Showing papers on "Galectin published in 1996"

Galectins: A Family of Animal Lectins That Decipher Glycocodes

Abstract: Galectins, animal lectins exhibiting specificity for galactosides, are now known to be widely distributed from lower invertebrates, such as sponges and nematodes, to higher vertebrates. The origin of the family can be traced back to the Precambrian era. They are classified into proto-, chimera-, and tandem-repeat types on the basis of protein architecture. The molecular functions of these types should be different because they can cross-link pairs of biomolecules of different combinations. Their biological significance, however, is not yet fully understood because they are involved in too many phenomena, such as differentiation, morphogenesis, metastasis, etc., and too many problems remain unsolved, such as those regarding their controversial cellular localization, mechanism of externalization, etc. Nevertheless, such difficulties seem to indicate their importance as household equipment and their common roles throughout the animal kingdom. They are likely to be responsible for recognizing the N-acetyllactosamine (LacNAc) structure, which is included in various glycoconjugates and considered to be an important glycocode, and then carry out appropriate tasks under given circumstances. Recently, crystallographic studies revealed that galectins and legume lectins such as concanavalin A have a common topology in spite of the absence of sequence homology. This suggests a possible relationship between animal and plant lectins, and the existence of a lectin super family. Studies on the galectin family are becoming increasingly important for glycobiology.

ERGIC-53 is a functional mannose-selective and calcium-dependent human homologue of leguminous lectins.

Abstract: Based on sequence homologies with leguminous lectins, the intermediate compartment marker ERGIC-53 was proposed to be a member of a putative new class of animal lectins associated with the secretory pathway. Independent, a promyelocytic protein, MR60, was purified by mannose-column chromatography, and a cDNA was isolated that matched MR60 peptide sequences. This cDNA was identical to that of ERGIC-53 and homologies with the animal lectin family of the galectins were noticed. Not all peptide sequences of MR60, however, were found in ERGIC-53, raising the possibility that another protein associated with ERGIC-53 may possess the lectin activity. Here, we provide the first direct evidence for a lectin function of ERGIC-53. Overexpressed ERGIC-53 binds to a mannose column in a calcium-dependent manner and also co-stains with mannosylated neoglycoprotein in a morphological binding assay. By using a sequential elution protocol we show that ERGIC-53 has selectivity for mannose and low affinity for glucose and GlcNAc, but no affinity for galactose. To experimentally address the putative homology of ERGIC-53 to leguminous lectins, a highly conserved protein family with an invariant asparagine essential for carbohydrate binding, we substituted the corresponding asparagine in ERGIC-53. This mutation, as well as a mutation affecting a second site in the putative carbohydrate recognition domain, abolished mannose-column binding and co-staining with mannosylated neoglycoprotein. These findings establish ERGIC-53 as a lectin and provide functional evidence for its relationship to leguminous lectins. Based on its monosaccharide specificity, domain organization, and recycling properties, we propose ERGIC-53 to function as a sorting receptor for glyco-proteins in the early secretory pathway.

Surface-epitope masking and expression cloning identifies the human prostate carcinoma tumor antigen gene PCTA-1 a member of the galectin gene family

Abstract: The selective production of monoclonal antibodies (mAbs) reacting with defined cell surface-expressed molecules is now readily accomplished with an immunological subtraction approach, surface-epitope masking (SEM). Using SEM, prostate carcinoma (Pro 1.5) mAbs have been developed that react with tumor-associated antigens expressed on human prostate cancer cell lines and patient-derived carcinomas. Screening a human LNCaP prostate cancer cDNA expression library with the Pro 1.5 mAb identifies a gene, prostate carcinoma tumor antigen-1 (PCTA-1). PCTA-1 encodes a secreted protein of approximately 35 kDa that shares approximately 40% sequence homology with the N-amino terminal region of members of the S-type galactose-binding lectin (galectin) gene family. Specific galectins are found on the surface of human and marine neoplastic cells and have been implicated in tumorigenesis and metastasis. Primer pairs within the 3' untranslated region of PCTA-1 and reverse transcription-PCR demonstrate selective expression of PCTA-1 by prostate carcinomas versus normal prostate and benign prostatic hypertrophy. These findings document the use of the SEM procedure for generating mAbs reacting with tumor-associated antigens expressed on human prostate cancers. The SEM-derived mAbs have been used for expression cloning the gene encoding this human tumor antigen. The approaches described in this paper, SEM combined with expression cloning, should prove of wide utility for developing immunological reagents specific for and identifying genes relevant to human cancer.

Human T lymphotropic virus-I infection of human T lymphocytes induces expression of the beta-galactoside-binding lectin, galectin-3.

Abstract: Animal lectins play important roles in a variety of biological processes via their recognition of glycoconjugates. Galectin-3 is a beta-galactoside-binding lectin previously designated as epsilon BP (IgE-binding protein), CBP35, Mac-2, L-29, and L-34, and its expression has been associated with various physiological and pathological processes, including cell growth, tumor transformation, and metastasis. Galectin-3 is widely distributed in various tissues and cell types and is expressed in many leukocytes, with the notable exception of B and T lymphocytes. We now report that galectin-3 is abundantly expressed in a number of human T lymphotropic virus (HTLV)-I-infected human T cell lines, including F6T, HUT 102, K3T, MT-2, and SLB-I, but is not expressed in non-HTLV-I-infected T cell lines such as Jurkat, CEM, and MOLT-4. In addition, the galectin-3 level was markedly increased in human thymocytes after infection with HTLV-I as compared with uninfected thymocytes. The up-regulation of galectin-3 expression appeared to correlate well with HTLV-I gene expression, as undetectable or very low levels of galectin-3 were found in the S1T and ATL-1K cell lines, which are nonproductively infected with HTLV-I. In co-transfection experiments, the galectin-3 promoter was significantly up-regulated by expression vectors encoding the 40-kd Tax protein, a potent transactivator in HTLV-I. Analysis of various Tax mutants suggested that galectin-3 promoter induction is dependent on activation of the cyclic-AMP-responsive element binding protein/activation transcription factor family of transcription factors and, to a lesser extent, nuclear factor-kappa B/Rel induction. Transfection of human promonocytic U-937 cells with an HTLV-I Tax expression vector induced galectin-3 expression in this cell line. Functionally, galectin-3 was shown to activate interleukin-2 production in Jurkat T cells. Together, these findings raise the possibility that HTLV-I Tax production induces the transcription and subsequent synthesis and secretion of galectin-3, which in turn may further activate these T cells and contribute to the altered properties of cell growth found in adult T cell leukemia induced by HTLV-I.

Identification and characterization of up-regulated genes during chondrocyte hypertrophy

Abstract: Chondrocyte hypertrophy involves de novo acquisition and/or increased expression of certain gene products including, among others, type X collagen, alkaline phosphatase, and matrix metalloproteinases. To analyze further the genetic program associated with chondrocyte hypertrophy, we have employed a modification of the polymerase chain reaction-mediated subtractive hybridization method of Wang and Brown (Wang and Brown [1991] Proc. Natl. Acad. Sci 88:11505). Cultures of hypertrophic tibial chondrocytes and nonhypertrophic sternal cells were used for poly A+ RNA isolation. Among 50 individual cDNA fragments isolated for up-regulated hypertrophic genes, 18 were tentatively identified by their similarities to entries in the GenBank database, whereas the other 32 showed no significant similarity. The identified genes included translational and transcriptional regulatory factors, ribosomal proteins, the enzymes transglutaminase and glycogen phosphorylase, type X collagen (highly specific for hypertrophic cartilage matrix), gelsolin, and the carbohydrate-binding protein galectin. Two of these, transglutaminase and galectin, were cloned and were further characterized. The chondrocyte transglutaminase revealed previously in hypertrophic cartilage by immunochemical methods appears to be the chicken equivalent of mammalian factor XIIIa (showing 75% overall protein similarity). The chicken chondrocyte galectin is a variant of mammalian galectin-3. Galectins are known to bind to components found in hypertrophic cartilage, and factor XIIIa is known to crosslink some of the same components, possibly modifying them for calcification and/or removal. © 1996 Wiley-Liss, Inc.

Comparative cross-linking activities of lactose-specific plant and animal lectins and a natural lactose-binding immunoglobulin G fraction from human serum with asialofetuin

Abstract: Plant and animal lectins bind and cross-link certain multiantennary oligosaccharides, glycopeptides, and glycoproteins. This can lead to the formation of homogeneous cross-linked complexes, which may differ in their stoichiometry depending on the nature of the sugar receptor involved. As a precisely defined ligand, we have employed bovine asialofetuin (ASF), a glycoprotein that possesses three asparagine-linked triantennary complex carbohydrate chains with terminal LacNAc residues. In the present study, we have compared the carbohydrate cross-linking properties of two Lac-specific plant lectins, an animal lectin and a naturally occurring Lac-binding polyclonal immunoglobulin G subfraction from human serum with the ligand. Quantitative precipitation studies of the Lac-specific plant lectins, Viscum album agglutinin and Ricinus communis agglutinin, and the Lac-specific 16 kDa dimeric galectin from chicken liver demonstrate that these lectins form specific, stoichiometric cross-linked complexes with ASF. At low concentrations of ASF, 1:9 ASF/lectin (monomer) complexes formed with both plant lectins and the chicken lectin. With increasing concentrations of ASF, 1:3 ASF/lectin (monomer) complexes formed with the lectins irrespective of their source or size. The naturally occurring polyclonal antibodies, however, revealed a different cross-linking behavior. They show the formation of 1:3 ASF/antibody (per Fab moiety) cross-linked complexes at all concentrations of ASF. These studies demonstrate that Lac-specific plant and animal lectins as well as the Lac-binding immunoglobulin subfraction from specific stoichiometric cross-linked complexes with ASF. These results are discussed in terms of the structure-function properties of multivalent lectins and antibodies.

Expression of galectins in head and neck squamous cell carcinoma

Abstract: Background Galectins are carbohydrate-binding proteins thought to be important for cell growth and differentiation, whose expression is altered in some tumors with aggressive phenotype. Our objective was to evaluate the expression of galectins in head and neck squamous cell carcinoma (HNSCC). Methods Fourteen HNSCC cell lines and four primary tumor specimens were evaluated using immunoblotting, and immunohistochemical analysis was performed on 35 primary HNSCCs. Results Galectin-1 and galectin-3 were expressed in most HNSCC cell lines and primary tumor specimens. Galectin-1 was detected in the basal layer of normal adjacent mucosa, in connective tissue stroma, and at the periphery of invasive tumor islands. Galectin-3 localized to superficial mucosal layers, and adjacent to keratin pearls is in invasive carcinoma. Conclusions Galectins are manifested in HNSCC tumors and are localized to the cell surface, where they may participate in cellular interactions. The expression pattern of galectins appears to be associated with degree of squamous differentiation, suggesting a potential role for galectins as biologic and differentiation markers in HNSCC. HEAD & NECK 1996;18:422–432 © 1996 John Wiley & Sons, Inc.

IMMUNOCYTOCHEMICAL EVIDENCE FOR A MODULATION OF GALECTIN 3 (Mac‐2), A CARBOHYDRATE BINDING PROTEIN, IN PULMONARY FIBROSIS

Abstract: Galectin 3 is an endogenous mammalian carbohydrate-binding protein with affinity for terminal β-galactose residues, polylactosamine glycans, and ABH-blood group carbohydrate epitopes. To determine the distribution and regulation of galectin 3 during pulmonary injury, which is known to be accompanied by profound changes in the carbohydrate moieties of cell surface glycoproteins of alveolar cells, a rat model of irradiation-induced lung inflammation and repair was used. Immunocytochemistry showed that in normal rat lungs, galectin 3 was localized to alveolar macrophages, with weaker staining of bronchial epithelial cells. Shortly after irradiation-induced lung injury, when there is active proliferation of type II alveolar epithelial cells and re-epithelialization of alveolar basement membranes by type I cells, the total galectin concentration in the lung increased dramatically. This increase was due in part to an increased population of galectin 3-positive interstitial and alveolar macrophages. In addition, galectin 3 was expressed prominently at the surface of the newly formed type I alveolar epithelium and to lesser extent at the apical surface of type II cells. These findings suggest that the increased synthesis and secretion of galectin 3 during irradiation-induced lung injury, together with ligation of secreted lectin at the surface of alveolar epithelial cells, may play roles in pulmonary alveolar epithelial expansion and differentiation during injury and repair.

Regulated expression of a 16-kd galectin-like protein in activated rat macrophages.

Abstract: We investigated the presence of a galectin-like protein in rat mononuclear cells using a polyclonal antibody raised against a soluble lactose-binding lectin purified from adult chicken liver that immunoreacted strongly with a broad protein band of about 16 kd in Western blot assays. Immunochemical studies revealed a constitutive expression of this protein in mononuclear cells mainly in the macrophage (M phi) population. Subcellular localization was assessed by Western blot assays of the cytosolic and membrane fractions of different cell populations studied: (1) spleen mononuclear cells, (2) T cell-enriched, (3) B cell- and M phi-enriched populations, and (4) peritoneal cells, processed in the presence of lactose. In broad agreement with immunocytochemical studies of nonpermeabilized and permeabilized cells, Western blot assays suggest that this protein is localized mainly in the cytoplasmic compartment but also associated with the cell surface. By flow cytometric analyses we detected about a 14% of ED1 double-positive cells corresponding to macrophages that constitutively express this galectin-like protein associated with their cell surface. The cytosolic fraction obtained from the M phi-enriched cell population showed hemagglutinating activity specifically inhibited by beta-galactoside-related sugars. Moreover, this galectin-like protein was retained in a lactosyl-Sepharose matrix and specifically eluted with lactose. In this work, evidence is also provided to show that different stimuli are able to modulate the expression of the galectin-like protein. Expression was upregulated in inflammatory and activated macrophages, revealing a significant increase in phorbol ester- and formylmethionine oligopeptide-treated cells. Both stimuli involving protein kinase C activation pathway have been able not only to up-regulate the total expression of this protein but also to modulate its subcellular localization.

A galectin links the aggregation factor to cells in the sponge (Geodia cydonium) system

Abstract: The cDNA for the full-length lectin from the marine sponge Geodia cydonium was cloned. Analysis of the deduced aa sequence revealed that this lectin belongs to the group of galectins. The full-length galectin, which was obtained also in a recombinant form, has an M(r) of 20,877; in the processed form it is a 15 kDa polypeptide. The enriched aggregation factor from G.cydonium also was determined to contain, besides minimal amounts of the galectin, a 140 kDa polypeptide which is involved in cell-cell adhesion. Monoclonal antibodies have been raised against this protein; Fab' fragments prepared from them abolished cell-cell reaggregation. Cell reaggregation experiments revealed that the aggregation factor is an essential component in the aggregation process but it requires likewise the presence of the galectin. Antibodies against the galectin blocked the aggregation factor-mediated cell adhesion. A plasma membrane component was identified (a 29 kDa polypeptide) which interacted with the aggregation factor in the presence of galectin; binding could be blocked both by antibodies against the galectin as well as against the aggregation factor. Immunohistochemical analysis revealed that spherulous cells contain the galectin but not the aggregation factor. By laser scanning microscopy, it is shown that both the aggregation factor and the galectin are located at the rim of the cells. From these data we conclude that the G.cydonium aggregation factor binds to the cells via a galectin bridge.

Galectin-1 from Bovine Spleen: Biochemical Characterization, Carbohydrate Specificity and Tissue-Specific Isoform Profiles.

Abstract: Selected biochemical properties, including the charge heterodispersity profile and carbohydrate specificity, of bovine galectin-1 were determined in detail. The lectin was purified through an improved purification protocol that yielded 35-40 mg/kg of wet tissue with a specific activity of 1.7-2 x 10(4) mg-1.ml. The galectin is a homodimer of approximately 14.5 kDa subunits with E(280)mg/ml of 0.65 ml.mg-1.cm-1. When stored in the presence of its carbohydrate ligand, the lectin's binding activity remained stable in a non-reducing environment even at room temperature. The optimal pH for binding to the ligand was 6.5-8.0. The overall carbohydrate specificity of the bovine galectin-1 isolated from spleen is similar to that of the galectin isolated from heart and to other mammalian galectins that exhibit "conserved" (Type I) carbohydrate recognition domains (CRDs) [Ahmed, H. and Vasta, G.R. (1994) Glycobiology 4, 545-549], but differs from those from Xenopus laevis and rat intestine domain I. The fluorescence of 4-methylumbelliferyl alpha-D-galactopyranoside was quenched on binding to bovine spleen galectin-1. Scatchard plots of data obtained at 5, 15, and 30 degrees C showed that the galectin has two sugar exothermic binding sites with association constants of 3.4 x 10(5), 1.0 x 10(5), and 0.3 x 10(5), respectively. Chemical modification studies indicated that histidine, tryptophan, carboxylic acid, and arginine, but not lysine or tyrosine, are involved in the binding to the carbohydrate ligand. On isoelectric focusing, the spleen galectin-1 appeared as six isoforms ranging from pI4.56-4.88 with main components at pI 4.63 (34.0%), 4.73 (42.6%), and 4.88 (16.6%). The galectin-1 isolated from heart yielded a quali- and quantitatively different profile with four isoforms ranging from pI 4.53-4.73, those with pIs of 4.56, 4.63, and 4.73 being common to the spleen homolog. Edman degradation of selected peptides purified from the spleen galectin-1 digest revealed amino acid sequences identical to those obtained for the heart galectin-1. This suggests that although point mutations in the subunit primary structure may not be the likely source of isolectins, as observed for X. laevis, tissue-specific co- or post-translational modifications may be the possible cause of the differences in the galectin isoform profile between bovine spleen and heart.

An immunohistochemical study of the 32-kda galectin (beta -galactoside-binding lectin) in the nematode caenorhabditis elegans

Abstract: The localization of the 32-kDa galectin (β-galactoside-binding lectin) of the nematodeCaenorhabditis elegans, which is the first lectin to be found in a nematode, was examined immunohistochemically using an anti-lectin antiserum. The lectin was found to be localized most abundantly in the adult cuticle and also in the terminal bulb of the pharynx. However, it was difficult to locate the galectin in larval animals, though immunochemical experiments suggested its presence. These results suggest that one of the fundamental roles of the galectin may be as a component of the durable outer barrier, as in the case of the morphogenesis of chick embryonic skin.

Forssman disaccharide is the specific ligand of a galectin from the sponge Geodia cydonium but does not mediate its binding to nuclear protein np56.

Abstract: The galectin from Geodia cydonium (GCA) had previously been shown to be involved in regulatory mechanisms of cell sorting and adhesion during reaggregation of allogeneic sponge cells. In this contribution the binding specificity of GCA was established to be GalNAc alpha 1-3GalNAc beta as structural component of Forssman pentasaccharide. Crossreactivities of terminal structural elements were revealed in the order GalNAc alpha 1-3GalNAc beta > GalNAc alpha 1-3(Fuc alpha 1-2)Gal beta >> Gal beta 1-3GlcNAc beta > Gal beta 1-4Glc. Lectin binding to the Forssman antigen (Ki range 10(-7)) or to blood group A-trisaccharide exceeded that to lactose (Ki range 10(-3)/10(-2)) by three to four orders of magnitude. Cytochemical staining of eukaryotic cells on the light and electron microscopic level revealed lectin binding in the cytosol and in the nucleus (nucleoli), which was inhibitable with the soluble high affinity ligands. The nuclear binding of GCA could be ascribed to affinity-isolated 56 kDa protein (np56) in the nucleoplasm and was shown to be mediated by the peptide conformation of the ligand. Although GCA-np56 interaction was inhibitable with Forssman glycolipid or globopentaose, the carbohydrate binding site of the lectin is not involved due to the lack of competition by Forssman-specific lectins HPA or DBA. Since anti-CBP70 was immunologically cross-reactive to np56, it is concluded that the galectin GCA binds to np56 via similar mechanisms as reported previously for the interaction of CBP-35 (galectin-3) and CBP-70. Thus, GCA resembles galectin-3 in its binding characteristics but is likewise related to galectin-1 by sequence homology of its primary structure and by the molecular mass of its subunits.

Identification of different galectins by immunoblotting after two‐dimensional polyacrylamide gel electrophoresis with immobilized pH gradients

Abstract: Vertebrate soluble beta-galactoside-binding lectins form a growing protein family that recently have been named galectins. Seven different galectins have been sequenced and characterized in mammals, and there is compelling evidence for the existence of other members of this lectin family. Three among six galectins are homodimers with (i) an identical subunit of a relative molecular mass of about 14500, and (ii) amino acid sequence homologies giving rise to possible immunochemical cross-reactivities. They are indistinguishable from each other by conventional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), even when followed by immunoblotting. However, their different isoelectric points allow their identification using isoelectric focusing and two-dimensional (2-D) polyacrylamide gel electrophoresis. A strategy was developed to identify these galectins in crude extracts from cells and tissues, based on the two-dimensional electrophoresis with immobilized pH gradient (IPG-Dalt) analysis of the specific spots of purified galectins and of the spots of crude extracts, after silver staining. In addition, 2-D immunoblotting using anti-galectin 1 (Gal-1) and anti carbohydrate-binding protein 15 (CPB15) antibodies were performed on brain and leukemia cells (HL60) allowing an identification of related polypeptides. Our results indicate that the use of IPG-Dalt provides a suitable reproducibility and allows the detection of galectins or other galactoside-binding proteins even at basic pIs.

Signaling mechanisms in protozoa and invertebrates

Abstract: Evolutionary Significance of the Hormone Recognition Capacity in Unicellular Organisms. Development of Hormone Receptors.- 1 Introduction.- 2 Receptor Memory: Hormonal Imprinting.- 3 Problems of the Specificity of Imprinting.- 4 Time, Concentration, and Downregulation.- 5 Sugars of the Receptors.- 6 Cell Aging and Imprinting.- 7 Imprinting by Amino Acids and Oligopeptides.- 8 Receptors of the Nuclear Envelope.- 9 Possible Mechanisms of Imprinting.- 10 The Other Component: Hormones in Protozoa.- 11 Evolutionary Conclusions Based on the Unicellular Model.- References.- Studies on the Opioid Mechanism in Tetrahymena.- 1 Introduction to Opioid Mechanisms.- 1.1 Opioid Mechanisms in Invertebrate Metazoa.- 1.2 Opioid Mechanisms in Unicellular Organisms.- 2 The Opioid Mechanism in Tetrahymena.- 2.1 Pharmacological Characterization of the Endogenous Opioid.- 2.2 Pharmacological Characterization of the Opioid Receptor.- 2.3 Biochemical Characterization of the Signal Transduction Pathway.- 3 Conclusions.- References.- Adenylate and Guanylate Cyclases in Tetrahymena.- 1 Introduction.- 2 Cyclic Nucleotide Metabolism in Tetrahymena.- 2.1 Cell Growth- and Cycle-Associated Changes.- 2.2 Involvement in Biological Regulation.- 3 Cyclases Involved in Cell Metabolism and Functions.- 4 Regulatory Mechanisms of Cyclases.- 4.1 Adenylate Cyclase.- 4.2 Guanylate Cyclase.- 5 Structure and Intracellular Distribution of Calmodulin.- 6 Conclusion.- References.- Signal Peptide-Induced Sensory Behavior in Free Ciliates: Bioassays and Cellular Mechanisms.- 1 Introduction.- 2 Peptide Signals in Ciliates.- 2.1 Signal Peptides Found Intracellularly.- 2.2 Signal Peptides Having Sensory Effects.- 2.2.1 Physiological Effects of Insulin on Tetrahymena.- 3 Bioassays Measuring Peptide-Induced Changes of Cell Behavior and Ciliary Activity.- 3.1 Population Assays for Chemoattraction.- 3.2 Single Cell Assays for Chemoattraction.- 3.3 Assays of Ciliary Activity.- 4 Cellular Mechanisms Related to Peptide Action on Individual Cell Behavior.- 4.1 Adaptation.- 4.2 Persistence.- 5 Concluding Remarks.- References.- Ciliate Pheromones.- 1 Introduction.- 2 Background.- 3 Pheromone Notation and Origin.- 4 Pheromone Secretion and Purification.- 5 Pheromone Structure.- 6 Pheromone Genes.- 7 Pheromone Receptors.- 8 Competitive Pheromone Receptor-Binding Reactions.- 9 Pheromones as Growth Factors.- 10 Concluding Remarks.- References.- Cell-Surface GPI Expression in Protozoa. The Connection with the PI System.- 1 Introduction.- 1.1 The GPI Anchor.- 1.2 The GPI Anchor Biosynthesis.- 1.3 Enzymes with Specificities for GPI Anchors.- 1.4 The Inositol Phospholipids and Signal Transduction.- 2 The Cell-Surface Expression of GPI-Anchored Proteins in the Protozoa.- 2.1 GPI-Anchored Proteins in the Parasitic Protozoa.- 2.2 GPI-Anchored Proteins in the Free-Living Protozoa.- 3 Inositol Phospholipids in Tetrahymena pyriformis. The Possible Link Between the PI System and Synthesis of GPI.- References.- Cell Adhesion Proteins in the Nonvertebrate Eukaryotes.- 1 Introduction.- 1.1 History and Philosophy.- 1.2 Evolution.- 2 Approaches and Findings.- 3 Protista.- 3.1 Trypanosoma cruzi.- 3.2 Cellular Slime Molds.- 4 Higher Eukaryotes.- 5 An Alveolate: Plasmodium.- 6 Plants.- 6.1 Chlamydomonas.- 6.2 Volvox.- 6.3 Higher Plants.- 7 Fungi.- 7.1 Saccharomyces cerevisiae.- 7.2 Candida.- 8 Metazoa.- 8.1 Sponges.- 8.2 Cnidaria: Hydra.- 8.3 Tripoblasts.- 8.3.1 Pseudocoelatomates: Caenorhabditis elegans.- 8.4 Insects.- 8.5 Deuterostomes.- 8.5.1 Fertilization in Sea Urchins.- 9 Conclusions.- 10 Characteristics of Cell Adhesion Proteins.- 10.1 Modules.- 10.2 Cell Surface Association.- 10.3 Role of Ca2+.- 10.4 Binding Characteristics.- 11 Extracellular Matrix Interactions.- 12 Role of Lectins and Carbohydrates.- 13 Signal Transduction and Cytoplasmic Domains.- References.- Animal Lectins as Cell Surface Receptors: Current Status for Invertebrate Species.- 1 Introduction.- 2 Animal Lectins as Cell Membrane Receptors.- 3 Lectin Families in Invertebrate and Protochordate Species. Their Association with the Hemocyte Plasma Membrane.- 4 Summary and Prospects.- References.- Characterization of the Receptor Protein-Tyrosine Kinase Gene from the Marine Sponge Geodia cydonium.- 1 Introduction.- 2 Protein Kinases.- 3 Receptor Protein-Tyrosine Kinases.- 4 Receptor Protein-Tyrosine Kinase from the Sponge Geodia cydonium.- 4.1 Ligand-Binding Domain (Immunoglobulin-Like Domain).- 4.2 Intron/Exon.- 4.3 Transmembrane Domain.- 4.4 Juxtamembrane Region.- 4.5 Catalytic Domain.- 4.6 3?-Nontranslated Region.- 5 Proposed Function of the Sponge Receptor Protein-Tyrosine Kinase.- 6 Implication for Molecular Evolution of Metazoa.- 7 Summary and Perspectives.- References.

Prognostic relevance of detection of ligands for vertebrate galectins and a Lewis(Y)-specific monoclonal antibody.

Abstract: Tissue sections taken from 157 potentially curatively operated lung carcinoma patients (70 epidermoid carcinomas, 68 adenocarcinomas, 15 large cell anaplastic, and 4 small cell anaplastic carcinomas) were examined by a standardized histochemical protocol in a prospective study evaluating the extent of various types of probes to serve as prognostic indicators in lung cancer. Detailed clinical records and survival data (minimum 56 weeks, maximum 96 weeks) were correlated to the results of the histochemical reactions. The study centres on monitoring the expression of galactoside-containing epitopes in tumor cells by human, animal and plant lectins: and with a monoclonal antibody. In addition, affinity-purified subfractions of natural antibodies from human serum with preferential affinity to alpha- and beta-galactosides, respectively, were employed. Significant contributions to the estimation of the survival of patients are given by clinical parameters (pT, pN stage), number of resected and positive lymph nodes and presence of tumor metastases into specific lymph nodes (No. 5 and No. 6 right and left). With respect to the relevance of subsets of beta-galactosides, the galectin from chicken liver (CL-16) and the Le(y)-specific monoclonal antibody unveiled a negative correlation at a statistically significant level. The predictive value of binding of the animal lectin CL-16 was especially pronounced for patients with advanced tumor stages, pointing to a potential role of such lectin-reactive beta-galactosides in late tumor stages or progression.

A new family of lectins

Abstract: Lectins are defined as carbohydrate binding proteins other than enzymes and antibodies. Until recently, lectins were considered to be exclusively plant proteins and as such drew only limited attention of biochemists. As soon as they were detected in animal cells and after their involvement in vital processes such as development, differentiation and neoplastic growth was recognized, widespread studies have focused on their specificity, structure, localization and specific biological functions. Very recently, several p-galactose specific lectins were organized into a new lectin family - galectins. Members of this family are present in nearly all animals, from lower invertebrates such as sponges and nematodes to mammals, including humans. Though not completely understood, the awareness of their physiological importance is increasing as their properties are unraveled, and the interest in them is ascending as multiple implications of their presence are emerging.

[Isolation and characteristics of galactose-binding lectins from human blood serum].

Abstract: Two galactose-binding lectins, SL1 and SL2, were isolated from human serum by two-step affinity chromatography on sorbents with immobilized disaccharides Gal beta 1-3GlcNAc beta (Lec) and Fuc alpha 1-2Gal beta (Hdi). The purification degree of the SL1 and SL2 preparations was 4000-6000 times and yields were 6.9 and 4.7 micrograms/ml of serum, respectively. Electrophoresis showed that both lectins are oligomers with molecular masses of about 440 kDa, which are composed of ca. 67 kDa subunits. The carbohydrate specificity of the lectins was assayed by hemagglutination inhibition using mono- and oligosaccharides. Both lectins showed specificity for Gal and GalNAc residues but differed in the interactions with oligosaccharides. In particular, SL1 showed maximum affinity for disaccharide Gal beta 1-3GalNAc beta (in the form of 4-nitrophenyl glycoside), 6'-sialyllactose, and disaccharide residues Fuc alpha 1-3Gal beta and Gal alpha 1-3Gal beta, whereas SL2 was specific for GalNAc alpha residue and its derivatives as well as for disaccharide Hdi.

A Novel β-Galactoside-Binding Lectin in Cultured Murine Lymphocytic Leukemia Cells

Abstract: Using affinity chromatography on lactosyl-Sepharose, a beta-galactoside-binding protein of 38 kDa was detected in mouse L1210 lymphocytic leukemia cells. Immunoblotting analysis revealed that it is distinct from any known larger molecular weight galectin. The partial amino acid sequences of the 38 kDa protein indicated that it is a novel member of the galectin family. This 38 kDa lectin is expressed in lymphocytic cell lines but not macrophage-like cell lines.