze the expression of GPs, band 3 and syaloglycoproteins. We observed the following in NSCLC: (a) changes in GP expression levels, mainly decreases in the GPA and GPC monomers, and in the GPAB dimers; (b) a decrease in the band 3 protein level, and (c) alterations in the expression of different sialoglycoproteins. RBC from the COPD patients also showed protein abnormalities, some of them, especially at the level of band 3 and the syaloglycoproteins, being similar to those in NSCLC.

Carbohydrates borne on human glycophorin A are recognized by porcine Kupffer cells

BACKGROUND

We have previously shown that when porcine livers are perfused with human blood, porcine Kupffer cells extract up to 3 units of human erythrocytes over the course of a 72 hr perfusion. We have previously hypothesized that the recognition event responsible for this interaction involves a lectin receptor on the surface of the porcine Kupffer cell interacting with a carbohydrate epitope on the surface of the human erythrocytes.

METHODS

Treatments to disrupt the protein core of purified glycoproteins from the surface of human erythrocytes included: pronase, trypsin, beta-mercaptoethanol (2-ME), and heating to 90 degrees . Alternatively, we have removed the carbohydrate residues from purified human red blood cell (RBC) glycoproteins using glycosidases. Erythrocyte binding in the presence or absence of treated glycoproteins was quantified by Chromium-labeled RBC recognition by primary cultures of porcine Kupffer cells.

RESULTS

Human, but not porcine, erythrocytes were bound by in vitro primary cultures of porcine Kupffer cells. Binding was inhibited by preincubation of porcine Kupffer cells with purified human erythrocyte glycoproteins (hEGP) from human erythrocyte membranes. Pretreatment of human EGP with pronase, trypsin, 2-ME, or heating did not interfere with the ability of human EGP to inhibit the binding of human erythrocytes to porcine Kupffer cells. Deglycosylation of the purified hEGP completely disrupted hEGP ability to inhibit the binding of human erythrocytes to porcine Kupffer cells.

CONCLUSION

We conclude that porcine Kupffer cells bind xenogeneic human RBC by recognition of a carbohydrate epitope on the surface of human erythrocytes. We hypothesize that this binding is mediated by a porcine Kupffer cell lectin receptor.