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J S Rush

Publications and source records attributed to J S Rush.

36 records · Page 2Linked to original sources
PubMed1992

An anion-exchange radioassay for glucose 6-phosphate phosphatase: use in topological studies with endoplasmic reticulum vesicles.

A simple procedure is presented for the enzymatic preparation of [2-3H]mannose 6-phosphate (Man 6-P) with purified yeast hexokinase and unlabeled ATP. The enzymatically synthesized [2-3H]Man 6-P is utilized as the radiolabeled substrate in a new rapid assay for glucose 6-phosphate (Glc 6-P) phosphatase. The principle of the assay procedure is that the unreacted substrate, [2-3H]Man 6-P, is retained by the anion-exchange resin, AG 1-X8 (acetate), while the enzymatic product, [2-3H]-mannose, is eluted directly into a scintillation counting vial. When Glc 6-P phosphatase activity associated with mouse liver endoplasmic reticulum (ER) vesicles is assayed by the new chromatographic assay, the same characteristic latency and properties are observed, as determined by the commonly used colorimetric assay of inorganic phosphate produced. The anion-exchange radioassay described should be useful for a variety of topological studies on enzymes associated with membrane vesicles derived from liver and kidney ER.

Animals↗
PubMed1992

Direct assay of membrane-associated protein kinase C activity in B lymphocytes in the presence of Brij 58.

This paper describes a simple and direct procedure for assaying Ca(2+)-dependent protein kinase C (PKC) activity in membrane fractions isolated from purified murine B lymphocytes (B cells) treated with phorbol 12-myristate 13-acetate (PMA). The results indicate that membrane-bound PKC in B cells, treated with PMA, can be measured directly in the presence of 0.5% Brij 58 by assaying the transfer of 32P from [gamma-32P]ATP to histone type III-S. This method obviates the need for partial purification of the protein kinase by ion-exchange chromatography prior to assaying PKC activity. The properties of membrane-associated PKC activity in B cells have been characterized, and the kinetics of PMA-induced translocation of PKC in cultured murine B cells, the rat glial tumor clone C6, and primary neonatal osteoblastic cells have been defined by this direct assay. The results obtained with B cells and the other cell lines indicate that this direct assay procedure could be useful for studies on the factors controlling PKC translocation in a variety of cultured mammalian cells.

Adenosine Triphosphate↗
PubMed1991

Biogenesis of the endoplasmic reticulum in activated B lymphocytes: temporal relationships between the induction of protein N-glycosylation activity and the biosynthesis of membrane protein and phospholipid.

An earlier report from this laboratory documented a substantial increase in the rates of dolichol-linked oligosaccharide intermediate synthesis and protein N-glycosylation in purified murine splenic B lymphocytes (B cells) activated by treatment with bacterial lipopolysaccharide (LPS). In this study the developmental patterns for the induction of lipid-mediated protein N-glycosylation, membrane protein, and phosphatidylcholine (PC) biosynthesis were compared during the proliferative response of B cells to LPS. By electron microscopy it could be seen that a distinct endoplasmic reticulum (ER) network began to develop by 24-48 h after exposure of the purified B cells to LPS. The rate of synthesis of membrane protein increased markedly during the first 10 h after activation, reaching a maximum at 30-40 h. The induction of protein N-glycosylation was delayed slightly relative to membrane protein synthesis, with glycoprotein synthesis increasing sharply approximately 20 h after activation. When phospholipid synthesis was monitored by measuring [CH3-3H]choline incorporation into PC, the rate of labeling increased slowly during the first 35 h, but more substantially between 35 and 90 h. The incorporation of labeled choline into PC was drastically reduced by 5'-deoxy-5'-isobutylthio-3-deazaadenosine, an inhibitor of CDP-choline synthesis, indicating that the incorporation of radiolabeled choline is primarily a measurement of the rate of de novo synthesis of PC. In vitro assays revealed that while choline kinase activity was virtually unchanged, CDP-choline synthetase activity increased gradually throughout the activation period. Diacylglycerol cholinephosphotransferase activity, an ER-associated enzyme, was present at low levels between 0 and 35 h, but increased fivefold between 35 and 90 h. On the basis of the developmental patterns for the rates of protein N-glycosylation, membrane protein insertion, and PC biosynthesis determined by metabolic labeling experiments, we tentatively conclude that all of the ER-associated membrane proteins involved in these biosynthetic processes are not induced concurrently during the activation of B cells by LPS.

Animals↗
PubMed1991

Expression of dolichol-linked saccharide intermediate synthesis during the development of B lymphocytes.

There are large developmental increases in the rates of dolichol-linked oligosaccharide synthesis and protein N-glycosylation when resting murine splenic B lymphocytes are activated by bacterial lipopolysaccharide (LPS). These in vivo and in vitro studies were carried out to investigate the underlying biochemical mechanisms involved in the dramatic increase in the rate of oligosaccharide-lipid biosynthesis in LPS-stimulated B cells. Metabolic labelling experiments showed that the rate of synthesis of N-acetyl-glucosaminylpyrophosphoryldolichol (GlcNAc-P-P-Dol), mannosylphosphoryldolichol (Man-P-Dol) and glucosylphosphoryldolichol (Glc-P-Dol) increased 4- to 15-fold between 20 and 40 h after exposure to LPS. When the glycosyltransferase activities catalysing the formation of the three dolichol-bound monosaccharides were assayed in vitro with endoplasmic reticulum (ER)-enriched fractions, the initial rates were found to be elevated 4-fold prior to the major increases in oligosaccharide-lipid intermediate biosynthesis observed in vivo. Based on kinetic analyses, the higher enzyme activities were due to an increase in the amount of the three glycosyltransferases in activated cells. The time courses for elevated cellular content and rate of synthesis of guanosine-diphosphomannose (GDP)-Man corresponded to the developmental increase in oligosaccharide-lipid synthesis. The kinetics and magnitude of the induction of oligosaccharide-lipid synthesis were similar whether the initial rates were calculated on the basis of [2-3H]mannose-labelling or the specific activity of the GDP-[2-3H]mannose pool.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Golgi-enriched membrane fractions from rat brain and liver contain long-chain polyisoprenyl pyrophosphate phosphatase activity.

The subcellular distribution of polyisoprenyl pyrophosphate phosphatase activity has been examined in rat brain by assaying the release of 32Pi from [beta-32P]dolichyl pyrophosphate (Dol-P-P) as described previously (Scher,M.G. and Waechter, C.J. (1984) J. Biol. Chem., 259, 14580-14585). The highest specific activities of Dol-P-P phosphatase in rat brain were found in the Golgi-enriched light microsomal, synaptic plasma membrane and heavy microsomal fractions. A comparative analysis of the distribution of galactosyltransferase and dolichol kinase reveals that Dol-P-P phosphatase activity co-fractionates with galactosyltransferase activity, and that the high level found in the Golgi-enriched fraction is not due to cross-contamination with heavy microsomes. When beta-labelled C95 Dol-P-P and the C95 allylic polyisoprenyl pyrophosphate (Poly-P-P) were compared as substrates for the Golgi-enriched light microsomal and heavy microsomal fractions, similar Km values were calculated for the two pyrophosphorylated substrates for each membrane fraction. Based on these kinetic analyses, the enzyme(s) catalysing this reaction do not distinguish between substrates containing saturated or allylic alpha-isoprene units. When Dol-P-P phosphatase activity was assessed in submicrosomal fractions obtained from rat liver by two separate procedures, the highest specific activity was also detected in the Golgi-enriched fraction. While the specific activities for Dol-P-P phosphatase and sialyltransferase were in the relative order of Golgi greater than smooth endoplasmic reticulum (ER) greater than rough ER, the relative order of dolichol kinase was rough ER greater than smooth ER greater than Golgi.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Characterization and localization of a long-chain isoprenyltransferase activity in porcine brain: proposed role in the biosynthesis of dolichyl phosphate.

Pig brain microsomes catalyzed the enzymatic transfer of radiolabeled isoprenyl groups from [1-14C]isopentenyl pyrophosphate [( 1-14C]I-P-P) into long-chain polyisoprenyl pyrophosphates (Poly-P-P) and unidentified neutral lipids. The brain isoprenyltransferase activity synthesizing the Poly-P-P (1) required 5 mM Mg2+ and 10 mM vanadate ions for maximal activity; (2) exhibited an apparent Km of 8 microM for I-P-P; (3) utilized exogenous farnesyl pyrophosphate and two stereoisomers of geranylgeranyl pyrophosphate as substrates; (4) was optimal at pH 8.5; and (5) was stimulated by dithiothreitol. The major products were identified as C90 and C95 allylic Poly-P-P on the basis of the following chemical and chromatographic properties: (1) the intact product co-chromatographed with authentic Poly-P-P on silica-gel-impregnated paper; (2) the major product was converted to a compound chromatographically identical to polyisoprenyl monophosphate (Poly-P) by alkaline hydrolysis; (3) treatment of the labeled Poly-P with wheat germ acid phosphatase or mild acid yielded neutral labeled products; (4) the KOH hydrolyzed product coeluted with authentic Poly-P from lipophilic Sephadex LH-20; and (5) the labeled lipids produced by enzymatic dephosphorylation had mobilities identical to fully unsaturated polyisoprenols containing 18 (C90) and 19 (C95) isoprene units when analyzed by reverse-phase chromatography. When subcellular fractions from rat brain gray matter were compared, the highest specific activity was found in the heavy microsomes. These results demonstrate that brain contains an isoprenyltransferase activity, associated with the rough endoplasmic reticulum, capable of synthesizing long-chain Poly-P-P. The enzymatic reactions by which the Poly-P-P intermediate is converted to dolichyl phosphate remain to be elucidated.

Animals↗
PubMed1990

Increased rate of phosphorylation-dephosphorylation of the translational initiation factor eIF-4E correlates with the induction of protein and glycoprotein biosynthesis in activated B lymphocytes.

A 10-50-fold, biphasic increase in the rate of 32Pi labeling of eIF-4E was closely correlated with the induction of protein and glycoprotein biosynthesis when resting murine splenic B lymphocytes (B cells) were activated by bacterial lipopolysaccharide or the combination of phorbol 12-myristate 13-acetate and ionomycin. The fraction of eIF-4E which was phosphorylated only increased from 46% in resting cells to 83% in lipopolysaccharide-activated cells. This discrepancy between the increase in the fraction of phosphorylated eIF-4E and the increase in 32Pi labeling suggested that the phosphoryl group of eIF-4E turns over slowly in resting B cells compared with activated cells. The turnover rate for the eIF-4E phosphate moiety in lipopolysaccharide-activated cells was rapid (t1/2 = 2 h) in comparison to the eIF-4E polypeptide chain, which did not turn over detectably in 6 h. Neither protein kinase C nor a cyclic nucleotide-dependent protein kinase appeared to be involved in eIF-4E phosphorylation in B cells, based on the observations that the metabolic labeling of eIF-4E by 32Pi was insensitive to the protein kinase inhibitors H-7 and HA1004, and that maximal labeling occurred after protein kinase C activity was "down-regulated" to very low levels in phorbol 12-myristate 13-acetate/ionomycin-activated cells. Dephosphorylation in vivo was blocked by okadaic acid (IC50 = 200 nM). These results indicate that a rapid phosphorylation-dephosphorylation of eIF-4E is associated with high translation rates during the activation of B cells, and implicate protein phosphatase-1 (or possibly-2A) in the dephosphorylation of the initiation factor.

Animals↗
PubMed1988

Glycoprotein biosynthesis in B lymphocytes: induction of protein N-glycosylation, RNA synthesis, and DNA synthesis by phorbol ester plus ionomycin is blocked by protein kinase inhibitors.

The combination of phorbol 12-myristate 13-acetate (PMA) and ionomycin produces a dramatic increase in the incorporation of [2-3H]mannose into Glc3Man9GlcNAc2-P-P-dolichol and glycoprotein, and the induction of RNA and DNA synthesis in murine splenic B lymphocytes (B cells). The kinetics of the induction processes and the concentrations of PMA and ionomycin required for the optimal response have been defined. While the levels of induction of RNA and DNA synthesis by PMA + ionomycin were similar to the mitogenic response to bacterial lipopolysaccharide, activation by PMA and the calcium ionophore resulted in a threefold higher stimulation in dolichol-linked oligosaccharide biosynthesis and protein N-glycosylation. These results indicate that all signalling mechanisms that trigger RNA and DNA synthesis may not be sufficient to produce maximal induction of the N-glycosylation apparatus. 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine (H-7), a potent protein kinase C inhibitor, prevented the induction of protein N-glycosylation activity (IC50 = 11 microM), as well as RNA (IC50 = 18 microM) and DNA synthesis (IC50 = 12 microM), two common indices of B cell activation. N-[2-(Methylamino)ethyl]-5-isoquinolinesulfonamide (H-8) also inhibited the induction of oligosaccharide-lipid intermediate, glycoprotein, RNA, and DNA synthesis, but required higher concentrations than H-7 for 50% inhibition. N-(2-Guanidinoethyl)-5-isoquinolinesulfonamide (HA1004), a potent inhibitor of cyclic nucleotide-dependent protein kinases, had little effect on the activation of the B cell metabolic processes. The H-7-sensitive reactions involved in the induction of RNA and DNA synthesis occurred within 4 h, but induction of lipid intermediate and glycoprotein biosynthesis remained sensitive to H-7 for 10 h after exposure to PMA and ionomycin. Direct in vitro assays in the presence of 0.6% Brij 58 reveal that a cytosolic, phospholipid-dependent protein kinase activity is translocated to a membrane site(s) after treatment with PMA and ionomycin, and the translocated protein kinase is sensitive to H-7. The relative order of potency of the protein kinase inhibitors on the metabolic processes strongly supports the hypothesis that protein kinase C, acting synergistically with Ca2+ mobilization, plays a key regulatory role in the early stages of B cell activation. The synthesis of oligosaccharide-lipid intermediates and protein N-glycosylation are also shown to be induced in B cells activated by PMA + ionomycin.

Animals↗
PubMed1988

Chemistry of human erythrocyte polylactosamine glycopeptides (erythroglycans) as related to ABH blood group antigenic determinants.

Human erythrocytes bear carbohydrates linked to both proteins and lipids. The majority of the carbohydrates is carried on two proteins: 1) Band 3 (which carries a high molecular weight polylactosamine, variously termed "Erythroglycan", "poly(glycosyl)peptide" or "lactosaminoglycan" and 2) Glycophorin A (which carries 15 O-linked tetrasaccharides and 1 triantennary N-linked structure). The remainder of carbohydrates are carried mainly by a few other glycoproteins (glycophorins B,C, the glucose transporter and others) with a minor amount carried by glycosphingolipids. This report concerns the Band 3 carbohydrate and its content of potential ABH-active sites. We have determined that an average number of two [Fuc1----2Ga11----4GlcNAc] sequences are carried by each "erythroglycan", polylactosamine N-linked oligosaccharide. One such large oligosaccharide occurs on each molecule of Band 3 polypeptide of which there are 1,000,000 copies per erythrocyte. Therefore, about 2,000,000 possible ABH sites are borne by Band 3 on each erythrocyte. This approximates the number of immunologically estimated ABH sites on human erythrocytes. Thus, Band 3 carbohydrate probably carries the majority of ABH substance on human red cells, while other glycoproteins and glycosphingolipids carry a minor fraction.

ABO Blood-Group System↗
PubMed1987

Inhibitors of protein kinase C block activation of B lymphocytes by bacterial lipopolysaccharide.

Activation of murine splenic B lymphocytes (B cells) by bacterial lipopolysaccharide (LPS) was found to be markedly inhibited by 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7) and N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H-8), two potent inhibitors of protein kinases. The higher sensitivity of DNA synthesis, RNA synthesis and protein N-glycosylation activity to H-7, relative to H-8, strongly supports the proposal that protein kinase C plays a critical role in the activation of B cells. A kinetic study on the time of addition of H-7 indicated that protein kinase C promoted the activation process continuously after the addition of LPS.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1987

Induction of glycoprotein biosynthesis in activated B lymphocytes.

Resting murine splenic B lymphocytes (B cells) can be stimulated to proliferate by exposure to a variety of polyclonal activators. To investigate changes in glycoprotein synthesis that occur during the activation process, N-glycosylation activity was assessed by following the incorporation of [2-3H]mannose into dolichol-linked oligosaccharide intermediates and glycoprotein after B cells were exposed to anti-immunoglobulin M (anti-mu). Stimulation of B cells by anti-mu resulted in a dramatic induction of N-glycosylation activity. The incorporation of radiolabeled mannose into oligosaccharide-lipid increased 9-fold while the rate of labeling of glycoprotein increased 27-fold between 18 and 38 h after exposure to anti-mu. Maximal stimulation of N-glycosylation activity was observed at an anti-mu concentration of 20-50 micrograms/ml. Similar results were obtained when B cells were activated by bacterial lipopolysaccharide (LPS), another polyclonal activating agent. The major dolichol-bound oligosaccharide labeled during the induction period was determined to be Glc3Man9GlcNAc2 by HPLC analysis. Nearly full induction of oligosaccharide-lipid synthesis and protein N-glycosylation was also seen when DNA synthesis was suppressed by activating B cells with anti-mu in a serum-free medium, or by activating with anti-mu or LPS in the presence of hydroxyurea. The results suggest that the N-glycosylation pathway is induced during the G0 to G1 transition or during the G1 period, and that entry into S phase is not required. These studies describe a striking developmental increase in N-glycosylation activity and extend the information on biochemical changes occurring during the activation of B cells.

Animals↗
PubMed1987

A role for ca in the elicitation of rishitin and lubimin accumulation in potato tuber tissue.

Calcium and strontium ions enhanced rishitin but not lubimin accumulation in tuber tissue of potato (Solanum tuberosum cv Kennebec) treated with arachidonic acid (AA). The same cations in the presence of poly-l-lysine (PL) enhanced the accumulation of lubimin more than rishitin. In contrast, Mg(2+) did not affect AA-elicited rishitin and lubimin accumulation and inhibited the accumulation of these compounds following application of PL. AA-elicited potato tuber tissue remained sensitive to the stimulatory effects of Ca(2+) and Sr(2+) up to 24 h after application of AA, but PL-elicited tuber tissue was sensitive to Ca(2+) and Sr(2+) for only 6 hours after PL application. Ethyleneglycol-bis (beta-aminoethyl ether)-N,N'-tetraacetic acid and La(3+) both inhibited rishitin and lubimin accumulation elicited by AA. The inhibition by either agent was overcome by the addition of Ca(2+). Calcium was more effective in overcoming lanthanum inhibition when applied simultaneously than when applied 12 hours later. Lanthanum was only effective in inhibiting rishitin and lubimin accumulation when applied within 3 hours of the application of AA. Inhibition of phytoalexin accumulation was greater when La(3+) was applied simultaneously with AA compared to La(3+) application after AA application to discs. These observations suggest that the mobilization of calcium may play a central regulatory role in the expression of phytoalexin accumulation following elicitation in potato tissue.

Journal Article↗
PubMed1985

Phytoalexins.

Plants respond to infection by accumulating low-molecular-weight antimicrobial stress metabolites called phytoalexins. The phytoalexins are generally lipophilic substances that are products of a plant's secondary metabolism, and they often accumulate at infection sites to concentrations which are inhibitory to the development of fungi and bacteria. Resistance and susceptibility in plants are not determined by the presence or absence of genetic information for resistance mechanisms, including biosynthetic pathways for phytoalexin synthesis, but, rather, by the speed with which the information is expressed, the activity of the gene products, and the magnitude of the resistance response. Unlike the antibody-antigen component of the immune system in animals, low specificity is the general rule for the induction of phytoalexin accumulation and their activity against microorganisms. Annual plants can be systemically immunized against diseases caused by fungi, bacteria, and viruses by restricted infection with the pathogens, avirulent forms of pathogens, or compounds formed in immunized plants. Immunization induces plants to respond rapidly to infection with a multicomponent resistant response. The biosynthesis and accumulation of phytoalexins is one component of this resistant response. Resistance may be elicited by components in the walls and cell surfaces of fungi and bacteria and by compounds liberated from cells, their walls, or surfaces. Resistance can be enhanced or suppressed by products produced by the pathogen, the host, or by their interaction. The successful pathogen avoids recognition by the plant as nonself, suppresses the resistance response, or detoxifies its products. The actors in this play for survival on the metabolic level include the shikimate, acetate-malonate, and acetate-mevalonate pathways; glucans; oligogalacturonates; glycoproteins; lipopolysaccharides; and poly-unsaturated fatty acids. The play is directed by the genetic information of host and pathogen, and this direction is at the level of recognition and not by the presence or absence of mechanisms to contain the development of infectious agents.

Bacteria↗
PubMed1983

A rapid micro-modification of the quantitative immunoprecipitation assay.

A micro-modification of the quantitative immunoprecipitin test is described which permits rapid and sensitive titering of antisera, or quantitation of antigen, within a few hours. The procedure requires less than a microgram of radiolabeled antigen and can be used to titer antisera containing less than 1 microgram/ml of precipitating antibody. Radiotiters obtained for commercial antisera agree closely with results obtained using the classical quantitative immunoprecipitation procedure. The radiotiter assay procedure has been adapted for quantitating albumin in human urine by radioimmunoassay. The analysis can be performed in approximately 1 h, is sensitive to less than 50 ng of albumin, and requires no special apparatus or separation techniques.

Albuminuria↗
PubMed1982

Synthesis of the branched form of erythroglycan by Friend GM979 erythroleukemic cells.

Mouse GM979 erythroleukemic cells were found to synthesize the branched form of erythroglycan, a large polylactosamine structure known to be attached to band 3 and possibly to other proteins on human erythrocytes. Total protein-derived oligosaccharides from GM979 cells, labeled metabolically with [3H]glucosamine, [3H]mannose, or [3H]galactose, were prepared by hydrazinolysis after extracting the lipids. The 3H-labeled oligosaccharides were fractionated on Sephadex G-50 revealing 10-25% of each labeled product as a high molecular weight fraction (Mr = 10,000). Digestion of this [3H]glucosamine fraction with endo-beta-galactosidase from Escherichia freundii, specific for the repeating structure of Gal beta (1 leads to 4)GlcNAc beta (1 leads to 3), resulted in the following four products upon Bio-Gel P-2 Gel filtration: 1) a disaccharide with the structure GlcNAc beta (1 leads to 3)Gal, 2) a trisaccharide with the structure Gal beta (1 leads to 4)GlcNAc beta (1 leads to 3) beta Gal, 3) a tetrasaccharide with the sequence Fuc alpha (1 leads to 2)Gal beta (1 leads to 4)GlcNAc beta (1 leads to 3)Gal, and 4) a large complex fragment which contained mannose, glucosamine, galactose, and fucose (presumably the protein linkage region). Methylation linkage analysis of the large complex fraction shows mainly the presence of 4-substituted and terminal N-acetylglucosamine; 3,6-substituted, 6-substituted, 2-substituted, and 2,3-substituted galactose. The GM979 cell erythroglycan is only 30% susceptible to endo-beta-galactosidase degradation probably because of the branched galactose residues, whereas the linear form of erythroglycan from human K562 cells is 60% susceptible. The branched residues in GM979 cell saccharides indicate that this mouse cell line bears an arborized erythroglycan-like glycopeptide similar to those found on human adult erythrocytes, and thus may be a source for the enzyme which transfers an N-acetylglucosamine residue to a 3-linked galactose to form a 3,6-disubstituted galactose.

Animals↗
PubMed1981

Erythroglycan biosynthesis in K-562 cells. Inhibition of synthesis by tunicamycin and lack of attachment to the G-protein of vesicular-stomatitis virus.

K-562 cells, which express foetal erythroglycan, are shown to synthesize the lipid-linked oligosaccharide intermediates commonly found in tissues and cultured fibroblasts. The addition of tunicamycin, which blocks the formation of these intermediates and thus of asparagine-linked oligosaccharides, inhibits the synthesis of erythroglycan (Mr 7000-11 000). Vesicular-stomatitis-virus infection of K-562 cells results in the glycosylation of the G-protein with the transferrin-type oligosaccharide (Mr 3000), but not with the larger erythroglycan. These results suggest that, in K-562 cells, the early stages of erythroglycan biosynthesis are the same as those of the transferrin-type oligosaccharides. However, maturation of the oligosaccharide is influenced by protein structure such that erythroglycan is only expressed on specific glycoproteins.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1980

Presence of erythroglycan on human K-562 chronic myelogenous leukemia-derived cells.

Total glycopeptides from human K-562 cells, labeled metabolically with [3H]glucosamine or [3H]mannose, were prepared by extracting the cells with organic solvents to remove lipids and by digesting the residue with pronase. 3H-labeled glycopeptides were fractionated on Sephadex G-50 revealing a high molecular weight fraction (Mr = 7,000 to 11,000), comprising approximately 10% of the [3H]glucosamine and 25% of the [3H]mannose label. Digestion of this glycopeptide fraction with endo-beta-galactosidase from Escherichia freundii, specific for a repeating structure of Gal(beta 1 leads to 4)GlcNAc(beta 1 leads to 3), results in the following four products as resolved by Bio-Gel P-2 gel filtration: 1) a disaccharide with the structure beta-2-deoxy-2-acetamidoglucosyl leads to beta-galactose; 2) a trisaccharide with the structure beta-galactosyl leads to beta-2-deoxy-2-acetamidoglucosyl leads to beta-galactose; 3) a tetrasaccharide with the sequence alpha-N-acetylneuraminyl leads to beta-galactosyl leads to beta-2-deoxy-2-acetamidoglucosyl leads to beta-galactose; and 4) a larger, complex fragment which contains mannose and beta-2-deoxy-2-acetamidoglucose and which is probably the protein linkage region. In addition, visualization of radiolabeled glycoproteins by fluorography on polyacrylamide gels revealed a 105,000-dalton "Band 3"-like glycoprotein and other bands that were sensitive to endo-beta-galactosidase. These results indicate that the K-562 cell line bears a glycopeptide, erythroglycan, which has been found on erythrocytes, and that this polymer is expressed mainly in the fetal form as a linear chain.

Anion Exchange Protein 1, Erythrocyte↗