Concanavalin a and Wheat Germ Agglutinin Receptors in the Ascitic Fluid of Rat Hepatomas

The presence of glycopeptide lectin receptors in the ascitic fluid of rats bearing Novikoff or AS-30D hepatoma was investigated. Macrosialoglycopeptides, resistant to pronase digestion, were partially purified from the ascitic fluid of hepatoma-bearing rats by gel filtration on Sephadex G-50. A macrosialoglycopeptide fraction, isolated from the ascitic fluid of rats bearing the Novikoff hepatoma, possessed potent concanavalin A (Con A) receptor activity. This fraction possessed higher Con A receptor activity than did the comparable macrosialoglycopeptide fraction from the ascitic fluid of rats bearing the AS-30D hepatoma; this observation is in agreement with the Con A-induced agglutination properties of these 2 hepatoma cell lines and with the Con A receptor activities of the glycopeptides released from the surface of the hepatoma cells by papain digestion. Rat blood serum contained a comparable macrosialoglycopeptide fraction, which possessed weak Con A receptor activity. The macrosialoglycopeptide fractions from the ascitic fluid of hepatoma-bearing rats possessed wheat germ agglutinin receptor activity. However, this activity was also present in normal rat serum. These results suggest that glycopeptides present on the surface of Novikoff hepatoma cells are shed into the ascitic fluid and may be distinguished from components in normal serum by their Con A receptor activity.

Profiling of concanavalin A-binding glycoproteins in human hepatic stellate cells activated with transforming growth factor-β1

Glycoproteins play important roles in maintaining normal cell functions depending on their glycosylations. Our previous study indicated that the abundance of glycoproteins recognized by concanavalin A (ConA) was increased in human hepatic stellate cells (HSCs) following activation by transforming growth factor-β1 (TGF-β1); however, little is known about the ConA-binding glycoproteins (CBGs) of HSCs. In this study, we employed a targeted glycoproteomics approach using lectin-magnetic particle conjugate-based liquid chromatography-tandem mass spectrometry to compare CBG profiles between LX-2 HSCs with and without activation by TGF-β1, with the aim of discovering novel CBGs and determining their possible roles in activated HSCs. A total of 54 and 77 proteins were identified in the quiescent and activated LX-2 cells, respectively. Of the proteins identified, 14.3% were glycoproteins and 73.3% were novel potential glycoproteins. Molecules involved in protein processing in the endoplasmic reticulum (e.g., calreticulin) and calcium signaling (e.g., 1-phosphatidylinositol-4,5-bisphosphate phosphodiesterase β-2 [PLCB2]) were specifically identified in activated LX-2 cells. Additionally, PLCB2 expression was upregulated in the cytoplasm of the activated LX-2 cells, as well as in the hepatocytes and sinusoidal cells of liver cirrhosis tissues. In conclusion, the results of this study may aid future investigations to find new molecular mechanisms involved in HSC activation and antifibrotic therapeutic targets.

Isolation and identification of Concanavalin A binding glycoproteins from human seminal plasma: a step towards identification of male infertility marker proteins

Human seminal plasma contains a large array of proteins of clinical importance which are essentially needed to maintain the reproductive physiology of spermatozoa and for successful fertilization. Thus, isolation and identification of seminal plasma proteins is of paramount significance for their biophysical characterization and functional analysis in reproductive physiological processes. In this study, we have isolated Concanavalin-A binding glycoproteins from human seminal plasma and subsequently identified them by MALDI-TOF/MS analysis. The major proteins, as identified in this study, are Aminopeptidase N, lactoferrin, prostatic acid phosphatase, zinc-alpha-2-glycoprotein, prostate specific antigen, progestagen-associated endometrial protein, Izumo sperm-egg fusion protein and prolactin inducible protein. This paper also reports preliminary studies to identify altered expression of these proteins in oligospermia and azoospermia in comparison to normospermia. In oligospermia, five proteins were found to be downregulated while in azoospermia, four proteins were downregulated and two proteins were upregulated. Thus, this study is of immense biomedical interest towards identification of potential male infertility marker proteins in seminal plasma.

Cholesterol cholelithiasis in the prairie dog: role of mucin and nonmucin glycoproteins

The aims of this study were to examine the effect of exogenous prostaglandin on mucin secretion and to determine the role of nonmucin glycoproteins on gallstone formation in the prairie dog model of cholesterol cholelithiasis. The concentration of total glycoprotein and nonmucin glycoproteins was measured in gallbladder bile from four groups of prairie dogs fed a control diet or a diet supplemented with 1.2% cholesterol with or without simultaneous subcutaneous administration of prostaglandin E1. Cholesterol feeding resulted in an increased concentration of concanavalin-A binding-proteins in gallbladder bile associated with an increase in pronucleating activity in vitro. Treatment with prostaglandin E1 and cholesterol feeding was associated with a significant increase in the incidence of cholesterol gallstone formation. Prostaglandin E1 treatment in the cholesterol-fed animals increased biliary concentrations of total glycoprotein and concanavalin-A-binding glycoproteins. Therefore the increased biliary glycoprotein level in cholesterol-fed, prostaglandin E1-treated prairie dogs, which reflects higher levels of mucin and nonmucin glycoproteins, appears to be an important factor in gallstone formation.

Isolation of a potent cholesterol nucleation-promoting activity from human gallbladder bile: role in the pathogenesis of gallstone disease

Gallbladder bile contains nucleation-promoting activity that binds to concanavalin A. The activity was found in gallbladder bile from cholesterol gallstone patients but also in gallbladder bile from patients without stones and patients with pigment stones. Bile from patients with multiple cholesterol gallstones contained high concanavalin A-binding nucleation-promoting activity. The activity was much lower in bile samples from pigment stone patients, patients without stones and patients with a solitary cholesterol stone. Serum contained very little activity and no concanavalin A-binding nucleation-promoting activity could be demonstrated in gallbladder mucosa. This suggests that concanavalin A-binding nucleation promoter is produced in the liver or bile duct epithelium. The activity was fully resistant to digestion with pronase but was heat labile and could be destroyed by prolonged incubation with a mixed glycosidase preparation indicating that sugar residues are important for this activity. On a Superose 12 gel permeation column, promoting activity eluted in two major peaks at apparent molecular weights of 150 +/- 30 kD (n = 5) and less than 5 kD respectively. The mobility on the column was not influenced by pronase digestion. The factor with the higher molecular weight could be isolated further by polyacrylamide gel electrophoresis under nondenaturing conditions. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the apparent molecular weight of the glycoprotein was 130 kD. In conclusion, gallbladder bile contains nucleation-promoting activity that binds to concanavalin A. The activity is increased in bile from patients with multiple cholesterol gallstones and could therefore play an important role in the pathogenesis of gallstone disease.

Effects of a concanavalin A-binding biliary glycoprotein on nucleation time of gallbladder bile

A study was performed to determine quantitative differences in the total protein concentration of gallbladder bile from gallstone patients and to isolate nucleation-promoting factors from the bile. Total protein concentrations in cholesterol gallstone bile (3.6 +/- 0.6 mg/ml, mean +/- SD, n = 10), calcium bilirubinate gallstone bile (4.2 +/- 1.1 mg/ml, n = 10), black pigment gallstone bile (1.9 +/- 0.6 mg/ml, n = 4) and control gallbladder bile (2.3 +/- 0.5 mg/ml, n = 9) were not significantly different. Also no statistically significant differences in cholesterol saturation index were found among these groups. Gallbladder bile from cholesterol gallstone patients showed significantly faster nucleation than that of controls, calcium bilirubinate gallstone, or black pigment gallstone patients. We partially purified biliary glycoproteins proteins from cholesterol gallstone bile or calcium bilirubinate gallstone bile by chromatography on concanavalin A Sepharose. Nucleation time was measured following the addition of these proteins to control bile in vitro. The glycoproteins obtained from cholesterol gallstone bile had significant nucleation-promoting activity, but nucleation time was not changed following the addition of biliary glycoproteins from calcium bilirubinate gallstone patients. These results suggest that qualitative differences in individual proteins of gallbladder bile are responsible for nucleation-promoting activity in vitro.

Topography and microfilament core association of a cell surface glycoprotein of ascites tumor cell microvilli

Membrane-microfilament interactions are being investigated in microvilli isolated from 13762 rat mammary ascites tumor cells. These microvilli are covered by a sialomucin complex, composed of the sialomucin ascites sialoglycoprotein-1 (ASGP-1) and the associated concanavalin A (Con A)-binding glycoprotein ASGP-2. Limited proteolysis of the microvilli releases large, highly glycosylated fragments of ASGP-1 from the microvilli and increases the association of ASGP-2 with the Triton-insoluble microvillar microfilament core (Vanderpuye OA, Carraway CAC, Carraway, KL: Exp Cell Res 178:211, 1988). To analyze the topography of ASGP-2 in the membrane and its association with the microfilament core, microvilli were treated with proteinase K for timed intervals and centrifuged. The pelleted microvilli were extracted with Triton X-100 for the preparation of microfilament cores and Triton-soluble proteins or with 0.1 M carbonate, pH 11, for the preparation of microvillar membranes depleted of peripheral membrane proteins. These microvilli fractions were analyzed by dodecyl sulfate gel electrophoresis, lectin blotting with Con A and L-phytohemagglutinin, and immunoblotting with anti-ASGP-2. The earliest major proteolysis product from this procedure was a 70 kDa membrane-bound fragment. At longer times a 60 kDa released fragment, 30-40 kDa Triton-soluble fragments, and 25-30 kDa membrane- and microfilament-associated fragments were observed. Phalloidin shift analysis of microfilament-associated proteins on velocity sedimentation gradients indicated that the 25-30 kDa fragments were strongly associated with the microfilament core. From these studies we propose that ASGP-2 has a site for indirect association with the microfilament core near the membrane on a 15-20 kDa segment.

Binding of plasma membrane glycoproteins to the cytoskeleton during patching and capping is consistent with an entropy-enhancement model

Concentrations of concanavalin A that induced patching and capping of cell surface receptors on Dictyostelium discoideum also induce binding of the receptors to the cortical cytoskeleton, which was isolated by density-gradient centrifugation. The receptors were solubilized by deoxycholate, purified by affinity chromatography, and used to determine whether the receptors bound directly to the cytoskeletal protein, actin. As the concentration of actin was increased, many of the receptors became bound to purified filamentous rabbit muscle actin, even in the absence of concanavalin A. As in the ligation-induced binding of receptors to the cortical cytoskeleton in cells, concanavalin A induced much stronger binding of the purified receptors to filamentous actin. The results were consistent with a previously stated hypothesis that induction of receptor binding to the cytoskeleton during their patching and capping is driven by clustering the receptors, which reduces their translational entropy and by doing so enhances their avidity for the cytoskeleton.

[Identification and characteristics of concanavalin A-binding neurospecific glycoproteins in human brain and brain tumors]

Soluble and membrane-bound neurospecific Con A-binding glycoproteins from human brain and tumours were identified and characterized, using a procedure which included stepwise extraction with low and high ionic strength buffers, buffered. Triton X-100 and sodium deoxycholate followed by ConA-Sepharose column chromatography, SDS-PAAG electrophoresis and immunoblotting. Adsorbed antisera against different types of neurospecific glycoproteins were used. The bulk of neurospecific glycoproteins (11 and 13) were revealed in protein fractions extracted with low ionic strength buffers and Triton X-100. In astrocytomas and glyoblastomas, some neurospecific glycoproteins were absent. Some glycoproteins were found in tumours, but were absent in brain tissue. Soluble, 77 kD glycoprotein, 11 and 16 kD glycoproteins solubilized with high ionic strength buffers and intrinsic membrane-bound 51, 57, 61, 74 and 77 kD glycoproteins can be viewed as stable neurospecific markers in malignant brain tumours.

The major concanavalin A-binding surface glycoprotein of Leishmania donovani chagasi promastigotes is involved in attachment to human macrophages

Leishmania donovani, the protozoan causing visceral leishmaniasis, is an obligate intracellular parasite of mammalian macrophages. Considerable evidence has suggested that the ingestion of L. donovani promastigotes by macrophages occurs via receptors on the surface of the phagocyte. During this study, a glycoconjugate that may be involved in the receptor-mediated ingestion of L. donovani chagasi promastigotes was isolated from the parasite membrane. Octyl glucoside-soluble extracts of promastigote membranes contained a predominant doublet migrating at 60 kDa, seen by SDS-PAGE. The 60-kDa molecule was the major externally disposed promastigote surface protein labeled by 125I, and it was the major Con A-binding protein on L. donovani chagasi, as determined by Con A binding to parasite proteins transferred to nitrocellulose. Attachment of promastigotes to human monocyte-derived macrophages was inhibited by varying concentrations of the membrane extract containing both proteins, and adsorption of extracts on Con A-Sepharose resulted in both removal of the 60,000 Mr glycoprotein and loss of the ability of extracts to inhibit promastigote attachment to human macrophages. After further purification of the 60-kDa glycoprotein by gel filtration, its inhibitory activity increased 45-fold over the unpurified membrane extract. Examination of Con A blots of stationary phase promastigotes isolated from an infected hamster revealed a marked loss in the major Con A-binding glycoprotein over 4 mo in in vitro culture after isolation from the rodent host, corresponding to a loss in infectivity of the promastigotes for hamsters. The results suggest that the major Con A-binding surface glycoprotein from L. donovani chagasi promastigotes is important in attachment to human macrophages, and may be a factor in parasite virulence for a mammalian host.

Studies on the 240-kDa Con A-binding glycoprotein of rat cerebellum, a putative marker of synaptic junctions

A Con A-binding glycoprotein of Mr 240,000 was isolated from the remaining residue of rat cerebella after sequential extraction with buffers supplemented with or without neutral detergents. It was further purified by affinity chromatography on Con A-Sepharose in the presence of sodium dodecyl sulfate and preparative gel electrophoresis. This glycoprotein partially resists Triton X-100 extraction and is soluble in N-lauryl sarcosinate. The 240-kDa glycoprotein was not detected in kidney, liver, heart, forebrain and was specifically seen in cerebellar homogenate. The isolated glycoprotein appears to be similar, not necessarily identical with the GPA--a synaptic junction 240-kDa Con A-binding glycoprotein isolated from cerebellum earlier (Groswald and Kelly, J. Neurochem., 42 (1984) 534-546). Monospecific antibodies obtained against the purified 240-kDa protein were used for developmental study in normal and hypothyroid rats. There was observed an increase in the amount of 240-kDa glycoprotein, dependent on the age of the rat and this rise was in correlation with the synapse formation in rat cerebellum. The amount of 240-kDa glycoprotein is considerably reduced in hypothyroid rats.

Crosslinked concanavalin A-O-(diethylaminoethyl)-cellulose--an affinity medium for concanavalin A-interacting glycoproteins

When concanavalin A (Con A) is reacted with a low concentration of glutaraldehyde, the product formed strongly binds to DEAE-cellulose. Thus, the resultant material can be used as an affinity medium for those glycoproteins which interact with Con A. This affinity medium is easy to prepare, has a capacity comparable to that of similar commercially available affinity media, and is stable for up to at least 6 months.

Plasma membrane proteins from human normal and chronic myeloid leukemic granulocytes: identification and partial characterization of the concanavalin A-binding and detergent resistant proteins

In this work granulocytes from normal human donors and patients suffering from chronic myeloid leukemia (CML) were externally labeled with 125Iodine, using the Iodogen method. 125Iodine labeled Concanavalin A binding proteins (CBP) and detergent-resistant proteins (DRP) were isolated from the cell lysates and characterized by one- and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (1D- and 2D-SDS-PAGE). Autoradiographs of the 2D-gels of DRP show seven proteins with Mr 118,000 (spot 1 a), Mr 112,000 (spot 1b), Mr 78,000-85,000 (spot 2), Mr 85,000 (spot 4), Mr 52,000 (spot 3, 3 a and 3 b). Of this set, spot 1 b, 2 and 4 are also present in the autoradiographs of 2D-gels of CBP and, hence, may be considered to be transmembrane components. Spot 4 is expressed more intensely in the normal granulocytes while spots 3 a and 3 b are mainly expressed on the leukemic granulocytes.

Isolation and initial biochemical characterisation of caps of two major rat thymocyte glycoproteins: evidence for the involvement of a 205 K Con A binding protein and cytoskeletal components in capping

Two major rat thymocyte surface glycoproteins, the leucocyte-common (L-C) antigen and the leucocyte sialoglycoprotein (LSGP), were induced to cap independently, using the specific monoclonal antibodies OX-1 and W3/13, respectively, and an appropriate fluorescently labeled second antibody layer. The caps were subsequently isolated from detergent extracted cells by a procedure involving gentle shearing. TRITC-phalloidin staining of the isolated caps demonstrated the presence of F-actin within these structures, and lectin-affinity staining after fractionation on SDS polyacrylamide gels revealed the presence of a concanavalin A (Con A) binding protein of relative molecular weight (Mr) 205,000, gp205, in both the L-C antigen and LSGP caps, but absent from the detergent-insoluble residue isolated from unchallenged cells. These results suggest that gp205 may be involved in the association of cross-linked glycoproteins with the cytoskeleton during capping.

Specificity of antibodies to the purified Con A acceptor glycoproteins of cultured tumour cells

Con A acceptor glycoproteins from the human Molt 4 (T cell leukaemia) and HeLa (endocervical adenocarcinoma) cell lines were purified by affinity chromatography and used for the preparation of rat antisera. Cross-absorption analysis showed that each antiserum contained antibodies which recognised cell surface antigens preferentially expressed by the donor cell line. Molt 4-associated antigens were fully expressed on T cell tumour lines and normal thymocytes, but not on non T cell tumour lines, peripheral blood lymphocytes or other blood cells. Immunofluorescence studies showed that the antigens were preferentially expressed on a sub-population of immature thymocytes. HeLa-associated antigens were only fully expressed on one other epithelial tumour cell in a panel of 17 cell lines. Immunofluorescence studies showed that the HeLa-associated antigens were expressed on normal endocervical adenoepithelium but not on ectocervical, endometrial or intestinal epithelia. Thus purified Con A acceptor glycoproteins of cultured tumour cell lines are potent immunogens for the generation of antibodies recognising lineage-associated differentiation antigens. These antigens should be useful in tumour classification and in the study of normal differentiation.

Concanavalin A binding glycoproteins in subcellular fractions from the developing rat cerebral cortex

Synaptic plasma membrane (SPM) and mitochondrial fractions were prepared from 3-50-day rat cerebral cortex and their purity assessed. The fractions were subjected to electrophoresis on slab gels, stained for protein, and overlaid with 125I-concanavalin A (ConA). ConA binding glycoproteins (CABGs) were revealed by autoradiography. In the SPM fraction CABGs of MW 25,000, 63,000, 80,000, 115,000, 174,000, and 239,000 increased while those of MW 47,000, 75,000, and 190,000 decreased developmentally. In the mitochondrial fraction, CABGs of MW 25,000, 44,000, 115,000 and 174,000 increased while those of 34,000, 43,000, 47,000, 51,000, 80,000, 107,000, and 195,000 decreased developmentally. CABGs of MW 32,000, 63,000, 88,000, 153,000, 190,000, and 239,000 appear to be unique to the SPM fraction and those of MW 34,000, 107,000, and 195,000 are unique to the mitochondrial fraction.

Isolation and partial characterization of concanavalin A receptors on cloned cytotoxic T lymphocytes

A small set of concanavalin A (Con A)-binding glycoproteins was isolated from the surface membrane of cloned cytotoxic T lymphocytes (CTL) and partly identified using monoclonal antibodies. The binding of Con A by these glycoproteins on the CTL surface results in the secretion of gamma-interferon and in blocking the effector functions of the cells-namely, antigen-specific and lectin-dependent cytotoxicity. The Con A is evidently bound tightly to some surface structures ("Con A-receptors") that are required for the activation and cytotoxic activity of CTL. To isolate and identify these receptors, antibodies to Con A were used. After Con A was allowed to bind to radiolabeled cloned CTL (labeled with 125I or [35S]methionine or 3H-labeled amino acids), the cells were washed thoroughly, lysed in detergents and anti-Con A antibodies were added to bind to the Con A-receptor complexes. The resulting aggregates were adsorbed with protein A-bearing Staphylococci and the receptors were then specifically released from the pelleted bacteria by alpha-methyl-D-mannoside and analyzed by polyacrylamide gel electrophoresis under reducing conditions. Eight to nine labeled components were seen by autoradiography and with the aid of monoclonal antibodies to known T-cell surface molecules, four were identified as T200, lymphocyte function-associated antigen (LFA)-1, alpha- and beta-chains, and (on some clones) Lyt-2. Other components with Mr congruent to 160,000, 120,000, 46,000, 42,000, and 23,000 have not been identified. The procedures described here may have general application in the studies of the functional properties of other cell surface molecules.

Concanavalin A binding glycoprotein in human stratum corneum

A mannose-containing 40K glycoprotein has been identified in the stratum corneum of normal human epidermis. It is apparently membrane-bound and in the intact epidermis it is inaccessible to either concanavalin A or to trypsin. After it is detergent-solubilized, it can be labeled with concanavalin A or destroyed with trypsin. There is little or none of this glycoprotein in the viable cells of the epidermis.

Association of the cyclic AMP chemotaxis receptor with the detergent-insoluble cytoskeleton of Dictyostelium discoideum

Treatment of 6-h differentiated Dictyostelium discoideum cells with the nonionic detergent Triton X-100 dissolves away membranes and soluble components, as judged by marker enzyme distributions, leaving intact a cytoskeletal residue that contains approximately 10% of the cell protein and 50% of the actin. Nitrobenzooxadiazo-phallacidin staining for F-actin and electron microscopy of detergent-extracted whole-mounts indicate that the cytoskeletons retain the size and shape of intact cells and contain F-actin in cortical meshworks. The cytoskeletons contain little if any remaining membrane material by morphological criteria, and the plasma membrane enzymes cyclic nucleotide phosphodiesterase and alkaline phosphatase are absent from the insoluble residue, which retains only 15% of the membrane concanavalin A-binding glycoproteins. This detergent-insoluble residue retains a specific [3H]cAMP-binding site with the nucleotide specificity, rapid kinetics and approximate affinity of the cAMP receptor on intact cells. Upon detergent extraction of cells, the number of cAMP-binding sites increases 20-70%. The binding site is attached to the insoluble residue whether or not the cAMP receptor is occupied at the time of detergent addition. The pH dependence for recovery of the insoluble cAMP-binding site is much sharper than that on intact cells or membranes with an optimum at pH 6.1. Conditions of pH and ionic composition that lead to disruption of the cytoskeleton upon detergent treatment also result in the loss of cAMP binding. During differentiation, the detergent-insoluble cAMP binding increases in parallel with cell surface cAMP receptors and chemotaxis to cAMP.

Identification and localization of concanavalin A binding sites on isolated postsynaptic densities

Synaptic fractions of decreasing morphological complexity were prepared by phase partitioning of synaptic membranes in an aqueous two-phase polymer system containing increasing concentrations of the neutral detergent n-octylglucoside (OG). The morphology, distribution of concanavalin A binding sites (CABS) and protein and glycoprotein composition of the resultant fractions were examined. The lowest concentration of OG employed (0.5% w/w) gave fractions enriched in relatively intact junctions retaining both pre- and postsynaptic structures. Increasing the detergent concentration resulted in the stepwise solubilization of pre- and postsynaptic structures until purified postsynaptic densities (PSDs) were obtained with 1% (w/w) OG. CABS were generally distributed on all membrane structures present in the 0.5% OG fraction, were restricted to synaptic structures in the fraction obtained with 0.75% OG, and were localized to the convex (outer) surface of purified PSDs. Gel electrophoretic analysis showed that the restriction of CABS to the region of the synapse was associated with a marked increase in the concentration of glycoproteins with apparent molecular weights of 180,000 and 130,000. These glycoproteins were retained, and further concentrated in the purified PSD fraction.

Characterization of lectin receptors isolated from the outer acrosomal membrane of boar spermatozoa

The outer acrosomal membrane (OAM) of boar spermatozoa was isolated by homogenization and centrifugation through modified colloidal silica. Homogeneity of the isolated membrane fraction (OAM) was revealed by transmission electron microscopy. At least 10 protein components could be discriminated by SDS-PAGE electrophoresis of the OAM, with molecular weights ranging from 340 to 15 kdal. Radiolabelling of the externally disposed carbohydrate side-chains by [3H]borhydride reduction of the isolated membrane, oxidized by use of galactose oxidase, revealed one main galactoprotein with a reduced molecular weight of about 270 kdal. This was identified as the RCA-120 receptor protein by means of lectin-affinity chromatography, high resolution gelfiltration and SDS-PAGE. Screening of the Con A binding properties of the solubilized membrane components partially isolated by affinity chromatography and HPLC was performed by an enzyme-linked-lectin-assay (ELLA). Electrophoretic analysis including a Con A-peroxidase staining procedure allowed the identification of 4 Con A binding proteins of the OAM with molecular weights of 120, 110, 88 and 66 kdal.

Structure of the mannose-rich oligosaccharide chains of concanavalin A-binding glycopeptides derived from beef brain glycoproteins

A neutral, mannose-rich, concanavalin A (Con A)-binding glycopeptide fraction was obtained by proteolytic digestion of defatted beef brain tissue. Hydrazinolysis followed by gel filtration of the reaction products provided three oligosaccharides. A portion of each oligosaccharide was treated by exhaustive digestion with alpha-mannosidase. Another portion was subjected to selective acetolysis of Man alpha 1 leads to 6Man linkages, providing two fragments that were recovered by gel filtration. The structure of the intact oligosaccharides, as well as the fragments obtained by selective acetolysis and enzymatic treatment, were resolved by gas-liquid chromatographic-mass spectrometric analysis. The structures of the three oligosaccharides were: (a) Man alpha 1 leads to 2Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man alpha 1 leads to 6(Man alpha 1 leads to 2Man alpha 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4-N-acetylglucosamine (GlcNAc)beta 1 leads to 4N-acetylglucosaminitol (GlcOLNAc); (b) Man alpha 1 leads to 2Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man alpha 1 leads to 6(Man alpha 1 leads to 2Man alpha 1 leads to 3)-Man beta 1 leads to 4GlcNAc beta 1 leads to 4GlcOLNAc; and (c) Man alpha 1 leads to 6(Man alpha 1 leads to 3) Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc-beta 1 leads to 4GlcOLNAc. These structures account for 15-20% of the glycoprotein-carbohydrate of whole beef brain and most of the oligosaccharides that demonstrate a high affinity for Con A. In view of the large number of Con A-binding glycoproteins in brain tissue, it appears that many of these different glycoproteins must contain structurally identical oligosaccharides.

Target-effector-cell interactions in the human natural-killer(NK)-system: isolation of target structures

The existence of structures on NK-sensitive target cells selectively recognized by the effector cells have been postulated. To test this hypothesis, four selected human cell lines were investigated for target-cell proteins which could serve as specific ligands for the putative NK-cell receptor(s). NP-40 extracts from two highly NK-sensitive (K 562 and Molt-4) and two rather insensitive cell lines (HL-60 and Reh-6) were fractionated on SDS-polyacrylamide gels and tested for their ability to inhibit binding of effector to target cells as well as NK cytotoxicity. Three fractions with molecular weights (MW) of 200, 120 and 80 +/- 10 KD isolated from K 562 cells were able to inhibit binding of large granular lymphocytes (LGL) to K 562. Of the other cell lines, Molt-4 and HL-60, both which were able to inhibit lysis of K 562 in a cold target inhibition assay, showed also two inhibitory fractions with MW 120 and 80 KD, whereas Reh-6, which is not able to compete with 51Cr-labelled K 562 in a cytotoxicity assay, lacked these structures. The 200, 120 and 80 KD fractions isolated from K 562 and the 120 and 80 KD fractions from Molt-4 and HL-60 were able to inhibit lysis of K 562 cells when added to the cytotoxicity assay. By adsorption/elution of radiolabelled K 562 extracts to/from LGL it was possible to detect an 80 KD target-cell surface protein which became preferentially bound by LGL-enriched but not by LGL-depleted lymphocyte preparations. Our results indicate the existence of target-cell proteins in NK-sensitive cell lines which serve as specific ligands for binding of NK cells. These target-cell structures of human cell lines differed from NK target structures described for mouse-NK-sensitive cell lines.

Characterisation of Concanavalin A-binding glycoproteins from mouse splenic leukocytes by two-dimensional electrophoresis: preferential binding of incompletely glycosylated forms of H-2 antigen to the lectin

Concanavalin A (Con A)section-binding proteins from mouse spleen leukocytes were characterised by two-dimensional electrophoresis of material precipitated, by Con A plus anti-Con A, from lysates of biosynthetically-labelled cells. Although most cell surface (iodinatable) proteins are known to bind Con A, some of the major Con A-binding proteins detected by immunoprecipitation, after a four-hour biosynthetic labelling period, are not iodinatable and are probably intracellular. Thus the major biosynthetically labelled Con A-binding species are: (i) a non-iodinatable, high molecular weight glycoprotein (C-145); (ii) intracellular precursors of secretory immunoglobulins (IgM and, probably, IgA); (iii) immature (not fully-sialylated) forms of H-2 D and K antigens; and (iv) Ia antigens. In the case of the H-2 antigens, (and possibly of other cell surface proteins) the selection of immature forms by Con A is not due to lack of biosynthetic labelling of mature products, but to preferential binding of Con A to incompletely glycosylated molecules.

Binding of concanavalin A to calf brain synaptic vesicles

Concanavalin A was employed as a tool to investigate the organization of synaptic vesicle glycoproteins. The lectin was incubated in the presence of both intact and Triton X-100 treated calf brain synaptic vesicles. Electrophoresis of treated membranes clearly demonstrated that the majority of Concanavalin A binding sites was not exposed in intact synaptic vesicles. The vesicles were isolated by the procedure of DeLorenzo and Freedman (DeLorenzo, R. J., and Freedman, S. D. (1978) Biochem. Biophys. Res. Commun. 80, 183-192). However, an extra centrifugation step at 55,000 g was required to obtain plain vesicles nearly free from coated vesicles and membrane fragments.

Concanavalin A receptors associated with rat brain synaptic junctions are high mannose-type oligosaccharides

Glycoproteins were isolated from a rat brain synaptic junction fraction by affinity chromatography on Concanavalin A-agarose. The isolated glycoproteins were digested with pronase and radiolabeled with 125I-Bolton Hunter reagent, and 125I-Concanavalin A-binding glycopeptides were isolated by chromatography on Concanavalin A-agarose. Treatment of the 125I-Concanavalin A-binding glycopeptides with either alpha-mannosidase or endo-beta-N-acetylglucosaminidase-C11 abolished their interaction with Concanavalin A. The pronase digest was reacted with endo-beta-N-acetylglucosaminidase-C11 and released oligosaccharides were reduced with NaB3H4. Following affinity chromatography on Concanavalin A-agarose, Concanavalin A-binding [3H]oligosaccharides were chromatographed on Biogel P4. Two major oligosaccharides corresponding to standard carbohydrates containing eight and five mannose residues were identified. Treatment of these oligosaccharides with alpha-mannosidase converted them to smaller saccharides having a mobility on Biogel P4 columns equal to the standard disaccharide mannose-beta-1-4-N'-acetylglucosamine. These results demonstrate that the Concanavalin A receptor activity associated with CNS synaptic junctions resides in asparagine-linked oligosaccharides of the high-mannose type.

Partial structural analysis of concanavalin A binding glycopeptides of large size from human teratocarcinoma-derived cells: cleavage by hydrazinolysis and alkaline borohydride

Pronase digests of cultured teratocarcinoma-derived cells (PA 1) of human origin have been previously shown to contain large-sized glycopeptides (relative mass (Mr) greater then 7400), of which 15-23% are retained by columns of concanavalin A (Con A) - Sepharose and can be eluted with 10 mM methyl alpha-D-mannopyranoside. The present data show that this fraction (A - Con A II) contains a family of glycopeptides that are degradable with anhydrous hydrazine as well as with 0.05 M NaOH - 1 M NaBH4. The cleavage products representing individual oligosaccharide chains, presumably as oligosaccharides and glycopeptides, consisted mostly of medium- (Mr 1400-6000) and small-sized (Mr less than 1400) molecules. This implies that glycopeptides bearing several oligosaccharide chains were present in A - Con A II. Most of the individual oligosaccharide chains were not bound to Con A - Sepharose, but some were retained by the lectin column in the same way as the original glycopeptides. Some of the oligosaccharides were degraded partially with endo-beta-galactosidase from Escherichia freundii suggesting the presence of GalbetaGlcNAcbeta repeats. The present findings show that A - Con A II may be different from the "embryonic" glycopeptides of mouse teratocarcinoma cells that are reportedly not cleaved by mild alkaline borohydride treatment. Instead, A - Con A II is reminiscent of the T-1 glycopeptide of glycophorin.

Purification and characterization of a major cell surface glycoprotein in Zajdela ascites hepatoma cells which displays a potent concanavalin A receptor activity

A major cell surface sialoglycoprotein with Concanavalin A receptor activity has been isolated from rat Zajdela ascites hepatoma cells. The sialic acid residues of the plasma membrane glycoproteins were specifically labeled by oxidation and NaIO4 followed by reduction with NaB3H4. Surface-labeled glycoproteins were released by short incubations with TPCK-trypsin at 37 degrees C and then separated by gel filtration on Sepharose 6B column. The predominantly labeled fraction, GP II2, was then purified by chromatography on DEAE-cellulose equilibrated with 0.05 M phosphate buffer, pH 7.5, and eluted with increasing molarities of NaCl. It was shown to be homogeneous by protein and carbohydrate staining on SDS-polyacrylamide gels, isoelectric focusing, rechromatography on DEAE-cellulose and immunoelectrophoresis. It has an apparent molecular weight of 110,000 daltons. The location of GP II2 on the cell surface was confirmed by the fact that it could be labeled metabolically with D-(3H) glucosamine and externally through the nonpenetrating periodate-NaB3H4 system. GP II2 could not be removed from the cell surface by high salt concentrations, chelator, or chaotropic agents but was released from the membrane by detergents. This suggests that GP II2 could be an integral protein. Analysis of the carbohydrate composition of GP II2 revealed galactose, N-acetylglucosamine, N-acetylgalactosamine, and sialic acid as major constituents and mannose as a minor one. This suggests that it contains carbohydrate chains both O- and N-linked to the polypeptide chain, most of them being O-linked. Finally, GP II2 has a potent Concanavalin A receptor activity. It inhibits the interaction between Concanavalin A and hepatoma cells and suppresses its effects on hepatoma cell proliferation.

The isolation and characterization of a concanavalin A receptor from boar spermatozoa surface

Boar spermatozoa were radioactively labeled by either lactoperoxidase-catalysed iodination or galactose oxidase oxidation followed by reduction with tritiated sodium borohydride. Plasma membrane glycoproteins were solubilized with the non-ionic detergent Nonidet P40 and separated by affinity chromatography on concanavalin A-Sepharose. A major water-soluble concanavalin A receptor of molecular weight greater than 160 000 was isolated by gel filtration and ion-exchange chromatography. Its amino acid and carbohydrate composition were determined. This glycoprotein is susceptible to digestion by trypsin or chymotrypsin.

Transient concanavalin A-binding glycoproteins of the parallel fibres of the developing rat cerebellum: evidence for the destruction of their glycans

The lifetime of the glycoprotein glycans of the rat cerebellum was followed in the 2nd and 3rd weeks of postnatal age, after injection of labelled glucosamine. It appears that a particular class of glycans binding to Concanavalin A synthesized at an early age has a short lifetime. These results indicate that the glycans of the concanavalin A-binding glycoproteins abundant on the newly formed parallel fibres are rapidly degraded between the 14th and the 18th postnatal day.

Subcellular distribution and partial characterization of the three major classes of concanavalin A receptors associated with rat brain synaptic junctions

Synaptic junctional complexes from rat brain contain three major classes of glycoproteins which react with concanavalin A. They have apparent molecular weights of 110,000 (GP 110) 130,000 (GP 130), and 180,000 (GP 180). They are present in postsynaptic densities but are not found in microsomes, axolemma, synaptic vesicles, or myelin and are present in low concentrations in the Triton X-100 extract obtained during the preparation of synaptic junctions suggesting that they are uniquely localized to the postsynaptic apparatus. Reaction of the individual glycoproteins, partially purified by affinity chromatography on concanavalin A-agarose followed by polyacrylamide gel electrophoresis, showed that GP 130 contained the most receptor sites for concanavalin A per unit of protein followed by GP 180 and GP 110. Of the receptor sites for concanavalin A, 60-70% were subject to hydrolysis by endoglycosidase H indicating that the lectin reacts primarily with polymannose asparagine linked oligosaccharides. Each of the glycoproteins also reacted to varying degrees with the lectins from Lotus tetragonolobus (specific for alpha-L-fucose), wheat germ (N'-acetyl-D-glucosamine and (or) sialic acid), and lentils (mannose, N'-acetyl-D-glucosamine). Chromatography of 125I-labelled concanavalin A positive glycoproteins on wheat germ Sepharose resolved GP 110 and GP 180 into wheat germ positive and negative components indicating the presence of some structural heterogeneity within these molecular weight classes.

Concanavalin A surface receptors and cytoplasmic actin in cell adhesion

A double immunofluorescence staining technique to locate concanavalin A (Con A) surface receptors and cytoplasmic actin in the same cell was applied to monolayer cultures of rat foetal fibroblasts during cell detachment induced by trypsin and during cell attachment to glass substratum. Con A receptors were demonstrated by fluorescein-isothiocyanate-labelled Con A (FITC-Con A) and actin by specific anti-actin antibody (AAA) traced with rhodamine-labelled goat anti-human globulin (R-AHG). Untreated, control cells had an elongated shape, Con A receptors restricted to cell margins and prominent actin filaments. After 2 min treatment with 0.001% trypsin the cells became angular with Con A receptors in clusters and actin in a diffuse or aggreagate staining pattern. Progressive cell rounding followed and this was accompanied by the development of long, thin, arborized cell processes, studded with Con A receptors and containing fine actin filaments. Complete cell rounding preceded cell detachment. The sites of detached cells were marked by fine aggregates containing Con A receptors and actin. In cells attaching to a glass substratum, actin was present in a diffusely stained or aggregate pattern in round cells, in filaments restricted to cell margins in partially spread cells and in numerous filaments in fully spread cells. Con A receptors were present in clusters in round cells, in clusters or caps in partially spread cells and in cell margins in fully spread cells. Binding of FITC-Con A to partially spread cells resulted in dissolution of the few, newly formed, actin filaments. We believe our observations are consistent with the idea that actin filaments, formed during cell attachment, contribute towards the maintenance of cell adhesion by helping in the preservation of cell shape and by anchorage of Con A receptors at points of cell attachment to the substratum.

Isolation of concanavalin A caps during various stages of formation and their association with actin and myosin

Regions of plasma membrane of dictyostelium discoideum amoebae that contain concanavalin A (Con A)-receptor complexes are more resistant to disruption by Triton X-100. This resistance makes possible the isolation of Con A-associated membrane fragments in sufficient quantity and homogeneity to permit the direct biochemical and ultrastructural study of receptor-cytoskeletal interactions across the cell membrane. After specific binding of Con A to the cell surface, a large amount of the cell's actin and myosin copurifies with the plasma membrane fragments. Myosin is more loosely bound to the isolated membranes that actin and is efficiently removed by treating membranes with ATP and low ionic strength. If cells are not lysed immediately after lectin binding, all of the Con A that is bound to the cell surface is swept into a cap in a process requiring metabolic energy. When cells are lysed at different stages of cap formation, the amount of actin and myosin that copurifies with the isolated membranes remains the same. Thick and thin filaments that are attached to the protoplasmic surface of the isolated membranes underlie lectin-receptor complexes during all stages of cap formation. Once the cap is complete, the amount of actin and myosin that tightly bound to the plasma membrane is concentrated into the cap along with the Con A-receptor complexes. These results suggest that the ATP-dependent sliding of membrane-associated actin and myosin filaments is responsible for the accumulation of Con A-receptor complexes into a cap on the cell surface.

Concanavalin A receptors in normal and inflamed oesophageal epithelium. A light and electron microscopic study

We have examined normal and inflamed oesophageal biopsies for the distribution of alpha-D-mannosyl and alpha-D-glucosyl residues using the concanavalin A--horse radish peroxidase--Diamino-benzidine (DAB) technique at the light and electron microscope level. Receptors were found on the epithelial surface and in the nuclear membrane and endoplasmic reticulum. A similar distribution was found with the intrusive lymphocytes and polymorphonuclear leucocytes in the inflamed state. Some of the increased intercellular debris from inflamed biopsies contained concanavalin A receptors.

Reconstitution of the erythrocyte anion channel

Band 3, the membrane protein which mediates erythrocyte anion exchange, was purified on a concanavalin A column. Triglycerides, diglycerides, cholesteryl esters, cholesterol, and phosphatidylcholine were found to copurify. The column product gave at least two and probably three bands by isoelectric focusing. Antibodies prepared against the purified Band 3 appeared to react only with the cytoplasmic face of Band 3. Vesicles prepared with Band 3 had an accelerated uptake of SO4(2-) which could be inhibited by 2-(j'-aminophenyl)-6-methyl benzene thiazo-3', 7-disulfonic acid, a potent inhibitor of anion transport in the intact system. The possible source of this difference is discussed. Band 3 was spin labeled, probably at one specific site. The spectra showed that the spin label was highly immobilized, but no dipole-dipole interactions between spin labels on adjacent Band 3 subunits were apparent.

[Isolation and partial characterization of receptor sites of normal human lymphocytes for lectins]

Glycoproteins of the lymphocyte surface are involved in many membrane mediated events. Their specific carbohydrate determinants might interact with lectins. Purification of macromolecules released from normal human lymphocytes by trypsin was performed using gel filtration and affinity properties for Ricinus sanguineus agglutinin. Some structural and biochemical characteristics are given. Relation to HLA determinants and surface immunoglobulins is discussed.

Nephritogenoside, the receptor glycoprotein for concanavalin A in rat glomerular basement membrane. Demonstration of alpha-D-glucopyranosyl unit at the non-reducing terminus

Rat glomerular basement membrane was extracted for 3 h with trypsin, pH 8.0. The supernatant solution was treated with trichloroacetic acid and the supernatant thus obtained was applied to Bio-Gel P200. The first of the two glycoprotein peaks was applied onto Sepharose derivatives of concanavalin A (Con A). Examination of the material retained by the unsolubilized Con A and subsequently eluted with methyl alpha-D-mannopyranoside reveals that the principal high affinity receptor for Con A is the renal glycoprotein, having antigenic activity that induces nephrotoxic antibody. This glycoprotein has also nephritogenicity (the activity capable of inducing glomerulonephritis in homologous animals by a single foot pad injection with Freund's incomplete adjuvant). Evidence is given to show that this binding is specific. The remainder of the renal glycoprotein is unretarded and is revealed to contain none of the activities described above. When fluorescein isothiocyanate-labelled Con A is, conversely, injected into rats through the renal artery, the specific binding of Con A to the glomerular capillary loop is proved. The results demonstrated appear to, indicate that the receptor for Con A present in normal rat glomerular basement membrane can be identified as the well-established chemical substance, the nephritogenoside, having the alpha-D-glucopyranosyl unit at the non-reducing terminus which is facing the endothelial aspects of the glomerular capillary loop.

Lectins as probes of chromatin structure. Binding of concanavalin A to purified rat liver chromatin

Concanavalin A (Con A) binds specifically to rat liver chromatin. The extent of binding is directly proportional to both chromatin and concanavalin A concentration. It is reversible and inhibited by specific sugars for which concanavalin A has a binding site. Scatchard analysis reveals the presence of one type of Con A-binding site, with an apparent dissociation constant of 3 X 10(-7) M. A maximum of 10 pmol of Con A binds to 10 microgram of chromatin, indicating an average of one binding site/1400 base pairs of DNA. To identify the polypeptide chains which contain Con A-binding sites, chromosomal proteins were separated by electrophoresis on polyacrylamide gels containing sodium dodecyl sulfate. Con A receptors were localized by incubating the gel in 125I-Con A and subsequent autoradiography. Three major polypeptide bands which bind Con A were identified among the nonhistone chromosomal proteins. The apparent molecular weights of these glycoproteins are 135,000, 125,000, and 69,000. We suggest that lectins may serve as probes for the study of the organization of specific components in chromatin.

Control of density and microredistribution of concanavalin-A receptors in rat thymocytes at 4 degrees C

In a previous paper, we reported that at 4 degrees C, a cooperative binding of concanavalin A to rat thymocytes is observed which corresponds to a modification of the membrane leading to the recruitment of receptors and their immobilization. In this paper, we report that both phenomena are modulated at 4 degrees C by drugs such as colchicine and cytochalasin B; cooperative binding of concanavalin A, which reflects receptor recruitment is only slightly modified by each drug alone. when the two drugs are used simultaneously, the binding of concanavalin A to rat thymocytes at low concentrations of the lectin is decreased, while at high concentrations it remains unchanged. The binding of succinyl-concanavalin A to drug-treated cells is lowered at all concentrations of lectin. Also, we have studied the effects of colchicine and cytochalacine B on the binding of horseradish peroxidase to cell-bound concanavalin A, or succinyl-concanavalin A. We have found a decreased amount of horseradish peroxidase binding to concanavalin A bound to cells treated with colchicine or cytochalasine B. In the presence of the two drugs the decrease of peroxidase binding suggested a synergistic action of colchicine and cytochalasin B.

Characterization and isolation of concanavalin A binding sites from the epidermis of S. mansoni

Using concanavalin A labeled with tritium and fluorescein isothiocyanate we studied the binding properties of this plant lectin to adult paired schistosomes. Using concanavalin A coupled to a sepharose column we attempted to isolate and characterize concanavalin A binding molecules from the epidermis of adult schistosomes. Our results indicate the presence of specific concanavalin A binding sites on the surface of adult Schistosoma mansoni. A significant percentage of the concanavalin A was specifically bound and showed characteristics similar to that identical in other concanavalin A binding tissues. The parasite's concanavalin A binding sites appear to be 2 or 3 high molecular weight glycoproteins. There is some indication that glycoproteins associated with the worm's epidermis function as enzyme(s). The immunological significance of these glycoproteins has not been determined.

A novel approach to the identification of surface receptors. The use of photosensitive hetero-bifunctional cross-linking reagent

Methyl 4-azidobenzoimidate, a photosensitive hetero-bifunctional cross-linking reagent, was synthesized and characterized. This reagent has an imidoester at one end, which reacts spontaneously with primary amines, and an arylazide at the other end, which reacts with a variety of chemical groups upon photolysis by ultraviolet radiation. The reagent molecules were attached to concanavalin A by reactions between imidoester groups of the reagents and free amino groups of the lectin. These activated lectins were purified on a Sephadex G-25 column and showed the binding affinity to an affinity column, glucosylated Sepharose, and to the human erythrocyte ghost membrane. The activated lectins were incubated with the membranes and then unbound lectins were removed by washing. The lectins bound to receptors in the membranes were irradiated with a shortwave ultraviolet lamp to photolyze arylazides attached to the lectins, thus cross-linking the lectins and receptors together. Then the membranes were solubilized and electrophoresed. On gels, the intensity of the lectin receptor band diminished slightly and concomitantly a new band of a higher molecular weight appeared. When 125I-labeled concanavalin A was used, the new band contained the radioactivity. The extent of the appearance of the new band and the decrease of the receptor band were reduced significantly when the ultraviolet irradiation was omitted or the activated lectins were incubated with the membranes in the presence of the lectin inhibitor, alpha-methylmannoside. The irradiation of nonactivated, receptor-bound concanavalin A did not cause those changes. When the activated lectins alone were irradiated with ultraviolet, the band of the lectin dimer appeared whereas nonirradiated lectins appeared mostly as monomers. It is concluded that a small fraction of the activated lectins were cross-linked to receptors in the membrane upon photolysis. In this study, only 8 reagent molecules were attached to a tetramer of the lectin, compared with the presence of approximately 40 available free amino groups. The efficiency of such cross-links of ligands to receptors may be increased by employing longer versions of the hetero-bifunctional cross-linking reagents and also by attaching more of the reagent molecule to ligands.