Biosynthesis of the major human red cell sialoglycoprotein, glycophorin A, in a continuous cell line

Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology

Solute carriers form one of three major superfamilies of membrane transporters in humans, and include uniporters, exchangers and symporters. Following several decades of molecular characterisation, multiple solute carriers that form obligatory heteromers with unrelated subunits are emerging as a distinctive principle of membrane transporter assembly. Here we comprehensively review experimentally established heteromeric solute carriers: SLC3-SLC7 amino acid exchangers, SLC16 monocarboxylate/H⁺ symporters and basigin/embigin, SLC4A1 (AE1) and glycophorin A exchanger, SLC51 heteromer Ost α-Ost β uniporter, and SLC6 heteromeric symporters. The review covers the history of the heteromer discovery, transporter physiology, structure, disease associations and pharmacology - all with a focus on the heteromeric assembly. The cellular locations, requirements for complex formation, and the functional role of dimerization are extensively detailed, including analysis of the first complete heteromer structures, the SLC7-SLC3 family transporters LAT1-4F2hc, b^0,+AT-rBAT and the SLC6 family heteromer B⁰AT1-ACE2. We present a systematic analysis of the structural and functional aspects of heteromeric solute carriers and conclude with common principles of their functional roles and structural architecture.

Valid Presumption of Shiga Toxin-Mediated Damage of Developing Erythrocytes in EHEC-Associated Hemolytic Uremic Syndrome

The global emergence of clinical diseases caused by enterohemorrhagic Escherichia coli (EHEC) is an issue of great concern. EHEC release Shiga toxins (Stxs) as their key virulence factors, and investigations on the cell-damaging mechanisms toward target cells are inevitable for the development of novel mitigation strategies. Stx-mediated hemolytic uremic syndrome (HUS), characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute renal injury, is the most severe outcome of an EHEC infection. Hemolytic anemia during HUS is defined as the loss of erythrocytes by mechanical disruption when passing through narrowed microvessels. The formation of thrombi in the microvasculature is considered an indirect effect of Stx-mediated injury mainly of the renal microvascular endothelial cells, resulting in obstructions of vessels. In this review, we summarize and discuss recent data providing evidence that HUS-associated hemolytic anemia may arise not only from intravascular rupture of erythrocytes, but also from the extravascular impairment of erythropoiesis, the development of red blood cells in the bone marrow, via direct Stx-mediated damage of maturing erythrocytes, leading to “non-hemolytic” anemia.

High-level genomic integration, epigenetic changes, and expression of sleeping beauty transgene

Sleeping Beauty transposon (SB-Tn) has emerged as an important nonviral vector for integrating transgenes into mammalian genomes. We report here a novel dual fluorescent reporter cis SB-Tn system that permitted nonselective fluorescent-activated cell sorting for SB-Tn-transduced K562 erythroid cells. Using an internal ribosome entry site element, the green fluorescent protein (eGFP) was linked to the SB10 transposase gene as an indirect marker for the robust expression of SB10 transposase. Flourescence-activated cell sorting (FACS) by eGFP resulted in significant enrichment (>60%) of cells exhibiting SB-Tn-mediated genomic insertions and long-term expression of a DsRed transgene. The hybrid erythroid-specific promoter of DsRed transgene was verified in erythroid or megakaryocyte differentiation of K562 cells. Bisulfite-mediated genomic analyses identified different DNA methylation patterns between DsRed(+) and DsRed(-) cell clones, suggesting a critical role in transgene expression. Moreover, although the host genomic copy of the promoter element showed no CpG methylation, the same sequence carried by the transgene was markedly hypermethylated. Additional evidence also suggested a role for histone deacetylation in the regulation of DsRed transgene. The presence of SB transgene affected the expression of neighboring host genes at distances >45 kb. Our data suggested that a fluorescent reporter cis SB-Tn system can be used to enrich mammalian cells harboring SB-mediated transgene insertions. The observed epigenetic changes also demonstrated that transgenes inserted by SB could be selectively modified by endogenous factors. In addition, long-range activation of host genes must now be recognized as a potential consequence of an inserted transgene cassette containing enhancer elements.

Chapter 6 Protein Sorting in the Secretory Pathway

This chapter focuses on protein sorting in the secretory pathway. From primary and secondary biosynthetic sites in the cytosol and mitochondrial matrix, respectively, proteins and lipids are distributed to more than 30 final destinations in membranes or membrane-bound spaces, where they carry out their programmed function. Molecular sorting is defined, in its most general sense, as the sum of the mechanisms that determine the distribution of a given molecule from its site of synthesis to its site of function in the cell. The final site of residence of a protein in a eukaryotic cell is determined by a combination of various factors, acting in concert: (1) site of synthesis, (2) sorting signals or zip codes, (3) signal recognition or decoding mechanisms, (4) cotranslational or posttranslational mechanisms for translocation across membranes, (5) specific fusion-fission interactions between intracellular vesicular compartments, and (6) restrictions to the lateral mobility in the plane of the bilayer. Improvements in cell fractionation, protein separation, and immune precipitation procedures in the past decade have made them possible. Very little is known about the mechanisms that mediate the localization and concentration of specific proteins and lipids within organelles. Various experimental model systems have become available for their study. The advent of recombinant DNA technology has shortened the time needed for obtaining the primary structure of proteins to a few months.

Importance of molecular studies on major blood groups--intercellular adhesion molecule-4, a blood group antigen involved in multiple cellular interactions

Several blood groups, including the LW-blood group were discovered in the first part of last century, but their biochemical characteristics and cellular functions have only more recently been elucidated. The LW-blood group, renamed ICAM-4 (CD242), is red cell specific and belongs to the intercellular adhesion molecule family. ICAM-4 binds to several integrin receptors on blood and endothelial cells and is thus able to form large cellular complexes containing red cells. Its physiological function(s) has remained incompletely understood, but recent work shows that macrophage integrins can bind red cells through this ligand. In this article we discuss molecular properties of major blood group antigens, describe ICAM-4 in more detail, and show that phagocytosis of senescent red cells is in part ICAM-4/beta(2)-integrin dependent.

Intracellular and Cell Surface Localization of a Complex between αMβ2 Integrin and Promatrix Metalloproteinase-9 Progelatinase in Neutrophils

We have recently demonstrated that promatrix metalloproteinases (proMMPs), particularly proMMP-9, are potent ligands of the leukocyte beta(2) integrins. We studied here the complex formation between proMMP-9 and alpha(M)beta(2), the major MMP and integrin of neutrophils. On resting neutrophils, the proMMP-9/alpha(M)beta(2) complex was primarily detected in intracellular granules, but after cellular activation it became localized to the cell surface, as demonstrated by immunoprecipitation and double immunofluorescence. Further indication of the complex formation was that neutrophils and alpha(M)beta(2)-transfected L cells, but not the wild-type L cells or leukocyte adhesion deficiency cells, bound to immobilized proMMP-9 or its recombinant catalytic domain in a beta(2) integrin-dependent manner. Peptides that bound to the alpha(M) integrin-I domain and inhibited its complex formation with proMMP-9 prevented neutrophil migration in a transendothelial assay in vitro and in a thioglycolate-elicited peritonitis in vivo. These results suggest that the translocating proMMP-9/alpha(M)beta(2) complex may be part of the cell surface machinery guiding neutrophil migration.

Lipid metabolism in tumour bearing mice treated withAeromonas L-asparaginase

The anticancerous drug isolated in our laboratory from estuarineAeromonas was characterised and is found to be an enzyme, L-asparaginase. The antileukaemic effect of this drug was studied in mice by inducing leukaemia with Ehrlich ascites cell lines. It was compared with commercially available drug, Leunase, isolated fromE. coli. The lipid profiles in mice during leukaemia and under treatment was studied. The decreased levels of cholesterol and increased levels of triglycerides and phospholipids in serum, liver and kidney were observed in tumour bearing mice. Significant changes in the above values were observed with enzyme therapy. It could bring some of the values to near normal level. L-asparaginase fromAeromonas was found to be more effective.

Expression of transcription factors during sodium phenylacetate induced erythroid differentiation in K562 cells

During 15 days of treatment of K562 cells with sodium phenylacetate, we observed an increase in the cellular hemoglobin concentration with a similar increase in the expression of gamma-globin mRNA. Morphological studies demonstrated characteristic features of erythroid differentiation and maturation. At the same time there was no change in the level of expression of the cell surface antigenes CD33, CD34, CD45, CD71 and glycophorin A. Likewise, the level of expression of the erythroid transcription factors GATA-1, GATA-2, NF-E2, SCL and RBTN2, all expressed in untreated K562 cells, did not increase during sodium phenylacetate induced erythroid differentiation. The expression of the nuclear factors Evi-1 and c-myb, known to inhibit erythroid differentiation, did not decrease. We conclude that sodium phenylacetate treatment of K562 cells increases gamma-globin mRNA and induces cell maturation as judged by morphology without affecting the expression of the erythroid transcription factors, some of which are known to be involved in the regulation of beta-like globin genes.

The proteoglycan perlecan is expressed in the erythroleukemia cell line K562 and is upregulated by sodium butyrate and phorbol ester

Perlecan is a modular heparan sulfate proteoglycan that harbors five domains with homology to the low density lipoprotein receptor, epidermal growth factor, laminin and neural cell adhesion molecule. Using a monoclonal antibody directed against the laminin-like domain of perlecan, we have recently shown that perlecan is widely expressed in all lymphoreticular systems. To investigate further this observation we have studied the expression of perlecan in two human leukemic cell lines. Using reverse transcriptase-PCR, ribonuclease protection assay, and metabolic labeling we detected significant perlecan expression in the multipotential cell line K562, originally derived from a patient with chronic myelogenous leukemia. In contrast, the promyelocytic cell line HL-60 expressed perlecan at barely detectable levels. These results were intriguing because the K562 cells do not assemble or produce a classical basement membrane. Following induction with either sodium butyrate or the phorbol diester 12-0-tetradecanoylphorbol-13-acetate (TPA), K562 and HL-60 differentiate into early progenitor cells with erythroid or megakaryocytic properties, respectively. Following treatment of K562 and HL-60 cells with either of these agents, perlecan expression was markedly increased in K562 cells. In contrast, we could detect perlecan protein synthesis in HL-60 cells only at very low levels, even after induction with TPA or sodium butyrate. Collectively, these results indicate that perlecan is actively synthesized by bone marrow derived cells and suggest that this proteoglycan may play a role in hematopoietic cell differentiation.

Quantitative comparison between aminophospholipid translocase activity in human erythrocytes and in K562 cells

Spin-labeled phospholipids were used to determine the transbilayer movement of phospholipids in human erythrocytes, in K562 cells and in human neonatal red cells. The erythroleukemia cell line, K562, as well as human neonatal red cells, which are rich in reticulocytes, were considered as representative of human erythrocyte precursor cells. In the nucleated cells, the difference between outside-inside movement of aminophospholipids and that of phosphatidylcholine or sphingomyelin analogues allowed us to discriminate between lipid internalization due to aminophospholipid translocase activity and to endocytosis. From the initial rates of aminophospholipid inward movement, we inferred that the activity of the aminophospholipid translocase is higher in the precursor cells than in mature erythrocytes.

Major O-glycosylated sialoglycoproteins of human hematopoietic cells: differentiation antigens with poorly understood functions

All human hematopoietic cells seem to contain a major, heavily O-glycosylated sialoglycoprotein. Glycophorin A is specific for the erythroid lineage of cells, and leukocytes have a major sialoglycoprotein, also called leukosialin or sialophorin. Cell differentiation results in patterns of O-glycosylation in these proteins, which reflect the stage of differentiation within a cell lineage as well as lineage specificity. The altered carbohydrate compositions may influence the interactions of the cells with external ligands. Healthy individuals lacking glycophorin A in their red cells are known, whereas a deficiency of the leukocyte sialoglycoprotein may result in immunological disease. Although little is known about the physiological functions of these proteins, they form interesting models for studies on regulation of glycosylation, biosynthesis of O-glycosylated glycoproteins, and function of cell surface receptors.

Cell lines and peripheral blood leukocytes derived from individuals with chronic myelogenous leukemia display virtually identical proteins phosphorylated on tyrosine residues

An aberrant p210BCR-ABL protein that possesses constitutive protein-tyrosine kinase activity is presumed to be involved in the development of the neoplastic phenotype in chronic myelogenous leukemia (CML). Using a highly specific antibody against phosphotyrosine, we have isolated the tyrosine-phosphorylated p210BCR-ABL and several other proteins containing phosphotyrosine from a variety of CML cell lines. p210BCR-ABL isolated by the monoclonal anti-phosphotyrosine antibody possessed protein-tyrosine kinase activity in vitro comparable to that of the p210BCR-ABL isolated by antibody to a specific peptide sequence in the ABL protein-tyrosine kinase. Other prominent proteins containing phosphorylated tyrosine residues were observed at 185, 150, 120, 105, 63, 56, 36, and 32 kDa, and less prominent proteins were observed at 195, 155, 94, 53, 40, and less than 29 kDa. Staphylococcal V8 peptide mapping indicated that proteins of similar molecular weights were highly homologous to each other across cell lines, despite the diverse hematopoietic lineages of these cells and the genetic heterogeneity of the patients from whom the CML cell lines were derived. Phosphopeptide mapping also revealed that these proteins were distinct from each other as well as from p210BCR-ABL. Because virtually identical phosphotyrosine-containing proteins were found in peripheral blood leukocytes taken directly from CML patients, these proteins are not an artifact of long-term tissue culture but appear to be an integral part of the CML phenotype.

Ph1-positive CML-derived myeloid-monocytoid precursor cell line producing substance(s) that stimulates normal CFU-C

A new Ph1-chromosome positive cell line, KOPM-28. was established from a patient with chronic myelogenous leukemia (CML) in blast crisis. KOPM-28 cells were phenotypically immature: without azurophilic granules; negative for myeloperoxidase and positive for specific and nonspecific esterases. The nonspecific esterase reaction was intensified by TPA, and retinoic acid reinforced the specific esterase reaction without inducing morphological changes. KOPM-28 cells were not phagocytic. The cells expressed complement receptors, myeloid-monocytoid antigens, an Ia-like antigen and T4 antigen. CALLA, T-lymphocyte specific antigens, B-lymphocyte related antigen and platelet-megakaryocyte-megakaryoblast specific antigen were not detected. KOPM-28 cells formed colonies in semi-solid medium; this ability was augmented by GM-CSA. The addition of culture medium conditioned by KOPM-28 cells to normal bone marrow cells resulted in the increase of the CFU-C colonies. These findings indicate that KOPM-28 cells have features of myeloid and monocytoid precursor cells and that they are producing substance(s) which stimulates normal CFU-C.

A 93-kDa glycoprotein expressed on human cultured monocytes and dendritic reticulum cells defined by an anti-K562 monoclonal antibody

An IgG2a monoclonal antibody, referred to as 12B1 and raised against the K562 cell line, reacted with adherent monocytes maintained in culture for several days but not with bone marrow or peripheral blood cells including freshly isolated monocytes. Among human leukemic cell lines, 12B1 reacted essentially with the promyelocytic HL60 cell line. 12-O-Tetradecanoylphorbol 13-acetate treatment, but no other differentiation inducer, strongly enhanced its reactivity on K562, HL60 and the histiocytic U937 cell line. Immunoperoxidase staining of sections of normal human tissues showed that 12B1 specifically recognized dendritic reticulum cells in germinal centers of lymph nodes, spleen and tonsils. The 12B1-detected antigen is a highly glycosylated polypeptide of an apparent molecular mass of 93-86 kDa. The 12B1 antigen appears to be a new glycoprotein marker shared by adherent monocytes and dendritic reticulum cells. The association of the 12B1 epitope with cells which present antigen and/or exert accessory function suggests that this molecule could play a role in these activities.

Golgi and secreted galactosyltransferase

Galactosyltransferase (GT) belongs to the glycosyltransferases. In several tissues and cell lines, the enzyme is localized by immunocytochemistry to the two to three trans cisternae of the Golgi complex and may thus be considered a specific membrane component of this type of endomembrane. As a consequence, it is the most common Golgi "marker" enzyme in cell fractionation studies. Study of its biosynthesis, membrane orientation, and turnover in several tissues and cultured cell lines has broadened our knowledge about Golgi function itself. The enzyme is oriented towards the lumen of the cisternal space. In this orientation, it catalyzes the transfer of galactose to glycoprotein-bound acetylglucosamine and, in the presence of alpha-lactalbumin, to glucose, as shown in the Golgi complex of mammary gland epithelial cells. The enzymatic properties of GT are well known. The metabolism of GT has been extensively studied in HeLa and human hepatoma cells. The enzyme is synthesized in the rough endoplasmic reticulum (RER) and provided with one N-linked oligosaccharide and palmitate residues. In the Golgi complex, terminal sugars are attached to the N-linked oligosaccharide and extensive O-glycosylation takes place. The half-life of the enzyme is about 20 hr, after which a soluble form appears in the culture medium. Release of GT into the medium is observed in all cell lines studied. This phenomenon is in accordance with the presence of soluble GT in body fluids such as serum, ascites, milk, and saliva. In patients suffering from ovarian and breast cancer, increased levels of GT enzyme activity have been reported. Whether extracellular GT is of biological significance is still a point of discussion.

Lysosome-associated membrane proteins: characterization of LAMP-1 of macrophage P388 and mouse embryo 3T3 cultured cells

Lysosome-associated membrane protein (LAMP)-1, a major glycoprotein of mouse embryo 3T3 cells and specifically associated with the lysosomal membrane, has been identified in P388 macrophage cells and compared with the homologous glycoprotein of NIH 3T3 cells. Immunofluorescence microscopy with anit-LAMP-1 monoclonal antibodies shows that the antigen was distributed throughout P388 cells including the ruffled edges or pseudopodia, identical to the pattern of acridine orange accumulation. LAMP-1 was purified from P388 cells by affinity chromatography with 1D4B monoclonal antibody, yielding a homogeneous glycoprotein comprising 0.1% of the total detergent-extracted cell protein. The apparent mass of P388 LAMP-1 was 130,000 to 150,000 compared to the 3T3 glycoprotein of 105,000 to 115,000. Analysis of tryptic peptides indicated that the two purified glycoproteins were highly homologous. Protein synthesis was analyzed in a variety of cell lines by pulse-chase labeling with [35S]methionine; in every case, LAMP-1 was synthesized as a precursor of apparent Mr 92,000, and then converted to heterogeneous mature forms differing in average Mr from 110,000 to 140,000. The basis for these apparent differences in mass was examined by studies of the biosynthesis and oligosaccharide composition of the glycoprotein. Core polypeptides of 45,000 Da were obtained from both HaNIH and P388 cells by treating immunoprecipitates of [35S]methionine pulse-labeled molecules with endoglycosidase H. Cells treated with monensin contained heterogeneous molecules of 80,000 to 85,000 Da. Isoelectric heterogeneity of mature LAMP-1 was markedly reduced by treatment with neuraminidase whereas there was little effect on the apparent molecular weight of the molecules or the differences between the various cell lines. beta-D-Xyloside inhibition of glycosaminoglycan synthesis had little effect on the apparent mass of LAMP-1.

Glycophorin A on normal and leukemia cells detected by monoclonal antibodies, including a new monoclonal antibody reactive with glycophorins A and B

A new hemagglutinating monoclonal antibody, MoAb31, detected glycophorins A and B in Western blots. Results with enzyme-modified erythrocytes indicated the MoAb31 determinants were sialic acid dependent, and resided on glycophorin A on the trypsin-resistant, ficin-sensitive segment, and on glycophorin B on the ficin-sensitive segment. Another new monoclonal antibody, MoAb36, detected the Wrb antigen, located on the non-glycosylated segment of glycophorin A near its insertion into the lipid bilayer. Immunofluorescent staining of normal hematopoietic and leukemia cells with these and other monoclonal antibodies to glycophorin A demonstrated glycophorin A on erythroid cells only. Cytofluorograph analysis showed the majority of cells of the erythroleukemia cell lines K562 and HEL expressed glycophorin A, as indicated by reactivity with the monoclonal glycophorin A antibodies R10, R18, 6A7 and 10F7. However, reactivity with monoclonal antibodies to glycosylated determinants (MoAb31 and R1.3) and to the non-glycosylated segment near the membrane insertion (MoAb36, and R7.1) was reduced or absent. Expression of "missing" glycophorin A antigens on K562 and HEL could not be induced using a variety of chemical and biologically active modifiers. We conclude that glycophorin A of erythroleukemia cell lines K562 and HEL differs from glycophorin A at the surface of normal, mature erythrocytes with respect to reactivity with monoclonal glycophorin A antibodies.

Identification of the major human sialoglycoprotein from red cells, glycophorin AM, as the receptor for Escherichia coli IH 11165 and characterization of the receptor site

The pyelonephritogenic Escherichia coli strain 1 H 11165 specifically agglutinates human erythrocytes carrying the M blood group antigen. The polymorphic forms of this antigen, M and N, are located in the NH2-terminal region of the major human red-cell sialoglycoprotein, glycophorin A. Radioactively labeled glycophorin A from M cells specifically bound to the bacteria. Purified glycophorin AM, but not glycophorin AN, efficiently inhibited for binding. Mild periodate treatment oxidized the NH2-terminal serine in glycophorin AM and this resulted in loss of binding to the bacteria. High concentrations of serine and alkali-labile oligosaccharides derived from glycophorin AM inhibited the binding, whereas the synthetic M-specific NH2-terminal pentapeptide Ser-Ser-Thr-Thr-Gly did not. Neuraminidase treatment of glycophorin AM did not destroy the binding. The most efficient inhibition of binding was observed with the N-terminal glyco-octapeptide obtained from glycophorin AM by CNBr cleavage. This peptide contains both the essential serine residue and the alkali-labile oligosaccharides, which both are recognized by the bacterium.

A cyclic AMP binding protein pattern useful as a biochemical differentiation marker of erythroleukemic cell lines and normal cloned erythroblasts

Previous study of a variety of a human hemopoietic cell lines and normal samples with 8-N3-[32P]-cAMP photoaffinity labelling, SDS-polyacrylamide gel electrophoresis and autoradiography revealed five distinct cAMP binding protein patterns, each of which were restricted to cells of particular lineages. One pattern unique to K562 cells was characterized by the presence of three bands designated a, b and d. In order to ascertain the significance of this finding, we studied by the same methods normal human erythroblasts harvested from methylcellulose cultures of fetal liver and adult blood, and murine and human erythroleukemic cells (MEL and HEL) as well as K562, cultured with and without chemical inducers of erythrodifferentiation. Three band patterns recognizable as similar to that of K562, but distinctive from those of myeloid and lymphoid cells, were noted of cells of erythroblastic origin. Both HEL and MEL, as well as the normal erythroblasts, exhibited heaviest labeling of band a in contrast to K562, which exhibited heaviest labelling of band d. Relative labelling of band b and d of HEL and MEL increased following treatment with 50 mu hemin or 4 mM hexamethylenebisacetamide (HMBA), respectively. Treatment of K562 with hemin, however, resulted in increased band a. Thus, among hemopoietic cells, an isozymic cAMP binding protein pattern has been identified which is characteristic of the erythroid lineage. The relative abundances of the three components (a, b and d) have been furthermore noted to undergo a series of shifts during induced differentiation. Cyclic AMP binding proteins may thus prove useful as a biochemical marker system in the recognition and analysis of erythroid differentiation.

Epitopes immunologically related to glycophorin A on human malignant and non-malignant cells in culture

Nine monoclonal antibodies specific to different antigenic determinants on the cyanogen bromide fragments CNBr3 (1-8) and CNBr1 (9-81) of glycophorin A, the major sialoglycoprotein of human red blood cells, were used for the detection of similar or cross-reactive epitope(s) on nucleated somatic cells. A panel of human malignant and non-malignant cells consisting of erythroleukemia, melanoma and carcinomas of breast, cervix, larynx, nasopharynx and colon, as well as human fibroblasts and mammary cells, were tested using a sensitive enzyme-linked immunoassay. The presence of glycophorin-like epitopes were demonstrated, in varying concentrations, on all cells tested. These epitropes were found to be localized on the cell membranes by indirect immunofluorescence.

Differentiation of human erythroid cells is associated with increased O-glycosylation of the major sialoglycoprotein, glycophorin A

Glycophorin A, the major human erythrocyte sialoglycoprotein, is found exclusively on cells of the erythroid lineage. The amino acid sequence is known, and glycophorin A isolated from mature erythrocytes contains a single N-glycosidic and 15 O-glycosidic oligosaccharides. Monoclonal antibodies against erythrocyte glycophorin A reacted weakly with erythroid precursors while a monospecific rabbit antiserum reacted strongly with immature and mature red cells. Glycophorin A was isolated from cells representing various stages of erythropoiesis in normal bone marrow, from blood cells of neonates with erythroblastosis fetalis, and from the erythroleukemic cell lines K562 and HEL before and after induced differentiation. Analysis of the oligosaccharides showed less O-glycosylation of glycophorin A in erythroid precursors. The degree of glycosylation increased concomitantly with differentiation.

Induction of erythroid differentiation in K562 cells and natural killer cell-mediated lysis: distinct effects at the level of recognition and lysis in relation to target cell proliferation

The erythroleukemic K562 cell line was induced to erythroid differentiation by a variety of agents, including hemin, bleomycin, and cytosine arabinoside. The sensitivity of induced cells to binding and lysis by non-sensitized peripheral blood mononuclear cells (MNC) in agarose was studied in relation to the target cell division rate. Differentiated K562 cells formed a lower proportion of conjugates with MNC, when compared with non-induced controls. The reduction correlated significantly with the level of differentiation, irrespective of the inducer and the proliferative status. The differentiation-induced alterations of lysis, however, were strongly influenced by the modification of target cell growth rate which was caused by the differentiating agent. These data suggest that target cell differentiation has distinct effects upon the steps of recognition and lysis by natural killer cells.

Interferon induction in human mixed leukocyte-tumor-cell reactions: evidence for restriction to a certain lineage expressing glycophorin A

This study reports the induction of interferon (IFN) in human mononuclear cells (MNC) by hematopoietic tumor cells. Only 3 out of 15 cell lines were capable of inducing IFN in the mixed leukocyte/tumor-cell reaction (MLTR). K562, a pluripotent stem cell line and DUTKO-I, a hybrid between K562 and Daudi (Burkitt lymphoma) induced high levels of antiviral activity (ranging from 50-440 units IFN/ml). PUTKO-I, a hybrid between K562 and P3HR-I (Burkitt lymphoma) induced very low levels of IFN (10 units/ml). This antiviral activity was produced by HLA-DR + adherent cells as revealed by different cell separation techniques, and shared well-known properties of IFN gamma (isoelectric point, inactivation by anti-human IFN gamma antibodies; species-restricted protection). MLTR-induced IFN induction could be blocked by enzyme treatment of tumor cells, but was still present when glutaraldehyde-fixed cells were used for induction. Analysis of the cells by flow cytometry for expression of glycophorin A (GpA) revealed that expression of GpA correlated with the ability to induce antiviral activity in MLTR. Furthermore, isolated GpA could be used as a stimulant as well and the response to either K562 cells or soluble GpA was enhanced up to ten-fold by the addition of a GpA-specific monoclonal antibody.

Accumulation of a heat shock-like protein during differentiation of human erythroid cell line K562

The human erythroid cell line K562 provides a model system for studying erythroid differentiation and eukaryotic gene regulation. These cells express glycophorin A, spectrin and i antigen. They accumulate embryonic and fetal haemoglobins on induction of erythroid differentiation with haemin, sodium butyrate or hydroxyurea. In the present study, the protein composition of K562 cells during haemin-mediated induction of erythroid maturation was analysed by two-dimensional gel electrophoresis. Under conditions in which haemin did not effect cell viability and proliferation, a protein of approximately 70,000 molecular weight (MW) accumulated in the differentiated K562 cells. The accumulation appears to be due to an increase in the rate of RNA synthesis for this protein. The protein is related in sequence to a 70,000-MW heat shock protein. An antigenically related protein was also demonstrated in human bone marrow and accumulates at particular stages of human erythroid maturation.

Cytochemical localization of terminal N-acetyl-D-galactosamine residues in cellular compartments of intestinal goblet cells: implications for the topology of O-glycosylation

The O-linked oligosaccharides of mucin-type glycoproteins contain N-acetyl-D-galactosamine (GalNAc) that is not found in N-linked glycoproteins. Because Helix pomatia lectin interacts with terminal GalNAc, we used this lectin, bound to particles of colloidal gold, to localize such sugar residues in subcellular compartments of intestinal goblet cells. When thin sections of low temperature Lowicryl K4M embedded duodenum or colon were incubated with Helix pomatia lectin-gold complexes, no labeling could be detected over the cisternal space of the nuclear envelope and the rough endoplasmic reticulum. A uniform labeling was observed over the first and several subsequent cis Golgi cisternae and over the last (duodenal goblet cells) or the two last (colonic goblet cells) trans Golgi cisternae as well as forming and mature mucin droplets. However, essentially no labeling was detected over several cisternae in the central (medial) region of the Golgi apparatus. The results strongly suggest that core O-glycosylation takes place in cis Golgi cisternae but not in the rough endoplasmic reticulum. The heterogenous labeling for GalNAc residues in the Golgi apparatus is taken as evidence that termination of certain O-oligosaccharide chains by GalNAc occurs in trans Golgi cisternae.

Intracellular transport of influenza virus hemagglutinin to the apical surface of Madin-Darby canine kidney cells

The intracellular pathway followed by the influenza virus hemagglutinin (HA) to the apical surface of Madin-Darby canine kidney cells was studied by radioimmunoassay, immunofluorescence, and immunoelectron microscopy. To synchronize the migration, we used a temperature-sensitive mutant of influenza WSN, ts61, which, at the nonpermissive temperature, 39.5 degrees C, exhibits a defect in the HA that prevents its exit from the endoplasmic reticulum. Upon transfer to permissive temperature, 32 degrees C, the HA appeared in the Golgi apparatus after 10 min, and on the apical surface after 30-40 min. In the presence of cycloheximide, the expression was not inhibited, indicating that the ts defect is reversible; a wave of HA migrated to the cell surface, where it accumulated with a half time of 60 min. After passage through the Golgi apparatus the HA was detected in a population of smooth vesicles, about twice the size of coated vesicles, located in the apical half of the cytoplasm. These HA-containing vesicles did not react with anti-clathrin antibodies. Monensin (10 microM) delayed the surface appearance of HA by 2 h, but not the transport to the Golgi apparatus. Incubation at 20 degrees C retarded the migration to the Golgi apparatus by approximately 30 min and blocked the surface appearance by acting at a late stage in the intracellular pathway, presumably at the level of the post-Golgi vesicles. The initial appearance of HA on the apical surface was in the center; no preference was observed for the tight-junctional regions.

Glycophorin A expression in malignant hematopoiesis

Two hundred twenty-nine patients with hematopoietic malignancies were tested for reactivity with a monoclonal anti-human glycophorin A antibody. One hundred twenty-three of these cases were classified as acute leukemias of either the myeloid, lymphoid, erythroid, or undifferentiated type. The monoclonal antibody we used (VIE-G4) was obtained after immunization with a human thymocyte suspension. It selectively reacts with glycophorin A (GpA) and strongly binds to 40% of K-562 cells and all morphologically recognizable erythroid precursor cells. Apart from two cases with acute erythroid leukemia, this antibody reacted with none of the malignant cells in the 229 tested hematopoietic malignancies, including the 121 nonerythroid acute leukemias. This finding seems to contradict the earlier observations by L. Andersson and colleagues that a considerable proportion of acute leukemias express GpA on their surface. One reason for this discrepancy might be the fact that VIE-G4 detects only complete glycosylated GpA. If this is the sole explanation, this would mean that the poorly differentiated cells in these cases express incompletely glycosylated GpA.

N-acetylgalactosaminyltransferase activity involved in O-glycosylation of herpes simplex virus type 1 glycoproteins

We report on N-acetylgalactosaminyltransferase (UDPacetylgalactosamine--protein acetylgalactosaminyltransferase; EC 2.4.1.41) activity in herpes simplex virus type 1 (HSV-1)-infected BHK and RicR14 cells, a line of ricin-resistant BHK cells defective in N-acetylglucosaminyltransferase I. The enzyme catalyzed the transfer of [14C]N-acetylgalactosamine (GalNAc) from UDP-[14C]GalNAc into HSV glycoproteins, as identified by immunoprecipitation. The sugar was selectively incorporated into the immature forms of herpesvirus glycoproteins pgC, pgD, and gA-pgB, which are known to contain N-linked glycans of the high-mannose type. The high incorporation of [14C]GalNAc into endogenous acceptors of HSV-1-infected RicR14 cells was consistent with the accumulation of immature forms of HSV glycoproteins which occurs in these cells. Mild alkaline borohydride treatment of glycoproteins labeled via GalNAc transferase showed that the transferred GalNAc was O-linked and represented the first sugar added to the peptide backbone.

Reduced temperature prevents transfer of a membrane glycoprotein to the cell surface but does not prevent terminal glycosylation

The transport kinetics of the influenza virus hemagglutinin from its site of synthesis to the apical plasma membrane of Madin-Darby canine kidney cells, a polarized epithelial cell line, were studied by a sensitive tryptic assay. Hemagglutinin acquired terminal sugars, as judged by sensitivity to endo-beta-N-acetylglucosaminidase H, 10-15 min after synthesis, and first appeared on the apical domain 15 min later. None of the pulse-labeled hemagglutinin accumulated on the basolateral domain. At 20 degrees C, terminal glycosylation continued, but no hemagglutinin was detected on the cell surface within 2 hr. If the incubation temperature was raised from 20 degrees C to 37 degrees C, hemagglutinin was quickly externalized, demonstrating that the inhibition at low temperature was reversible.

K562 cell anion exchange differs markedly from that of mature red blood cells

Human K562 leukemic cells exhibit several erythroid properties, including synthesis and expression of the major red blood cell sialoglycoprotein, glycophorin. This has led us to ask if these cells express a functional anion transport system analogous to that which is associated with the other major erythrocyte glycoprotein, band 3. The chloride-36 exchange flux in K562 cells is less than 0.6% of that which would be expected in mature erythrocytes under similar conditions. Unlike red blood cells, K562 cells do not exhibit a high chloride-sulfate selectivity, and various agents that inhibit red blood cell chloride exchange are all much less effective in K562 cells. On the basis of these flux measurements, K562 cells probably contain less than 600 fully functional red blood cell-like band 3 molecules per cell, in contrast to about a million molecules in the mature red blood cell. The possible-existence of greatly altered band 3 molecules with a reduced turnover rate and/or a reduced affinity for chloride and for various inhibitors is unlikely but cannot be completely excluded. Anion transport was also measured in K562 cells that had been induced to increase hemoglobin synthesis by various chemical agents. Even under these conditions, chloride fluxes indicated no substantial increase in the number of functional anion transport sites or their chloride transport rate.

Lithium enhances growth of human leukaemia cells in vitro

Lithium is known to cause leucocytosis in normal humans, and lithium salts have been used therapeutically in attenuating leucopenia in patients undergoing chemotherapy. Recent reports also described leukaemia development during lithium treatment. We have investigated the effect of lithium chloride on the proliferation of human myeloid, erythroblastic, and T- and B-lymphoblast leukaemia cells in vitro. Colony formation by cells of the myeloid leukaemia lines HL-60 and KG-1 was enhanced by lithium chloride, and maximal stimulation was seen at 5 X 10(-4) M. Lithium also increased the proliferation of KG-1a cells, a subline of KG-1 cells that does not respond to colony-stimulating factor, indicating a direct growth-promoting effect on myeloid leukaemia cells. Lithium was found to enhance colony formation by the T-lymphoblast cell line MOLT 4 and the B-lymphoblast line IM-9 at concentrations between 10(-6) and 10(-3) M. The addition of lithium chloride to murine Friend or human K-562 erythroleukaemia cells also caused an augmentation in colony formation. These observations may have relevance to the therapeutic use of lithium in patients with haematological malignancies.

HEL cells: a new human erythroleukemia cell line with spontaneous and induced globin expression

A new human erythroleukemia cell line has been established. This line, designated HEL, is capable of spontaneous and induced globin synthesis, producing mainly G gamma and A gamma chains. Embryonic chains (epsilon, zeta) and alpha chains are detectable in very small amounts; beta chains are undetectable. This line provides a new model system for studying aspects of erythroid cell differentiation and differential globin gene expression.

Enzymatic modification of the surface carbohydrates of Friend erythroleukemic cells

Surface carbohydrates of Friend erythroleukemic-cells were modified by treatment with the exoglycosidases, alpha-galactosidase, beta-galactosidase, and neuraminidase without affecting cell growth and viability either in the presence of absence of 1.8% DMSO as inducer. When cells were incubated with a combination of alpha-galactosidase and neuraminidase and then induced, they showed an increased rate of differentiation as measured by the formation of benzidine-positive cells. These enzymes used singly, or beta-galactosidase treatment alone, or in combination with neuraminidase, did not change the rate of differentiation. Cell-surface labeling and electrophoretic separation of the glycoconjugates revealed that two regions of approximate molecular weights of 195,000 and 185,000 were neuraminidase-sensitive and one other of molecular weight of about 75,000 was sensitive to alpha-galactosidase. Both untreated and the combined alpha-galactosidase, neuraminidase-modified cells exhibited the same rate of uptake of carbon-14 DMSO, ruling out the possibility that the observed increased rate of differentiation was due to faster penetration of DMSO into enzyme-treated cells. On the other hand, the decrease in the rate of uptake of rubidium-86, an analogue of K+, by treated-induced cells was significantly enhanced over that observed with untreated-induced cells, suggesting that alpha-galactosidase plus neuraminidase modification of the cell surface was affecting at least one of the early events occurring in the Friend erythroleukemic cell differentiation program.