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S Kuchler

Publications and source records attributed to S Kuchler.

At least 19 recordsLinked to original sources
PubMed1994

Mannose dependent tightening of the rat ependymal cell barrier. In vivo and in vitro study using neoglycoproteins.

The possible role of carbohydrate binding proteins (lectins) and glycoconjugates in the formation of junctions ensuring tightening between ependymal cells was studied using synthetic glycoconjugates, the neoglycoproteins. These compounds are prepared by substituting bovine serum albumin with sugar residues and additional labelling (or not) with fluorescein or biotin. Injections of these components into the cerebral ventricles of adult rats resulted in a binding pattern which could be related to their carbohydrate composition. Mannose-containing neoglycoproteins were bound to ependymal cell cilia and penetrated rapidly the brain tissue. Such phenomenon was not seen with glucose- or galactose-containing neoglycoprotein molecules. In contrast, mannose-, galactose- and glucose-containing neoglycoproteins bound strongly to some endothelial cells around blood vessels. Fluorescent unglycosylated serum albumin did not bind to any brain structures. In contrast, co-injection of mannose-containing non-fluorescent neoglycoproteins with the other fluorescent compounds (including fluorescent sugar-free BSA) resulted in the penetration of the fluorescent compounds into the brain tissue. This internalization into brain was attributed to disaggregation of junctions between ependymal cells. Cultured ependymal cells behaved likewise. In short term experiments (5 min-1 h), only the mannose-containing neoglycoproteins bound strongly to the ependymal cells, particularly to the cilia. In long term experiments (1-9 days), mannose-containing neoglycoproteins specifically induced the disappearance of junctions between the cultured cells. These results emphasize the importance of mannose-dependent recognition system in the maintenance of junctions between ependymal cells, where a mannose-binding lectin has been previously detected.

Animals↗
PubMed1994

Differential expression of an endogenous mannose-binding protein R1 during muscle development and regeneration delineating its role in myoblast fusion.

The role of the endogenous brain carbohydrate-binding protein R1 in muscle cell development and regeneration was analysed both in vivo and in vitro. In vivo, R1 was developmentally regulated, with an embryonic 65,00 subunit and a neonatal 67,000 subunit, being replaced progressively by a 135,000 adult form. Lectin R1 was intracellularly localized at birth and in the prenatal period. During development and at the time of myoblast fusion, the antigen was progressively found at the surface, where it remained at low levels in the adult. In vitro, in pure myoblast cultures, only the embryonic form was present. The ultrastructural studies indicated that the lectin could participate in the membrane fusion process during myoblast fusion. The specific role in myoblast fusion, derived from the ultrastructural localization of R1, was evidenced by a strong inhibitory effect of anti-R1 Fab fragments (10-100 micrograms/ml), relative to control Fab fragments. In vivo, the embryonic subunit pattern and subcellular distribution of R1 reappeared in muscle cells after lesion of the adult muscle. This suggested that, as observed in vitro, R1 participated in vivo in the phenomenon of myoblast fusion. Similar modifications in subunit expression were observed in muscles after denervation (the embryonic form of lectin R1 reappearing after lesion), suggesting that R1 could be involved in the process of neuromuscular junction formation. Thus, it is proposed that the carbohydrate-binding protein R1 is an important recognition molecule for the formation of myotubes. Its potential involvement in a recognition process between axons and muscle cells during neuromuscular junction formation is discussed.

Animals↗
PubMed1994

Carbohydrates and soluble lectins in the regulation of cell adhesion and proliferation.

There is a large body of suggestions that complex carbohydrates play a role in the regulation of cell adhesion and cell proliferation. Many reports have emphasized that proteoglycans, glycoproteins or glycolipids are participating to cell adhesion mechanisms. The use of polyvalent anti-carbohydrate antibodies and plant lectins as well as the use of glycosylation inhibitors suggested that cell proliferation can be modulated by surface carbohydrates. The dating experiment of Burger and Noonan (1970) showing restoration of contact inhibition of malignant cells by monovalent concanavalin A was a determining experiment. However, in the latter as in the others, no precise mechanism was demonstrated how carbohydrates can be involved in adhesion and proliferation. New insights were opened with the discovery of vertebrate membrane-bound and soluble lectins. The latter generally display agglutinating activities in in vitro systems, suggesting that they were potential cell adhesion molecules, by forming bridges between cell surface carbohydrates. These polyvalent molecules may be also considered as clustering agents for their cell surface ligands, consequently generating signals for cell proliferation and/or differentiation.

Animals↗
PubMed1993

Cerebellar soluble lectin and its glycoprotein ligands in the developing brain of control and dysmyelinating mutant mice.

The levels of an endogenous lectin, the cerebellar soluble lectin (CSL) and of its endogenous glycoprotein ligands were studied using immunoblotting and affinoblotting techniques in the forebrain of quaking, shiverer and jimpy dysmyelinating mutant mice and their respective control littermates during the postnatal development. In the controls of the mutant mice, the level of CSL showed an important increase between days 5-18 then a stabilization, although at all ages the level of CSL was reduced (at least 15%) in the control littermate of the shiverer mutant. In the shiverer mutant the developmental pattern is similar to the control but was reduced by 50% as compared to the control. In the jimpy mutant an erratic development of CSL was observed which was with quasi absence of CSL at days 12 and 25. Variation of CSL levels in the quaking brain were also observed. CSL glycoprotein ligands also showed variable developmental profiles with a special persistence with ageing of CSL-binding glycoproteins in the quaking and jimpy mice. Developmental variations were also observed between the different control littermates. These results are discussed in view of developmental roles attributed to CSL and its glycoproteins ligands in cell adhesion mechanism during brain ontogenesis and especially myelination.

Aging↗
PubMed1993

Lesion-induced re-expression of neonatal recognition molecules in adult rat cerebellum.

It has been previously shown that sectioning of parallel fibers in the cerebellar molecular layer of adult rats gave rise to rapid reinnervation of the target cells, i.e., Purkinje cells. This paper reports that such a reinnervation is accompanied by reexpression (partial and total) of two developmentally regulated complementary molecules. These are an endogenous mannose-binding lectin, called R1, which reappears at the surface of the dendrites of Purkinje cells, and an endogenous glycoprotein ligand of R1, the 31 kDa glycoprotein, which seems to be neosynthetized and transported to the surface of parallel fibers. In this system, embryonic N-CAM is not reexpressed in neurons but reappears in reactive astrocytes in the vicinity of the lesion. The reexpression of recognition molecules (lectin and glycoprotein ligand) involved in normal synaptogenesis, may constitute the molecular basis for repair of nervous circuits in the adult as well.

Animals↗
PubMed1993

Malignant cells have increased levels of common glycoprotein ligands of the endogenous cerebellar soluble lectin CSL.

The glycoprotein composition of various transformed cells or malignant tumors was analyzed and compared to their respective non-malignant control cells or tissues of several species, including man, using an endogenous carbohydrate-binding protein, the cerebellar soluble lectin CSL (Zanetta et al., J. Neurochem. 49, 1250-1257 (1987). A large variety of transformed cells contain a much higher number and larger quantity of glycoprotein ligands of CSL than the control cells or normal tissues. The glycoprotein profiles were, in most cases, independent of the nature of the cell transformation of the degree of differentiation, of the tissue and species. Thus, it is suggested that many transformed cells have, as a common anomaly, the increased synthesis of the special type of glycan recognized by CSL, expressed on the same polypeptide chains.

Animals↗
PubMed1992

Glycoproteins and lectins in cell adhesion and cell recognition processes.

The discovery of endogenous lectins having specific and high affinity for the carbohydrate portions of glycoproteins has opened up new directions in the field of cell adhesion and cell recognition. Two endogenous lectins, termed as CSL and R1, initially isolated from the rat cerebellum and having a wide distribution in mammalian tissues, have been shown to participate in essential mechanisms of cell adhesion. The membrane-bound lectin R1 seems to be involved in transient recognition between neuronal cells, followed by elimination of the glycoprotein ligands at the surface of the recognized cell. In contrast, CSL is a molecule involved in adhesion between various normal or transformed cells since it participates in the formation of tight junctions. The glycoprotein ligands recognized with higher affinity by these two lectins seem to possess a special structure which defines a sub-class of oncofetal HNK-1 glycans. The over-expression of the glycoprotein ligands of these lectins in most transformed cells provides new tools for understanding the underlying mechanism of malignant transformation as well as the generation of signals through cell adhesion.

Animals↗
PubMed1992

Endogenous lectin cerebellar soluble lectin involved in myelination is absent from nonmyelinating Schwann cells.

In the sciatic nerve, two major classes of Schwann cells are present which differ in their capability to produce myelin. Myelinating Schwann cells surround most of the axons with the formation of a typical myelin sheath. Nonmyelinating Schwann cells serve to insulate individual axons without formation of myelin. These dissimilarities between the two types of Schwann cells provided an interesting model for studying mechanisms underlying myelination and the formation of contacts between axons and myelinating cells. It is demonstrated here that the endogenous lectin cerebellar soluble lectin (CSL), implicated in myelin stabilization and in formation of contact between axon and myelinating cells in the CNS and in the sciatic nerve, is undetectable in non-myelinating Schwann cells. In contrast, most axons surrounded by these cells contained the major axonal glycoprotein ligand of CSL, a 31-kDa glycoprotein which is present in large amounts. The possible relationship between the presence of CSL in Schwann cells and their capacity to interact with axons and to produce myelin are discussed.

Animals↗
PubMed1992

Carbohydrate moieties of myelin-associated glycoprotein, major glycoprotein of the peripheral nervous system myelin and other myelin glycoproteins potentially involved in cell adhesion.

The myelin-associated glycoprotein (MAG) and the major glycoprotein of the peripheral nervous system myelin (P0) are two members of the family of cell adhesion molecules (CAMs). A role in cell adhesion of the carbohydrate moiety of these molecules has been attributed to the presence of N-glycans bearing the HNK-1 carbohydrate epitope. On the other hand, it has been suggested that these glycoproteins could be ligands of an endogenous mannose-binding lectin present in myelin, the cerebellar soluble lectin (CSL). In order to further document the heterogeneity of the glycans of these two CAMs, we have used several probes: an anti-carbohydrate antibody of the HNK-1 type, called Elec-39, the plant lectin concanavalin A (ConA), and the endogenous lectin CSL involved in myelin compaction. This study shows that CSL binds to a small proportion of the polypeptide chains of MAG found in adult CNS of rats and man and the polypeptide chains of P0 molecules from adult human and rat sciatic nerve. For MAG from adult rat brain, the binding of CSL is restricted to glycans of polypeptide chains which could be separated from the others according to their solubility properties. These MAG molecular entities react also with the Elec-39 antibody and with ConA. These results confirm that P0 and MAG are heterogeneous in their carbohydrate moieties.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Detection of binding sites for biotinylated neoglycoproteins and heparin (endogenous lectins) during cerebellar ontogenesis in the rat: an ultrastructural study.

In a previous paper (Kuchler et al., Eur. J. Cell Biol. 52, 87-97 (1990)), endogenous carbohydrate-binding sites were studied at the optical level during rat cerebellar development on sections of fixed tissue using synthetic tools, biotinylated neoglycoproteins, in conjunction with subsequent avidin-peroxidase staining. It was shown that these tools were capable of revealing carbohydrate-binding sites during development of the rat cerebellum. The staining pattern with the individual probes disclosed variable developmental regulation and consequently suggested that recognition processes during cerebellar development may include several types of carbohydrate determinants. However, studies at the light microscope could not give information on potential membrane-bound localization of carbohydrate-binding sites and therefore discern the possible involvement of these molecules in cell adhesion processes. Furthermore, nuclear staining was suggested at the optical level. In order to elucidate these points, we examined the localization of mannose-, fucose- and heparin-binding sites at the electron microscopic level. Ultrastructural studies demonstrate that these tools are very efficient in detecting intracellular carbohydrate-binding sites, but failed to detect most of them expressed at the cell surface when using immunocytochemical techniques for known receptors, probably because of the interaction of these carbohydrate-binding sites with endogenous membrane-bound ligands. The significance of the nuclear staining and of part of the nucleolus found with fucose-containing neoglycoprotein and of the nuclear staining found with heparin are discussed.

Animals↗
PubMed1991

Malignant transformation in hepatocytes is associated with the general increase of glycoprotein ligands specifically binding to the endogenous lectin CSL.

Several hepatoma cell lines and hepatic ascite tumour cells were studied for the presence of glycoprotein ligands of an endogenous lectin, the "Cerebellar Soluble Lectin" (CSL). This lectin is also present in hepatocytes in vivo and in vitro and can be detected biochemically and immunologically. In transformed cells, the level of CSL glycoprotein ligands is increased 50-fold as compared to the control cells. Such an increase is not observed for the ligands of the plant lectin, concanavalin A, which is, as CSL, a D-mannose-binding lectin. These results indicated that the changes in glycans during malignant transformation, in these cells, is specifically important for minor glycans binding to CSL.

Animals↗
PubMed1991

Expression and localization in the developing cerebellum of the carbohydrate epitopes revealed by Elec-39, an IgM monoclonal antibody related to HNK-1.

The immunochemical and immunocytochemical reactivity of an anti-carbohydrate monoclonal antibody (Elec-39), obtained against acetylcholinesterase from Electrophorus electricus electric organ, was followed during the postnatal development of the rat cerebellum. The specificity of this antibody resembles that of a family of anti-carbohydrate antibodies that includes HNK-1, L2, NC-1 and NSP-4, as well as IgMs that occur in some human neuropathies. As revealed by immunoblotting techniques, the reactivity of Elec-39 is maximum around postnatal days 10-12. At this age, the antibody reveals eight major proteins of mol. wt ranging between 14 and 150 kDa. Some of them (with mol. wts of 14, 18, 28 and 31 kDa) are transiently expressed. They correspond to previously identified glycoproteins binding to the plant lectin concanavalin A and binding also to the endogenous mannose-binding lectin CSL and endogenous membrane-bound mannose-binding lectin. In young animals, an important staining with the Elec-39 antibody can be observed on postmitotic precursors of granule cells, on astrocyte processes in the external granular layer, on newly formed parallel fibres and on unmyelinated axons of the white matter. In adult animals, the labelling is localized essentially in myelin and also in the cytoplasm of astrocytes. These results are discussed in relation to ontogenetic phenomena occurring during cerebellar development and the potential role of the carbohydrate epitope revealed with Elec-39 as a determinant in cell adhesion processes.

Acetylcholinesterase↗
PubMed1991

The endogenous lectin cerebellar soluble lectin and its ligands in central nervous system myelin of myelin-deficient (mld) mutant mice.

The myelin-deficient (mld) mutation is autosomal recessive mutation in the murine CNS exhibiting severe hypomyelination. The primary defect results in a drastic reduction of myelin basic protein synthesis caused by a duplication of the myelin basic protein gene with partial inversion of the upstream gene copy. The severe deficit of myelin basic protein is responsible for the absence of the major dense line but cannot explain the heterogeneity of myelin compaction found in mld. We have tested the hypothesis that the endogenous cerebellar soluble lectin (CSL) and/or its endogenous glycoprotein ligands could be involved in myelin abnormalities in the dysmyelinating mutant, mld. Immunocytochemical and immunoblotting techniques showed that the CSL level was not reduced significantly in the mld mutant. Furthermore, two ligands of CSL, the myelin-associated glycoprotein and an axonal glycoprotein, with a relative molecular mass of 31 kDa, were not decreased in level in the purified myelin fraction isolated from mld mice. In contrast, three minor glycoprotein ligands of CSL of relative molecular mass of 23, 18, and 16 kDa were greatly reduced in content. The reduced concentration of these low-molecular-mass glycoproteins in mld myelin suggests that they are constituents of compact myelin. Furthermore, the observation that CSL is specifically localized in vivo in regions where mld myelin is more compact and absent from regions devoid of myelin compaction may suggest that the endogenous CSL lectin, as well as its minor glycoprotein ligands, plays a role in the stabilization of the myelin sheath.

Animals↗
PubMed1991

Involvement of the endogenous lectin CSL in adhesion of Chinese hamster ovary cells.

Immunochemical localization of an endogenous mannose-binding protein, the cerebellar soluble lectin (CSL; Zanetta et al., J. Neurochem. 49, 1250-1257 (1987)), in Chinese hamster ovary cells indicated its high concentration in areas of contact between cells. This suggested its role in cell adhesion. The pattern of staining differed significantly in the cells cultured in suspension from that grown as monolayer. In cells maintained for a short time as suspension, the extracellular CSL immunoreactivity was found mainly in close apposition to the plasma membrane including contact areas. In cells cultured as monolayer, extracellularly, the lectin was found both at the cell surface and in a 75-nm thick layer between two cells, apparently adhering to the cell surface through bridges. Endogenous glycoprotein ligands of CSL were present in the cultures of CHO cells, both as membrane-bound glycoproteins and as glycoprotein ligands soluble in the presence of mannose in the absence of detergent. The lectin CSL induced adhesion between these cells as evident by low concentration of anti-CSL Fab fragments inhibiting such adhesion. These data suggested that adhesion between CHO cells occurs, in part, through a glycobiological recognition system involving CSL. This mechanism should be taken into account for the interpretation of experiments of transfection in CHO cells of the genes of glycoproteins involved in cell adhesion.

Animals↗
PubMed1991

[Is Cerebellar Soluble Lectin a major immunological target in multiple sclerosis?].

In a recent paper: (Zanetta J.P. et al., Lancet, 1990, 335, 1482-1484) the authors showed that antibodies against the mannose-binding protein Cerebellar Soluble Lectin (CSL) are present in the cerebrospinal fluid of most multiple sclerosis patients. Herein, the properties and roles of the molecule as they are currently understood are described; hypotheses suggested by the consistent presence of anti-CSL antibodies in multiple sclerosis patients are discussed.

Antibodies↗
PubMed1990

Antibodies to cerebellar soluble lectin CSL in multiple sclerosis.

Cerebrospinal fluid samples from 239 patients with various neurological disorders were tested for the presence of autoantibodies to an endogenous mannose-binding protein, the cerebellar soluble lectin CSL, by means of an immunoblotting test with rat CSL as antigen. 47 of 51 patients with multiple sclerosis were positive for anti-CSL compared with 30 of 188 patients with other neurological disorders. 14 of the 30 false-positive patients were over 60 years old, an age group not typical of multiple sclerosis patients. The specificity of the test for multiple sclerosis was 85% and the sensitivity 93.5%. The possibility that CSL is an important immunological target in multiple sclerosis allows new insights into the possible causes and development of this disorder.

Adult↗
PubMed1990

An endogenous lectin and one of its neuronal glycoprotein ligands are involved in contact guidance of neuron migration.

In the central nervous system, postmitotic neurons migrate along astrocytic processes to reach their adult position. The molecular mechanisms of this guided migration are not clearly defined, although some steps have been shown to involve proteases and cell adhesion molecules. We report that monovalent antibodies (Fab fragments) raised against an endogenous cerebellar soluble lectin (CSL) completely inhibit neuronal migration in cultures of cerebellar explants at concentrations as low as 50 micrograms/ml. A similar inhibition pattern was obtained with Fab fragments prepared against one of the endogenous glycoprotein ligands of CSL, the 31-kDa glycoprotein (this glycoprotein is a membrane-bound glycoprotein specifically occurring, in the cerebellum, at the surface of immature neurons). We propose that this lectin-glycoprotein interaction supports the adhesion between neurons and the astrocyte guide during the migration of cerebellar immature neurons.

Animals↗