The role of Globo H and SSEA-4 in the development and progression of cancer, and their potential as therapeutic targets.

Glycans, chains of sugar molecules found conjugated to cell proteins and lipids, contribute to their growth, movement and differentiation. Aberrant glycosylation is a hallmark of several medical conditions including tumorigenesis. Glycosphingolipids (GSLs), consisting of glycans conjugated to a lipid (ceramide) core, are found in the lipid bilayer of eukaryotic cell membranes. GSLs, play an active role in cell processes. Several GSLs are expressed by human embryonic stem cells and have been found to be overexpressed in several types of cancer. In this review, we discuss the data, hypotheses and perspectives related to the GSLs Globo H and SSEA-4.

Glycoconjugate vaccine using a genetically modified O antigen induces protective antibodies to Francisella tularensis.

Francisella tularensis is the causative agent of tularemia, a category A bioterrorism agent. The lipopolysaccharide (LPS) O antigen (OAg) of F. tularensis has been considered for use in a glycoconjugate vaccine, but conjugate vaccines tested so far have failed to confer protection necessary against aerosolized pulmonary bacterial challenge. When F. tularensis OAg was purified under standard conditions, the antigen had a small molecular size [25 kDa, low molecular weight (LMW)]. Using milder extraction conditions, we found the native OAg had a larger molecular size [80 kDa, high molecular weight (HMW)], and in a mouse model of tularemia, a glycoconjugate vaccine made with the HMW polysaccharide coupled to tetanus toxoid (HMW-TT) conferred better protection against intranasal challenge than a conjugate made with the LMW polysaccharide (LMW-TT). To further investigate the role of OAg size in protection, we created an F. tularensis live vaccine strain (LVS) mutant with a significantly increased OAg size [220 kDa, very high molecular weight (VHMW)] by expressing in F. tularensis a heterologous chain-length regulator gene (wzz) from the related species Francisella novicida Immunization with VHMW-TT provided markedly increased protection over that obtained with TT glycoconjugates made using smaller OAgs. We found that protective antibodies recognize a length-dependent epitope better expressed on HMW and VHMW antigens, which bind with higher affinity to the organism.

Sialylated Oligosaccharides and Glycoconjugates of Human Milk. The Impact on Infant and Newborn Protection, Development and Well-Being.

Human milk not only has nutritional value, but also provides a wide range of biologically active molecules, which are adapted to meet the needs of newborns and infants. Mother's milk is a source of sialylated oligosaccharides and glycans that are attached to proteins and lipids, whose concentrations and composition are unique. Sialylated human milk glycoconjugates and oligosaccharides enrich the newborn immature immune system and are crucial for their proper development and well-being. Some of the milk sialylated oligosaccharide structures can locally exert biologically active effects in the newborn's and infant's gut. Sialylated molecules of human milk can be recognized and bound by sialic acid-dependent pathogens and inhibit their adhesion to the epithelial cells of newborns and infants. A small amount of intact sialylated oligosaccharides can be absorbed from the intestine and remain in the newborn's circulation in concentrations high enough to modulate the immunological system at the cellular level and facilitate proper brain development during infancy. Conclusion: The review summarizes the current state of knowledge on sialylated human milk oligosaccharides and glycoconjugates, discusses the significance of sialylated structures of human milk in newborn protection and development, and presents the advantages of human milk over infant formula.

Glycoconjugates reveal diversity of human neural stem cells (hNSCs) derived from human induced pluripotent stem cells (hiPSCs).

Neural stem cells (NSCs) have the ability to self-renew and to differentiate into various cell types of the central nervous system. This potential can be recapitulated by human induced pluripotent stem cells (hiPSCs) in vitro. The differentiation capacity of hiPSCs is characterized by several stages with distinct morphologies and the expression of various marker molecules. We used the monoclonal antibodies (mAbs) 487LeX, 5750LeX and 473HD to analyze the expression pattern of particular carbohydrate motifs as potential markers at six differentiation stages of hiPSCs. Mouse ESCs were used as a comparison. At the pluripotent stage, 487LeX-, 5750LeX- and 473HD-related glycans were differently expressed. Later, cells of the three germ layers in embryoid bodies (hEBs) and, even after neuralization of hEBs, subpopulations of cells were labeled with these surface antibodies. At the human rosette-stage of NSCs (hR-NSC), LeX- and 473HD-related epitopes showed antibody-specific expression patterns. We also found evidence that these surface antibodies could be used to distinguish the hR-NSCs from the hSR-NSCs stages. Characterization of hNSCsFGF-2/EGF derived from hSR-NSCs revealed that both LeX antibodies and the 473HD antibody labeled subpopulations of hNSCsFGF-2/EGF. Finally, we identified potential LeX carrier molecules that were spatiotemporally regulated in early and late stages of differentiation. Our study provides new insights into the regulation of glycoconjugates during early human stem cell development. The mAbs 487LeX, 5750LeX and 473HD are promising tools for identifying distinct stages during neural differentiation.

Sugar Coating the Envelope: Glycoconjugates for Microbe-Host Crosstalk.

Tremendous progress has been made on mapping the mainly bacterial members of the human intestinal microbiota. Knowledge on what is out there, or rather what is inside, needs to be complemented with insight on how these bacteria interact with their biotic environment. Bacterial glycoconjugates, that is, the collection of all glycan-modified molecules, are ideal modulators of such interactions. Their enormous versatility and diversity results in a species-specific glycan barcode, providing a range of ligands for host interaction. Recent reports on the functional importance of glycosylation of important bacterial ligands in beneficial and pathogenic species underpin this. Glycoconjugates, and glycoproteins in particular, are an underappreciated, potentially crucial, factor in understanding bacteria-host interactions of old friends and foes.

A glycoconjugate of Haemophilus influenzae Type b capsular polysaccharide with tetanus toxoid protein: hydrodynamic properties mainly influenced by the carbohydrate.

Three important physical properties which may affect the performance of glycoconjugate vaccines against serious disease are molar mass (molecular weight), heterogeneity (polydispersity), and conformational flexibility in solution. The dilute solution behaviour of native and activated capsular polyribosylribitol (PRP) polysaccharides extracted from Haemophilus influenzae type b (Hib), and the corresponding glycoconjugate made by conjugating this with the tetanus toxoid (TT) protein have been characterized and compared using a combination of sedimentation equilibrium and sedimentation velocity in the analytical ultracentrifuge with viscometry. The weight average molar mass of the activated material was considerably reduced (Mw ~ 0.24 × 10(6) g.mol(-1)) compared to the native (Mw ~ 1.2 × 10(6) g.mol(-1)). Conjugation with the TT protein yielded large polydisperse structures (of Mw ~ 7.4 × 10(6) g.mol(-1)), but which retained the high degree of flexibility of the native and activated polysaccharide, with frictional ratio, intrinsic viscosity, sedimentation conformation zoning behaviour and persistence length all commensurate with highly flexible coil behaviour and unlike the previously characterised tetanus toxoid protein (slightly extended and hydrodynamically compact structure with an aspect ratio of ~3). This non-protein like behaviour clearly indicates that it is the carbohydrate component which mainly influences the physical behaviour of the glycoconjugate in solution.

Lectin staining of the uterovaginal junction and sperm-storage tubule epithelia in broiler hens.

Mammalian sperm bind to terminal carbohydrates associated with glycoconjugates on the apical surface of oviduct epithelial cells in the caudal region of the oviduct and undergo cellular and molecular modifications associated with capacitation prior to ovulation. In contrast, chicken sperm are stored for up to 23 d in sperm-storage tubules (SST) localized in the uterovaginal junction (UVJ). Little is known of the cellular and molecular mechanisms that regulate sperm storage in and release from the SST. The purpose of this study was to identify glycoconjugates associated with the SST epithelial cell surface using lectins. Virgin hens and hens of higher and lower fertility in egg production for 6 to 16 wk were used in this study. Sections of UVJ mucosa containing SST were stained with fluorescent conjugated lectins and examined by confocal microscopy. Carbohydrate moieties associated with the UVJ and SST epithelia differed in their lectin binding patterns. No differences in the lectin binding patterns within the 2 epithelia were discernible between the virgin and younger and older hens. Minor differences were observed between the higher and lower fertility hens. Only lectins specific for galactose and N-acetylgalactosamine moieties were localized to the luminal surface of the SST. While resident sperm may be closely apposed to the SST epithelial cell apical microvilli, it is unlikely that sperm binding to the microvilli via terminal carbohydrates associated with glycoconjugates is a requisite for prolonged storage. However, the possibility of SST epithelial cell communication with resident sperm via shedding microvillous vesicles characterized by surface glycoconjugates with terminal galactose and N-acetylgalactosamine moieties is currently being investigated.

Lactobacillus rhamnosus GG SpaC pilin subunit binds to the carbohydrate moieties of intestinal glycoconjugates.

Lactobacillus rhamnosus GG (LGG) is a well-established probiotic strain. The beneficial properties of this strain are partially dependent on its prolonged residence in the gastrointestinal tract, and are likely influenced by its adhesion to the intestinal mucosa. The pilin SpaC subunit, located within the Spa pili structure, is the most well studied LGG adhesion factor. However, the binding epitopes of SpaC remain largely unknown. The aim of this study was to evaluate the binding properties of SpaC to the carbohydrate moieties of intestinal glycoconjugates using a recombinant SpaC protein. In a competitive enzyme-linked immunosorbent assay, SpaC binding was markedly reduced by addition of purified mucin and the mucin oligosaccharide fraction. Histochemical staining revealed that the binding of SpaC was drastically reduced by periodic acid treatment. Moreover, in the surface plasmon resonance-based Biacore assay, SpaC bound strongly to the carbohydrate moieties containing ß-galactoside at the non-reducing terminus of glycolipids. We here provide the first demonstration that SpaC binds to the oligosaccharide chains of mucins, and that the carbohydrate moieties containing ß-galactoside at the non-reducing termini of glycoconjugates play a crucial role in this binding. Our results demonstrate the importance of carbohydrates of SpaC for mucus interactions.

Glycobiology of reproductive processes in marine animals: the state of the art.

Glycobiology is the study of complex carbohydrates in biological systems and represents a developing field of science that has made huge advances in the last half century. In fact, it combines all branches of biomedical research, revealing the vast and diverse forms of carbohydrate structures that exist in nature. Advances in structure determination have enabled scientists to study the function of complex carbohydrates in more depth and to determine the role that they play in a wide range of biological processes. Glycobiology research in marine systems has primarily focused on reproduction, in particular for what concern the chemical communication between the gametes. The current status of marine glycobiology is primarily descriptive, devoted to characterizing marine glycoconjugates with potential biomedical and biotechnological applications. In this review, we describe the current status of the glycobiology in the reproductive processes from gametogenesis to fertilization and embryo development of marine animals.

Glicopatología, glicoterapéutica y marcadores tumorales glicánicos / Glicopatology, Glycotherapeutic and Glycan Tumor Markers

La desregulación (por causas genéticas o adquiridas) de la actividad de ciertas glicosiltransferasas, glicosidasas o isomerasas que catalizan los procesos metabólicos en que participan los glicoconjugados - moléculas resultantes de la unión entre glúcidos y prótidos o glúcidos y lípidos - ocasiona anomalías en la estructura química de estos compuestos, por originarse moléculas (generalmente truncadas o con ramificación aberrante) incapaces de efectuar sus funciones biológicas normales. Surgen así anomalías por almacenamiento, provocadas por disfunción o ausencia de la actividad catabólica a cargo de enzimas lisosómicas ("Lysosomal Storage Disorders") o desórdenes congénitos de glicosilación ("Congenital disorders of Glycosylation, CDG") que afectan a la biosíntesis de estas sustancias. La Glicopatología resultante se halla estrechamente vinculada con procesos infecciosos por: virus (gripe, SIDA, etc.), bacterias (E. coli, Streptococcus sp., Helicobacter pylori, etc.), hongos o protozoos, así como con procesos cancerosos o inmunitarios(AU)

The disregulation (due to genetic or acquired factors) of the activity of certain glycosyltransferases, glicosidases or isomerases which catalyse the metabolic processes related to the glycoconjugates - molecules resulting of the link between carbohydrates and proteins or between carbohydrates and lipids - produces anomalies in the chemical structure of these compounds (generally truncated structures or aberrant chain branching) who preclude their normal biological functions. So, Lysosomal Storage Disorders (by abnormalities in the catabolic way) or Congenital Disorders of Glycosylation (by abnormalities in the biosynthetic route) arise. Infectious processes, either by viruses (influenza, AIDS, etc.) or bacteria (E. coli, Streptococcus sp., Helicobacter pylori, etc.) or fungi or protozoa, as well as cancer or immune processes, belong to the chapter of the Glycopathology(AU)

Glycoconjugates in New World species of Leishmania: polymorphisms in lipophosphoglycan and glycoinositolphospholipids and interaction with hosts.

BACKGROUND: Protozoan parasites of the genus Leishmania cause a number of important diseases in humans and undergo a complex life cycle, alternating between a sand fly vector and vertebrate hosts. The parasites have a remarkable capacity to avoid destruction in which surface molecules are determinant for survival. Amongst the many surface molecules of Leishmania, the glycoconjugates are known to play a central role in host-parasite interactions and are the focus of this review. SCOPE OF THE REVIEW: The most abundant and best studied glycoconjugates are the Lipophosphoglycans (LPGs) and glycoinositolphospholipids (GIPLs). This review summarizes the main studies on structure and biological functions of these molecules in New World Leishmania species. MAJOR CONCLUSIONS: LPG and GIPLs are complex molecules that display inter- and intraspecies polymorphisms. They are key elements for survival inside the vector and to modulate the vertebrate immune response during infection. GENERAL SIGNIFICANCE: Most of the studies on glycoconjugates focused on Old World Leishmania species. Here, it is reported some of the studies involving New World species and their biological significance on host-parasite interaction. This article is part of a Special Issue entitled Glycoproteomics.

Structure, functions, and biosynthesis of glycoconjugates of Leishmania spp. cell surface.

Cell surface of leishmaniasis causal agent, a parasitic member of Protozoa of Leishmania genus, is covered by thick glycocalix consisting of various phosphatidylinositol-anchored molecules. This review deals with the structure and biosynthesis of the main phosphoglycans and glycoproteins of Leishmania cell surface, many of which incorporate the rare natural D-arabinopyranose, and the problem concerning the involvement of these molecules in support of Leishmania survival during their intricate life cycle is discussed.

Glycobiology of the Leishmania parasite and emerging targets for antileishmanial drug discovery.

IMPORTANCE OF THE FIELD: Parasitic diseases that pose a threat to human life include leishmaniasis - caused by protozoa of Leishmania species. Existing drugs have limitations due to deleterious side effects like teratogenicity and factors like cost and drug resistance, thus furthering the need to develop this area of research. AREAS COVERED IN THIS REVIEW: We came across drug targets, very recently characterised, cloned and validated by genomics and bioinformatics. We bring these promising drug targets into focus so that they can be explored to their fullest. WHAT THE READER WILL GAIN: In an effort to bridge the gaps between existing knowledge and future prospects of drug discovery, we found interesting studies validating drug targets and paving the way for better experiments to be designed. In a few cases, novel pathways have been characterized, while in others, well established pathways when probed further, led to the discovery of new drug targets. TAKE HOME MESSAGE: The review constitutes a comprehensive report on upcoming drug targets, with emphasis on glycosylphosphatidylinositol (GPI)-anchored glycoconjugates along with related biochemistry of enolase, glycosome and purine salvage pathways, as we strive to bring ourselves a step closer to being able to combat this deadly disease.

Marine glycobiology: current status and future perspectives.

Glycobiology, which is the study of the structure and function of carbohydrates and carbohydrate containing molecules, is fundamental to all biological systems.Progress in glycobiology has shed light on a range of complex biological processes associated with, for example,disease and immunology, molecular and cellular communication,and developmental biology. There is an established,if rather modest, tradition of glycobiology research in marine systems that has primarily focused on reproduction,biofouling, and chemical communication. The current status of marine glycobiology research is primarily descriptive with very limited progress on structural elucidation and the subsequent definition of precise functional roles beyond a small number of classical examples, e.g., induction of the acrosome reaction in echinoderms. However, with recent advances in analytical instrumentation, there is now the capacity to begin to characterize marine glycoconjugates,many of which will have potential biomedical and biotechnological applications. The analytical approach to glycoscience has developed to such an extent that it has acquired its own "-omics" identity. Glycomics is the quest to decipher the complex information conveyed by carbohydrate molecules--the carbohydrate code or glycocode. Due to the paucity of structural information available, this article will highlight the fundamental importance of glycobiology for many biological processes in marine organisms and will draw upon the best defined systems. These systems therefore may prove genuine candidates for full carbohydrate characterization.

Never take candy from a stranger: the role of the bacterial glycome in host-pathogen interactions.

With the comprehensive study and complete sequencing of the Haemophilus influenzae genome in 1995 came the term 'genomics' and the beginning of the 'omics' era. Since this time, several analogous fields, such as transcriptomics and proteomics, have emerged. While growth and advancement in these fields have increased understanding of microbial virulence, the study of bacterial glycomes is still in its infancy and little is known concerning their role in host-pathogen interactions. Bacterial glycomics is challenging owing to the diversity of glyco-conjugate molecules, vast array of unusual sugars and limited number of analytical approaches available. However, recent advances in glycomics technologies offer the potential for exploration and characterization of both the structures and functions of components of bacterial glycomes in a systematic manner. Such characterization is a prerequisite for discerning the role of bacterial glycans in the interaction between host defences and bacterial virulence factors.

Chapter 2: Biogenesis of the cell wall and other glycoconjugates of Mycobacterium tuberculosis.

The re-emergence of tuberculosis in its present-day manifestations - single, multiple and extensive drug-resistant forms and as HIV-TB coinfections - has resulted in renewed research on fundamental questions such as the nature of the organism itself, Mycobacterium tuberculosis, the molecular basis of its pathogenesis, definition of the immunological response in animal models and humans, and development of new intervention strategies such as vaccines and drugs. Foremost among these developments has been the precise chemical definition of the complex and distinctive cell wall of M. tuberculosis, elucidation of the relevant pathways and underlying genetics responsible for the synthesis of the hallmark moieties of the tubercle bacillus such as the mycolic acid-arabinogalactan-peptidoglycan complex, the phthiocerol- and trehalose-containing effector lipids, the phosphatidylinositol-containing mannosides, lipomannosides and lipoarabinomannosides, major immunomodulators, and others. In this review, the laboratory personnel who have been the focal point of some to these developments review recent progress towards a comprehensive understanding of the basic physiology and functions of the cell wall of M. tuberculosis.

Rosetting in Plasmodium falciparum: a cytoadherence phenotype with multiple actors.

The capacity of Plasmodium falciparum-infected red blood cells to bind uninfected red blood cells ("rosetting") has been associated with high parasite density in numerous geographic areas and with severe malaria in African children. We summarize here the associations that have emerged from field studies and describe the various experimental models of rosetting that have been developed. A variety of erythrocyte receptors, several serum factors and a number of rosette-mediating PfEMP1 adhesins have been identified. Several var genes code for rosette-forming PfEMP1 adhesins in each P. falciparum genome, so that each clonal line has the capacity to generate distinct types of rosettes. To clarify their respective role in malaria pathogenesis, each of the multiple ligand/receptor interactions should be further studied for fine specificity, binding affinity and the impact of the large population polymorphism of the parasite variant repertoires should be assessed. Interestingly, some major human erythrocyte surface polymorphisms have been identified as affecting rosette formation, consistent with a role for rosetting in life-threatening falciparum malaria.

Targeting glycoproteins or glycolipids and their metabolic pathways for antiparasite therapy.

Carbohydrate-based therapy, known as glycotherapeutics, is a new and emerging field that promises to be the future hope for combating kinetoplastid infections more efficiently and effectively. Targeting novel glycoproteins/lipids, which are important disease determinants of kinetoplastid diseases, have helped in the development of this field. Better and refined understanding of all the available data would possibly help us in providing a future direction for rational drug design and better disease management. This review intends to focus on such lines, which will give us an insight into the future hope for development of novel therapeutic strategies through glycobiological platform for combating kinetoplastid infections.