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At least 19 recordsLinked to original sources
PubMed1987

Structural relationships between human erythrocyte sialoglycoproteins beta and gamma and abnormal sialoglycoproteins found in certain rare human erythrocyte variants lacking the Gerbich blood-group antigen(s).

The human erythrocyte membrane sialoglycoproteins beta and gamma are important for the maintenance of the discoid shape of the normal erythrocyte. In this paper we show that the human erythrocyte sialoglycoproteins beta and gamma (hereafter called beta and gamma) are structurally related. Rabbit antisera produced against purified beta and beta 1 and rendered specific to the cytoplasmic portion of these proteins also react with the cytoplasmic portion of gamma. Some human anti-Gerbich (Ge) sera react with the extracellular portion of both beta and gamma. This reactivity is shown to be directed towards a common epitope on beta and gamma. However, most anti-Ge sera do not react with beta, but react with an extracellular epitope only present on gamma. All individuals who lack the Ge antigens lack beta and gamma. In some cases abnormal sialoglycoproteins are present in the erythrocytes, and these are shown to be structurally related to beta and gamma. Rabbit antisera raised against the purified abnormal sialoglycoprotein from a Ge-negative erythrocyte type reacted with the cytoplasmic portion of both beta and gamma. Unlike normal beta and gamma, the abnormal sialoglycoproteins found in Ge-negative erythrocytes migrate as a diffuse band on SDS/polyacrylamide-gel electrophoresis. Studies using endoglycosidases suggest that the diffuse nature of these bands results from carbohydrate heterogeneity and that the abnormal sialoglycoproteins contain N-glycosidically linked oligosaccharides with repeating lactosamine units. Such polylactosamine chains are not present on normal beta or gamma.

Blood Group Antigens↗
PubMed1988

Genetic variants of human red-cell membrane sialoglycoprotein beta. Study of the alterations occurring in the sialoglycoprotein-beta gene.

We have studied the DNA of individuals who express an altered sialoglycoprotein beta on their red cells by using Southern blotting with sialoglycoprotein-beta cDNA probes. Individuals of the Leach phenotype do not express any beta (sialoglycoprotein beta) or gamma (sialoglycoprotein gamma) on their red cells, and we show that about 7 kb of DNA, including the 3' end of the beta gene, is deleted in this DNA. Any protein product of this gene is likely to lack the membrane-associating domain of beta. We have also examined the DNA of two types of other individuals (Yus-type and Gerbich-type) who have red cells that lack beta and gamma, but contain abnormal sialoglycoproteins related to beta. These two types of DNA contain different internal deletions of about 6 kb in the beta gene. We suggest that these deletions result from the presence of two different sets of internal homology in the beta gene, and on this basis we propose structures for the abnormal Yus-type and Gerbich-type sialoglycoproteins which are consistent with the other evidence that is available. We provide evidence that beta and gamma are products of the same gene and suggest a possible mechanism for the origin of gamma based on leaky initiation of translation of beta mRNA.

Amino Acid Sequence↗
PubMed1986

The use of monoclonal antibodies to quantify the levels of sialoglycoproteins alpha and delta and variant sialoglycoproteins in human erythrocyte membranes.

By using radioiodinated monoclonal antibodies we have estimated that there are about 600 000 copies of sialoglycoprotein alpha (synonym glycophorin A) and 80 000 copies of sialoglycoprotein delta (synonym glycophorin B) per normal human erythrocyte. Erythrocytes expressing the product of only one alpha gene contain about 300 000 copies of alpha/cell. Two erythrocyte types containing alpha-delta hybrid molecules were studied. Those with heterozygous expression of the (alpha-delta)Mi.V gene contain about 100 000 alpha-delta copies per cell, whereas those with heterozygous expression of the En(UK) gene contain about 80 000 alpha-delta copies/cell. Erythrocyte types containing delta-alpha hybrid molecules were also studied. About 200 000 copies of (delta-alpha)Dantu were measured in cells with heterozygous expression of the (delta-alpha)Dantu gene (donor M.P.), whereas about 315 000 copies of the putative (delta-alpha)Dantu hybrid were found on the erythrocytes of donor J.O. [which also have heterozygous expression of the putative (delta-alpha)Dantu gene]. The erythrocytes of donor M.P. have normal levels of alpha, whereas those of donor J.O. have only about half-normal levels. It is proposed that the hybrid sialoglycoprotein of donor J.O. is of alpha-delta-alpha composition [(alpha-delta-alpha)Dantu] rather than delta-alpha and results from a double cross-over analogous to that which gives rise to haemoglobin Parchman.

Antibodies, Monoclonal↗
PubMed1985

High frequency antigens of human erythrocyte membrane sialoglycoproteins. I. Ena receptors in the glycosylated domain of the MN sialoglycoprotein.

The specificity of various allo- and autoantibodies, which agglutinate normal erythrocytes, but do not react with En(a-) red cells and normal erythrocytes, treated with trypsin (anti-EnaTS) or ficin (anti-EnaFS), was investigated. Various fragments and modification products of the major (MN) red cell membranes sialoglycoprotein were used in hemagglutination inhibition assays. Six anti-EnaFS sera were found to be directed against the residues approx. 46-56 of the molecule. Five of these require the carbohydrate unit, attached to Thr50, for binding. One anti-EnaTS serum was found to be directed against the residues approx. 36-42. Another antibody with anti-EnaTS specificity was shown to react with the residues 31-39 in some of the MN sialoglycoprotein molecules, namely those not glycosylated at a certain position (probably Thr33). A third anti-EnaTS serum, directed against the sequence domain around Lys30, was also found to react only with a fraction of the molecules, apparently due to the variable attachment of oligosaccharides in that region. The heterogeneity of glycosylation, detected by these two sera, appears to account for the partial tryptic and chymotryptic cleavage in this domain of the MN sialoglycoprotein, which has been described previously. Heterogeneity of the glycosylation at various positions of the molecule could be established by the isolation and analysis of peptides.

Amino Acid Sequence↗
PubMed1979

Abnormal blood-group-Ss-active sialoglycoproteins in the membrane of Miltenberger class III, IV and V human erythrocytes.

1. We have studied the inherited changes occurring in the sialoglycoproteins of membranes from erythrocytes of type Miltenberger Class III (Mi.III), Miltenberger Class IV (Mi.IV) and Miltenberger Class V (Mi.V) by using sodium dodecyl sulphate/polyacrylamide gel electrophoresis and lactoperoxidase radioiodination. 2. Mi.III erythrocytes lack the normal blood-group-Ss-active sialoglycoprotein but contain an unusual s-active sialoglycoprotein of higher apparent molecular weight. A similar abnormal S-active sialoglycoprotein appears to occur in Mi.IV erythrocytes. 3. The Mi.V condition is associated with the hemizygous absence of both the normal blood-group-MN-active sialoglycoprotein and the normal Ss-active sialoglycorprotein. However, a new sialoglycoprotein component is present in these cells that has properties characteristic of both the MN-active and Ss-active sialoglycoproteins. 4. Our results suggest that the new sialoglycorportein present in Mi.V erythrocytes is a hybrid of the normal MN sialoglycoprotein and an s-active sialoglycoprotein that has properties similar to the s-active sialoglycoprotein found in Mi.III erythrocytes. We suggest that the unusual Mi.V sialoglycoprotein is derived from chromosomal misalignment with unequal crossing-over between the genes for the MN- and Ss-active sialoglycoproteins in a manner similar to that which gives rise to haemoglobin Lepore. 5. Further studies of S-s-erythrocytes confirm that these cells lack normal Ss-active sialoglycoprotein, but contain an unusual component that shows some of the properties of the normal Ss-active sialoglycoprotein. 6. Analysis of erythrocytes of type Mk/Mi.III confirms that, in addition to the known hemizygous lack of the MN-active sialoglycoprotein, the Mk condition is also associated with a loss of the Ss-active sialoglycoprotein. 7. In order to facilitate discussion of the complex changes that occur in these variant erythrocytes, a new unified nomenclature is used for the erythrocyte sialoglycoproteins.

Autoradiography↗
PubMed1985

Red cell membrane sialoglycoprotein beta in homozygous and heterozygous 4.1(-) hereditary elliptocytosis.

Sialoglycoprotein beta, a minor sialoglycoprotein of the red cell membrane, was studied in homozygous and heterozygous 4.1(-) hereditary elliptocytosis, a variety of hereditary elliptocytosis characterized by total or partial absence of protein 4.1. Erythrocytes were treated with the periodic acid-NaB3H4 procedure. Following polyacrylamide gel electrophoresis in the presence of SDS, labelled sialoglycoproteins were revealed by fluorography. (i) In the ghosts from the 4.1(-) homozygote, sialoglycoprotein beta was sharply decreased. It is not sure whether the residual material is sialoglycoprotein beta itself, or a distinct sialoglycoprotein migrating in the same place. In long exposure fluorograms, sialoglycoprotein gamma (a sialoglycoprotein related to sialoglycoprotein beta) also turned out to be reduced. In the homozygote's Triton-shells, sialoglycoprotein beta and gamma appeared completely absent. (ii) In the 4.1(-) heterozygote, sialoglycoprotein beta appeared slightly reduced, whereas sialoglycoprotein gamma appeared normal. Both of these proteins were extracted in seemingly normal amounts in the Triton-shells. These observations bring further support to the view that there is an interaction between skeletal membrane protein 4.1 and sialoglycoprotein beta, that is additional to other interactions between the former protein and the lipid bilayer and/or other transmembrane proteins.

Adolescent↗
PubMed1986

Sialoglycoproteins of murine RAW117 large cell lymphoma/lymphosarcoma sublines of various metastatic colonization properties.

A metastatic model for large-cell lymphoma/lymphosarcoma has been developed by sequential selection in vivo of the murine RAW117 cell line for enhanced liver metastasis or in vitro for loss of lectin-binding properties. The metastatic variants obtained from such selections show alterations in cell surface lectin-binding components, such as the wheat germ agglutinin (WGA)-reactive sialoglycoproteins. Detergent lysates from RAW117 cells were analyzed by polyacrylamide gel electrophoresis (PAGE) followed by reaction with 125I-labeled WGA. The [125I]WGA became bound to a diffuse band of Mr 120 000-200 000 in the gels that overlapped with the major sialoglycoprotein band revealed by the periodate-sodium borotritide labeling. However, the [125I]WGA reactivity diminished when gels were pretreated with mild acid to remove sialic acid in situ. The binding of [125I]WGA to the glycoprotein(s) was greater in the high liver-colonizing RAW117-H10 subline than in the parental RAW117-P line. Another lectin with different saccharide specificity, Ricinus communis agglutinin I (RCAI), became bound to a similar class of sialoglycoproteins, as well as to glycoproteins of lower Mr, but only when the gels were pretreated with mild acid to remove sialic acid. These differences in the relative RCAI-binding intensities after chemical removal of sialic acid were similar to those seen with WGA and indicate that differences in WGA reactivity of this class of sialoglycoproteins were not due to increased sialylation of the carbohydrate chains. Sialic acid was removed from RAW117 cells by neuraminidase treatment, and lysates were analysed for [125I]RCAI reactivity after electrophoresis. The migration of the glycoproteins was not affected by neuraminidase, indicating that the diffuseness of the major sialoglycoprotein band was not due to differences in sialylation. [125I]WGA reactivity to the sialoglycoprotein components, before and after Smith degradation in situ, strongly suggests that the oligosaccharide back-bones are highly branched and asparagine-linked. Only the high Mr portion of the diffuse sialoglycoprotein band was stained with peanut agglutinin (PNA) after in situ removal of sialic acid. To determine whether the expression of the sialoglycoprotein was causally related to liver metastasis, the amounts of sialoglycoproteins in RAW117 cells obtained by in vitro selection for increased or decreased metastasis were examined. Binding of [125I]WGA to intact cells and affinity chromatography of vectorially radiolabeled cell surface proteins on WGA-agarose were performed, and the results indicated that the in vitro selected high liver-colonizing RAW117 variants possesses high WGA r

Animals↗
PubMed1980

Blood group MNSs-active sialoglycoproteins of the human erythrocyte membrane.

The human erythrocyte membrane contains at least four different PAS-staining sialic acid-rich glycoproteins. The major sialoglycoprotein, which carries blood group M or N antigen activity, has been extensively characterized. The Ss antigens are located on a minor sialoglycoprotein, which also has "N' activity. The amino acid sequence at positions 1 and 5 of these glycoproteins correlates with the presence of M or N antigen activity. Little is known about the other minor sialoglycoproteins (beta and gamma). Membranes from erythrocytes of type (En(a-)Fin lack the major MN-active sialoglycoprotein; those from S-s-erythrocytes lack normal Ss-active sialoglycoproteins, although they contain an abnormal component that may be an altered Ss glycoprotein. Mk Mk cells lack both the MN- and Ss-active glycoproteins. These sialoglycoprotein-deficient cells are found in apparently healthy individuals. The sera of individuals with sialoglycoprotein-deficient cells may contain antisialoglycoprotein antibody, which has properties similar to those of auto-anti-Pr. Miltenberger Class III, IV, and VI erythrocytes have abnormal Ss-active sialoglycoproteins. Component beta appears altered in Miltenberger Classes I and II. These abnormalities may account for the unique serological properties of Class I, II, III, IV, and VI erythrocytes. Membranes from erythrocytes of type EnU K/Mk, Miltenberger Class V, and Ph contain abnormal sialogylcoproteins that may result from fusion of the genes that give rise to the Mn-and Ss-active sialoglycoproteins. If this is so, then the genes giving rise to the MN and Ss glycoproteins must be adjacent on the same chromosome.

Antibodies↗
PubMed1987

Normal membrane function of abnormal beta-related erythrocyte sialoglycoproteins.

Red cells totally deficient in beta and gamma sialoglycoproteins (the Leach type of Gerbich-negative) are elliptocytic and have altered membrane physical properties as evidenced by marked decreases in both membrane mechanical stability and membrane deformability. Red cells from individuals who are of the Gerbich and Yus phenotypes of Gerbich-negative are also deficient in beta and gamma sialoglycoproteins, but possess abnormal beta-related sialoglycoproteins. In order to determine if these beta-related sialoglycoproteins can functionally substitute for normal sialoglycoproteins, we measured membrane deformability and stability of red cells of the Gerbich and Yus phenotypes. In contrast to the red cells of the Leach phenotype, cells of Gerbich and Yus phenotypes were found to have normal membrane deformability and stability. Moreover, flow cytometric analysis using a monoclonal anti-beta antibody revealed that the Gerbich and Yus phenotype red cells expressed the beta-related sialoglycoprotein to the same extent as its normal counterpart on normal cells. Based on these data, we suggest that the abnormal beta-related sialoglycoproteins can functionally substitute for normal beta and gamma sialoglycoproteins.

Erythrocyte Deformability↗
PubMed1985

Abnormal minor human erythrocyte membrane sialoglycoprotein (beta) in association with the rare blood-group antigen Webb (Wb).

Individuals whose erythrocytes are positive for the rare blood-group antigen Webb (Wb) have an altered form of the minor sialoglycoprotein beta (synonyms glycophorin C and glycoconnectin). This altered sialoglycoprotein beta (beta Wb) has an Mr about 2700 lower than that of normal sialoglycoprotein beta. Treatment of normal sialoglycoprotein beta with endo-beta-N-acetylglucosaminidase F decreased its Mr by about 3600, but similar treatment of sialoglycoprotein beta Wb had no effect. These results suggest the possibility that sialoglycoprotein beta Wb lacks the N-glycosidically linked oligosaccharide found on normal sialoglycoprotein beta.

Blood Group Antigens↗
PubMedDate not supplied

Human red cell antigens. IV. The abnormal sialoglycoprotein of Gerbich-negative red cells.

The minor red cell sialoglycoproteins--beta and gamma (also known as glycophorin C)--are believed to be important to the structural integrity of red cells. The absence of sialoglycoproteins alpha and delta, as seen in En(a-) and S-s-U- cells, respectively, results in cells with normal morphology, but the absence of sialoglycoproteins beta and gamma is associated with elliptocytosis. However, cells that lack Gerbich (Ge) antigens but have an abnormal sialoglycoprotein reactive with antibodies to beta have normal morphology. The authors used a monoclonal antibody specific for beta to explore the nature of this abnormal sialoglycoprotein and its interactions with other membrane proteins. The beta-like sialoglycoprotein of Ge-Yus- red cells appears to react poorly with some antibodies due to steric hindrance by other molecules of sites normally available to immune agglutinins. This steric hindrance is not due to a single interaction with either sialoglycoprotein alpha or delta or band 3. Furthermore, steric hindrance by other molecules does not account for the lack of Ge antigens on these cells.

Antibodies, Monoclonal↗
PubMed1981

Immunochemical evidence for hybrid sialoglycoproteins of human erythrocytes.

The two major sialoglycoproteins of the human erythrocyte membrane (alpha and delta, glycophorins A and B) have identical amino acid sequences for the first 26 residues from the amino terminus, except that alpha expresses M or N blood group antigen activity whereas deta carries only blood group N activity. In addition, the asparagine at position 26 on alpha carries an oligosaccharide chain which is absent from the same position on delta. The two sialoglycoproteins differ in their remaining amino acid sequence and delta expresses blood group Ss activity. There are also variant sialoglycoproteins which have properties of both the alpha and delta molecules and may be hybrids of these. Using antibodies directed against different structural regions of the major sialoglycoprotein alpha, we confirm here and two variant erythrocytes (Miltenberger class V (MiV) and Ph) contain hybrid sialoglycoprotein molecules (Fig. 1). These hybrid sialoglycoproteins arise from cross-over events between the genes coding for alpha and delta. It is suggested that the two genes are closely associated in the order alpha, delta (5' leads to 3') on the chromosome.

Amino Acid Sequence↗
PubMed1984

Individuals lacking the Gerbich blood-group antigen have alterations in the human erythrocyte membrane sialoglycoproteins beta and gamma.

Membranes from erythrocytes with a new Gerbich (Ge)-negative phenotype (Leach phenotype), as well as those from two other Ge-negative phenotypes, were examined. Whereas cells of the Leach phenotype apparently lack three minor sialoglycoproteins (beta, beta 1 and gamma), the membranes of Ge- Yus- and Ge- Yus+ erythrocytes apparently lack beta- and gamma-sialoglycoproteins but contain additional diffusely migrating components of apparent Mr 30 500-34 500 and 32 500-36 500 respectively. Immunoprecipitation experiments showed that the abnormal components of both Ge- Yus- and Ge- Yus+ erythrocytes reacted with two monoclonal antibodies, BRIC 4 and BRIC 10. These antibodies have been shown to react with sialoglycoproteins beta and beta 1 in normal erythrocytes. Cytoskeletal preparations from Ge- Yus- and Ge- Yus+ erythrocyte membranes contained the abnormal components. In contrast with cells of the Leach phenotype, which are elliptocytic, Ge- Yus- and Ge- Yus+ were of normal shape, despite their apparent lack of beta- and gamma-sialoglycoproteins. It seems likely that the abnormal components in these cells contribute to their normal shape. Ovalocytic erythrocytes were shown to incorporate more radioactivity in the sialoglycoprotein-beta 1 region than normal erythrocytes after labelling by the periodate/NaB3H4 technique. It is suggested that abnormal components in Ge- Yus- and Ge- Yus+ erythrocytes result from chromosomal misalignment with unequal crossing-over at meiosis between the genes giving rise to beta-, beta 1- and gamma-sialoglycoproteins.

Antibodies, Monoclonal↗
PubMed1977

Inherited sialoglycoprotein deficiencies in human erythrocytes of type En[a-].

We have investigated the membranes of erythrocytes from a family in which there is a genetic defect [previously described as the En[a-] condition[ resulting in the loss of the major erythrocyte sialoglycoprotein [PAS-i]. The results show that two different types of sialoglycoprotein deficiency can be distinguished within this family. We suggest that the En[a-] group of variants is more appropriately described as a class of sialoglycoprotein deficient erythrocytes. Using a new technique it is shown that the blood group M antigen of normal erythrocytes is found only on the erythrocyte sialoglycoprotein while in this family the M antigen is found on membrane components other than the sialoglycoprotein. Our results suggest that the amino acid sequence of the sialoglycoprotein is important in defining the difference between the blood group M and N antigens in normal erythrocytes.

Aminosalicylic Acid↗
PubMed1985

Altered membrane sialoglycoproteins in human erythrocytes lacking the Gerbich blood group antigens.

The sialoglycoproteins (glycophorins) in human red cell membranes of rare individuals lacking totally (Ge-1,-2,-3 phenotype) or partially (Ge-1,-2,3 phenotype) the Gerbich (Ge) blood group antigens and two Ge-1,-2,-3 heterozygotes were studied by dodecylsulfate polyacrylamide gel electrophoretic techniques. Two sialoglycoproteins (components D and E) were not detectable in the membranes from the homozygotes and found to be decreased by about 50% in those from the heterozygotes. Ge--1,-2,-3 and Ge-1,-2,3 cells were found to contain a 'new' component (mol. masses about 29 and 30 kDa, respectively) possibly representing a D/E hybrid molecule. This sialoglycoprotein was not detectable in membranes from the Ge-1,-2,-3 heterozygotes, suggesting that the Ge-1,-2,-3 phenotype may be caused by at least two different alleles at the Ge blood group antigen locus. Hemagglutination or hemagglutination inhibition tests involving anti-Ge 1,2,3 and -Ge 1,2 as well as native and enzyme-treated normal red cells (phenotype Ge 1,2,3) or membrane and sialoglycoprotein fractions from normal erythrocytes indicate that the receptors of these sera are located within the glycosylated domain(s) of the D and/or E sialoglycoprotein(s). Our data suggest that the Ge locus encodes the polypeptide sequences of the D and E sialoglycoproteins.

Blood Group Antigens↗
PubMed1986

The inheritance of abnormal sialoglycoproteins found in a Gerbich negative individual.

The Gerbich blood group antigens are probably expressed on one or more of the minor erythrocyte (beta, beta 1, or gamma) sialoglycoproteins which are lacking in some rare individuals having the Gerbich negative phenotype. A monoclonal antibody, CMRF-10, which recognises a trypsin-sensitive site on both the beta and beta 1 sialoglycoproteins, was tested for binding to erythrocytes from a Gerbich negative individual, OM. Erythrocytes from OM bound CMRF-10 in similar amounts to normal erythrocytes even though membranes from OM were shown by sodium dodecyl sulphate-polyacrylamide gel electrophoresis to lack both the beta and gamma sialoglycoproteins found in normal red blood cells. Instead, abnormal sialoglycoproteins which migrated as two bands with apparent molecular weights within the range 29,500-32,500 daltons were identified and purified using CMRF-10. Subsequent electrophoretic analysis of OM's two children failed to reveal any abnormal sialoglycoproteins. This suggests that in this instance the Gerbich negative phenotype may result from other mechanisms, possibly defective glycosylation, rather than a crossover involving the gene coding for the primary protein structure of the sialoglycoproteins.

Aged↗
PubMed1991

Distribution of sialic acid between sialoglycoproteins and other membrane components of different erythrocyte phenotypes.

The sialic acid content of erythrocytes of three different AB0 blood groups have been studied. The sialic acid contents of erythrocyte membranes containing 300 mg protein were determined and compared. Groups 0 (Rhesus negative), AB (both Rhesus negative and positive), and B (Rhesus negative) blood differed significantly (p less than 0.05) in total sialic acid content and in the distribution of sialic acid between sialoglycoproteins and other membrane components. Membrane materials containing 300 mg total protein showed sialic acid contents of 52.73 +/- 2.2 mumol sialic acid for group 0 (Rhesus negative) 34.77 +/- 1.16 mumol for group AB (Rh negative), 32.88 +/- 1.52 mumol for AB (Rh positive) and 21.23 +/- 0.84 mumol for B (Rh negative). In group 0 (Rh. neg.) membranes 39.4 +/- 1.4% of the total sialic acid was associated with the sialoglycoproteins. The percentage of sialic acids associated with sialoglycoproteins in other erythrocyte membranes were 77.7 +/- 1.3% for group B, and 55.6 +/- 1.0% and 56.4 +/- 1.8% for group AB (Rh. negative) and (Rh. positive) respectively. The changes appear to be independent of the Rhesus grouping but dependent on the AB0 grouping since membranes of the two Rhesus types of group AB had identical total sialic acid and sialoglycoproteins sialic acids. The sialic acid densities in sialoglycoproteins also differed from one erythrocyte type to another. Group 0 (Rh. negative) membrane sialoglycoproteins had sialic acid density of 140.5 +/- 3.1 nmol/mg compared to 71.7 +/- 1.2 nmol/mg for group B and 128.1 +/- 2.2 and 124.5 +/- 4.0 nmol/mg for group AB Rhesus negative and Rhesus positive respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

ABO Blood-Group System↗
PubMed1988

Differential expression of a sialoglycoprotein with an approximate molecular weight of 900,000 on metastatic human colon carcinoma cells growing in culture and in tumor tissues.

Wheat germ agglutinin (WGA)-binding cellular glycoproteins produced by HT-29 human colon carcinoma and its variant cells established from liver metastases in nude mice after intrasplenic injection were analyzed by polyacrylamide gel electrophoresis. On 5.5% polyacrylamide gels five major sialoglycoproteins (approximate Mr 115,000, 145,000, 190,000, 450,000, and 740,000) reactive with WGA were common to the parental and metastatic sublines. There was an additional component of Mr approximately 900,000 that was prominent in cells established from liver metastases. Specific removal of sialic acid from the glycoproteins eliminated WGA binding, indicating that all the WGA-binding glycoproteins including the Mr 900,000 component were sialoglycoproteins. Smith degradation following mild acid hydrolysis resulted in formation of WGA-binding carbohydrate chains on Mr 115,000, 145,000, 190,000, and 900,000 components, but not on Mr 450,000 and 740,000 components, which indicated that these two sialoglycoproteins bore different oligosaccharides from the other sialoglycoproteins. The Mr 900,000 component was more prominent with HT-29 cells growing in nude mice than those growing in vitro. WGA binding to the Mr 900,000 component of metastasis-derived HT-29 cells growing in a nude mouse was higher than that of parental cells growing in nude mice. The expression in liver metastases derived from parental as well as metastatic cells was higher than the primary tumor growing in the spleen of the same mouse, indicating that the levels of Mr 900,000 sialoglycoprotein (SGP = 900) were regulated by intrinsic and environmental factors. The influence of organ microenvironmental factors was confirmed by analyzing sialoglycoproteins of HT-29 cells growing in the liver of a nude mouse following intrahepatic injection. Analyses of human colorectal carcinoma tissues and liver metastases revealed a polydisperse WGA-reactive high-molecular-weight component similar to that seen in tumors growing in nude mice. The mean value of WGA binding to high-molecular-weight glycoproteins in the primary tumors of stage B1 patients was smaller than that of all other primary tumors. Comparison of primary tumors with liver metastases from the same patients indicated that the level of SGP-900-like high-molecular-weight glycoproteins in metastases was not always higher than those in primary tumors.

Adenocarcinoma↗