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Impact of sialic acids on the molecular dynamic of bi-antennary and tri-antennary glycans. Sci Rep 2016; 6:35666. [PMID: 27759083 PMCID: PMC5069492 DOI: 10.1038/srep35666] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 10/03/2016] [Indexed: 01/12/2023] Open
Abstract
Sialic acids (SA) are monosaccharides that can be located at the terminal position of glycan chains on a wide range of proteins. The post-translational modifications, such as N-glycan chains, are fundamental to protein functions. Indeed, the hydrolysis of SA by specific enzymes such as neuraminidases can lead to drastic modifications of protein behavior. However, the relationship between desialylation of N-glycan chains and possible alterations of receptor function remains unexplored. Thus, the aim of the present study is to establish the impact of SA removal from N-glycan chains on their conformational behavior. We therefore undertook an in silico investigation using molecular dynamics to predict the structure of an isolated glycan chain. We performed, for the first time, 3 independent 500 ns simulations on bi-antennary and tri-antennary glycan chains displaying or lacking SA. We show that desialylation alters both the preferential conformation and the flexibility of the glycan chain. This study suggests that the behavior of glycan chains induced by presence or absence of SA may explain the changes in the protein function.
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Tecle E, Gagneux P. Sugar-coated sperm: Unraveling the functions of the mammalian sperm glycocalyx. Mol Reprod Dev 2015; 82:635-50. [PMID: 26061344 PMCID: PMC4744710 DOI: 10.1002/mrd.22500] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Accepted: 04/30/2015] [Indexed: 01/05/2023]
Abstract
Mammalian spermatozoa are coated with a thick glycocalyx that is assembled during sperm development, maturation, and upon contact with seminal fluid. The sperm glycocalyx is critical for sperm survival in the female reproductive tract and is modified during capacitation. The complex interplay among the various glycoconjugates generates numerous signaling motifs that may regulate sperm function and, as a result, fertility. Nascent spermatozoa assemble their own glycans while the cells still possess a functional endoplasmic reticulum and Golgi in the seminiferous tubule, but once spermatogenesis is complete, they lose the capacity to produce glycoconjugates de novo. Sperm glycans continue to be modified, during epididymal transit by extracellular glycosidases and glycosyltransferases. Furthermore, epididymal cells secrete glycoconjugates (glycophosphatidylinositol-anchored glycoproteins and glycolipids) and glycan-rich microvesicles that can fuse with the maturing sperm membrane. The sperm glycocalyx mediates numerous functions in the female reproductive tract, including the following: inhibition of premature capacitation; passage through the cervical mucus; protection from innate and adaptive female immunity; formation of the sperm reservoir; and masking sperm proteins involved in fertilization. The immense diversity in sperm-associated glycans within and between species forms a remarkable challenge to our understanding of essential sperm glycan functions.
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Affiliation(s)
- Eillen Tecle
- Division of Comparative Pathology and Medicine, Department of Pathology, Glycobiology Research and Training Center, University of California San Diego, La Jolla, California
| | - Pascal Gagneux
- Division of Comparative Pathology and Medicine, Department of Pathology, Glycobiology Research and Training Center, University of California San Diego, La Jolla, California
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Au CE, Hermo L, Byrne E, Smirle J, Fazel A, Simon PHG, Kearney RE, Cameron PH, Smith CE, Vali H, Fernandez-Rodriguez J, Ma K, Nilsson T, Bergeron JJM. Expression, sorting, and segregation of Golgi proteins during germ cell differentiation in the testis. Mol Biol Cell 2015; 26:4015-32. [PMID: 25808494 PMCID: PMC4710233 DOI: 10.1091/mbc.e14-12-1632] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/19/2015] [Indexed: 12/14/2022] Open
Abstract
A total of 1318 proteins characterized in the male germ cell Golgi apparatus reveal a new germ cell–specific Golgi marker and a new pan-Golgi marker for all cells. The localization of these and other Golgi proteins reveals differential expression linked to mitosis, meiosis, acrosome formation, and postacrosome Golgi migration and destination in the late spermatid. The molecular basis of changes in structure, cellular location, and function of the Golgi apparatus during male germ cell differentiation is unknown. To deduce cognate Golgi proteins, we isolated germ cell Golgi fractions, and 1318 proteins were characterized, with 20 localized in situ. The most abundant protein, GL54D of unknown function, is characterized as a germ cell–specific Golgi-localized type II integral membrane glycoprotein. TM9SF3, also of unknown function, was revealed to be a universal Golgi marker for both somatic and germ cells. During acrosome formation, several Golgi proteins (GBF1, GPP34, GRASP55) localize to both the acrosome and Golgi, while GL54D, TM9SF3, and the Golgi trafficking protein TMED7/p27 are segregated from the acrosome. After acrosome formation, GL54D, TM9SF3, TMED4/p25, and TMED7/p27 continue to mark Golgi identity as it migrates away from the acrosome, while the others (GBF1, GPP34, GRASP55) remain in the acrosome and are progressively lost in later steps of differentiation. Cytoplasmic HSP70.2 and the endoplasmic reticulum luminal protein-folding enzyme PDILT are also Golgi recruited but only during acrosome formation. This resource identifies abundant Golgi proteins that are expressed differentially during mitosis, meiosis, and postacrosome Golgi migration, including the last step of differentiation.
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Affiliation(s)
- Catherine E Au
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - Louis Hermo
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada
| | - Elliot Byrne
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - Jeffrey Smirle
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - Ali Fazel
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - Paul H G Simon
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - Robert E Kearney
- Department of Biomedical Engineering Department, McGill University, Montreal, QC H3A 2B4, Canada
| | - Pamela H Cameron
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - Charles E Smith
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada
| | - Hojatollah Vali
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada
| | - Julia Fernandez-Rodriguez
- Centre for Cellular Imaging, Sahlgrenska Academy, University of Gothenburg, 405 30 Gothenburg, Sweden
| | - Kewei Ma
- Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - Tommy Nilsson
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
| | - John J M Bergeron
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC H3A 0C7, Canada Division of Endocrinology and Metabolism, McGill University Health Centre Research Institute, Montreal, QC H3A 1A1, Canada
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Valbuena G, Madrid JF, Martínez de Ubago M, Gómez-Santos L, Alonso E, Díaz-Flores L, Sáez FJ. N-Glycans in Xenopus laevis testis characterised by lectin histochemistry. Reprod Fertil Dev 2014; 28:337-48. [PMID: 25482090 DOI: 10.1071/rd14077] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 06/03/2014] [Indexed: 11/23/2022] Open
Abstract
Analysis of glycan chains of glycoconjugates is difficult because of their considerable variety. Despite this, several functional roles for these glycans have been reported. N-Glycans are oligosaccharides linked to asparagine residues of proteins. They are synthesised in the endoplasmic reticulum (ER) in a unique way, and later modified in both the ER and Golgi apparatus, developing different oligosaccharide chains. An essential role for complex N-glycans in mammalian spermatogenesis has been reported. The aim of the present study was to analyse the N-glycans of the Xenopus laevis testis by means of lectin histochemistry. Five lectins were used that specifically recognise mannose-containing and complex glycans, namely Galanthus nivalis agglutinin (GNA) from snowdrops, concanavalin A (Con A) from the Jack bean, Lens culinaris agglutinin (LCA) from lentils and Phaseolus vulgaris erythroagglutinin (PHA-E) and P. vulgaris leukoagglutinin (PHA-L) from the common bean. GNA and Con A labelled the interstitium and most of the germ cell types, whereas LCA and PHA-E showed affinity only for the interstitium. A granular cytoplasmic region was labelled in spermatogonia and spermatocytes by GNA and PHA-L, whereas GNA and LCA labelled a spermatid region that is probably associated with the centriolar basal body of the nascent flagellum. There was no specific labelling in the acrosome. Some unexpected results were found when deglycosylative pretreatments were used: pre-incubation of tissue sections with peptide N glycosidase F, which removes N-linked glycans, reduced or removed labelling with most lectins, as expected. However, after this pretreatment, the intensity of labelling remained or increased for Con A in the follicle (Sertoli) and post-meiotic germ cells. The β-elimination procedure, which removes O-linked glycans, revealed new labelling patterns with GNA, LCA and PHA-L, suggesting that some N-glycans were masked by O-glycans, and thus they became accessible to these lectins only after removal of the O-linked oligosaccharides. The functional role of the glycan chains identified could be related to the role of N-glycans involved in mammalian spermatogenesis reported previously.
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Affiliation(s)
- Galder Valbuena
- Department of Cell Biology and Histology, School of Medicine and Dentistry, University of the Basque Country UPV/EHU, B° Sarriena s/n, E-48940 Leioa, Vizcaya, Spain
| | - Juan Francisco Madrid
- Department of Cell Biology and Histology, School of Medicine, Regional Campus of International Excellence 'Campus Mare Nostrum', University of Murcia, E-30100 Espinardo, Murcia, Spain
| | - María Martínez de Ubago
- Department of Cell Biology and Histology, School of Medicine and Dentistry, University of the Basque Country UPV/EHU, B° Sarriena s/n, E-48940 Leioa, Vizcaya, Spain
| | - Laura Gómez-Santos
- Department of Cell Biology and Histology, School of Medicine and Dentistry, University of the Basque Country UPV/EHU, B° Sarriena s/n, E-48940 Leioa, Vizcaya, Spain
| | - Edurne Alonso
- Department of Cell Biology and Histology, School of Medicine and Dentistry, University of the Basque Country UPV/EHU, B° Sarriena s/n, E-48940 Leioa, Vizcaya, Spain
| | - Lucio Díaz-Flores
- Department of Anatomy, Pathology, Histology and Radiology, University of La Laguna, Ofra-La Cuesta s/n, La Laguna, E-38071 Tenerife, Spain
| | - Francisco J Sáez
- Department of Cell Biology and Histology, School of Medicine and Dentistry, University of the Basque Country UPV/EHU, B° Sarriena s/n, E-48940 Leioa, Vizcaya, Spain
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Bi J, Li Y, Sun F, Saalbach A, Klein C, Miller DJ, Hess R, Nowak RA. Basigin null mutant male mice are sterile and exhibit impaired interactions between germ cells and Sertoli cells. Dev Biol 2013; 380:145-56. [PMID: 23727514 DOI: 10.1016/j.ydbio.2013.05.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 05/10/2013] [Accepted: 05/14/2013] [Indexed: 11/18/2022]
Abstract
Basigin (BSG) is a multifunctional glycoprotein that plays an important role in male reproduction since male knockout (KO) mice are sterile. The Bsg KO testis lacks elongated spermatids and mature spermatozoa, a phenotype similar to that of alpha-mannosidase IIx (MX) KO mice. MX regulates formation of N-acetylglucosamine (GlcNAc) terminated N-glycans that participate in germ cell-Sertoli cell adhesion. Results showed that Bsg KO spermatocytes displayed normal homologous chromosome synapsis and progression through meiosis. However, only punctate expression of the round spermatid marker SP-10 in the acrosomal granule of germ cells of Bsg KO mice was detected indicating that spermatogenesis in Bsg KO mice was arrested at the early round spermatid stages. We observed a large increase in the number of germ cells undergoing apoptosis in Bsg KO testes. Using lectin blotting, we determined that GlcNAc terminated N-glycans are linked to BSG. GlcNAc terminated N-glycans were significantly reduced in Bsg KO testes. These observations indicate that BSG may act as a germ cell-Sertoli cell attachment molecule. Loss of BSG significantly reduced adhesion between GC-2 and SF7 cells. Moreover, wild type testes showed strong expression of N-cadherin (CDH2) while expression was greatly reduced in the testes of Bsg KO mice. In addition, the integrity of the blood-testis barrier (BTB) was compromised in Bsg KO testes. In conclusion, although some Bsg KO spermatogonia can undergo normal progression to the spermatocyte stage, BSG-mediated germ cell-Sertoli cell interactions appear to be necessary for integrity of the BTB and spermatocyte progression to mature spermatozoa.
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Affiliation(s)
- Jiajia Bi
- Department of Animal Sciences, University of Illinois, Urbana, IL, USA
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Azzouz N, Kamena F, Seeberger PH. Synthetic Glycosylphosphatidylinositol as Tools for Glycoparasitology Research. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2010; 14:445-54. [DOI: 10.1089/omi.2009.0138] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Nahid Azzouz
- Max Planck Institute of Colloids and Interfaces, Department of Biomolecular Systems, Research Campus, Golm, Germany, and Free University Berlin, Berlin, Germany
| | - Faustin Kamena
- Max Planck Institute of Colloids and Interfaces, Department of Biomolecular Systems, Research Campus, Golm, Germany, and Free University Berlin, Berlin, Germany
| | - Peter H. Seeberger
- Max Planck Institute of Colloids and Interfaces, Department of Biomolecular Systems, Research Campus, Golm, Germany, and Free University Berlin, Berlin, Germany
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Wong WC, Loh M, Eisenhaber F. On the necessity of different statistical treatment for Illumina BeadChip and Affymetrix GeneChip data and its significance for biological interpretation. Biol Direct 2008; 3:23. [PMID: 18522715 PMCID: PMC2453111 DOI: 10.1186/1745-6150-3-23] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Accepted: 06/03/2008] [Indexed: 11/25/2022] Open
Abstract
Background The original spotted array technology with competitive hybridization of two experimental samples and measuring relative expression levels is increasingly displaced by more accurate platforms that allow determining absolute expression values for a single sample (for example, Affymetrix GeneChip and Illumina BeadChip). Unfortunately, cross-platform comparisons show a disappointingly low concordance between lists of regulated genes between the latter two platforms. Results Whereas expression values determined with a single Affymetrix GeneChip represent single measurements, the expression results obtained with Illumina BeadChip are essentially statistical means from several dozens of identical probes. In the case of multiple technical replicates, the data require, therefore, different stistical treatment depending on the platform. The key is the computation of the squared standard deviation within replicates in the case of the Illumina data as weighted mean of the square of the standard deviations of the individual experiments. With an Illumina spike experiment, we demonstrate dramatically improved significance of spiked genes over all relevant concentration ranges. The re-evaluation of two published Illumina datasets (membrane type-1 matrix metalloproteinase expression in mammary epithelial cells by Golubkov et al. Cancer Research (2006) 66, 10460; spermatogenesis in normal and teratozoospermic men, Platts et al. Human Molecular Genetics (2007) 16, 763) significantly identified more biologically relevant genes as transcriptionally regulated targets and, thus, additional biological pathways involved. Conclusion The results in this work show that it is important to process Illumina BeadChip data in a modified statistical procedure and to compute the standard deviation in experiments with technical replicates from the standard errors of individual BeadChips. This change leads also to an improved concordance with Affymetrix GeneChip results as the spermatogenesis dataset re-evaluation demonstrates. Reviewers This article was reviewed by I. King Jordan, Mark J. Dunning and Shamil Sunyaev.
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Affiliation(s)
- Wing-Cheong Wong
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street #07-01, Matrix Building, 138671, Singapore.
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Huyghe E, Nohra J, Vezzosi D, Bennet A, Caron P, Mieusset R, Bujan L, Plante P. Contraceptions masculines non déférentielles : revue de la littérature. Prog Urol 2007; 17:156-64. [PMID: 17489310 DOI: 10.1016/s1166-7087(07)92254-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
OBJECTIVES To review the state of progress of the various male contraceptive methods (with the exception of deferential methods). MATERIAL AND METHODS A review of the literature was performed by using the key words: male/contraception, limiting the search to original articles in English and French. Articles on vasectomy and the other deferential methods of contraception are not considered in the present review. RESULTS Three methods of male contraception are widely used at the present time: withdrawal, male condom and vasectomy, although other types of male contraception have been shown to be effective, including hormonal contraception, which appears to be the most promising technique and the subject of the majority of research. Other contraceptive methods (immunological, thermal...) could constitute possible alternatives. CONCLUSION Male contraception remains under-used, as only male condoms are commonly used (apart from withdrawal and vasectomy). Consequently, new research protocols in the field of male contraception must be strongly encouraged.
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Affiliation(s)
- Eric Huyghe
- Service d'Urologie et Andrologie, Hôpital Paule de Viguier, Toulouse, France.
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Tokalov SV, Gutzeit HO. Lectin-binding pattern as tool to identify and enrich specific primary testis cells of the tilapia (Oreochromis niloticus) and medaka (Oryzias latipes). JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2007; 308:127-38. [PMID: 16788897 DOI: 10.1002/jez.b.21117] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cell type-specific lectin binding is a useful tool for the analysis of developing systems. We describe the binding pattern of 21 different fluorescein isothiocyanate (FITC)-labelled lectins to the testis of two model teleost species, the medaka (Oryzias latipes) and the tilapia (Oreochromis niloticus). The analysis of the binding pattern was carried out on tissue sections (medaka and tilapia) and using primary culture cells (only tilapia). Lectin binding was studied by confocal microscopy and for histological analysis some sections were, in addition, stained with bodipy to gain additional information concerning the cytological organization of the cystic mode of spermatogenesis in fish. The observed differences in lectin staining of different cell types in primary cultures were quantified by flow cytometry. Only few lectins bound specifically to haploid cells while the reaction to diploid or tetraploid cells was generally stronger. However, the extracellular material around the haploid spermatids and spermatozoa in spermatocysts showed a strong staining reaction with several lectins (e.g., Phaseolus vulgaris Erythro agglutinin). The apparent differences in the cellular lectin-binding pattern can be used to identify particular cell types, to monitor their differentiation in vitro or to enrich particular cell types from heterogeneous cultures using magnetic beads coated with anti-FITC antibodies. Using the latter approach, we show that it is possible to enrich for gonial cells and at the same time deplete the preparation for haploid cells and Sertoli cells.
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Buzás EI, György B, Pásztói M, Jelinek I, Falus A, Gabius HJ. Carbohydrate recognition systems in autoimmunity. Autoimmunity 2007; 39:691-704. [PMID: 17178566 DOI: 10.1080/08916930601061470] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The immune system is a complex functional network of diverse cells and soluble molecules orchestrating innate and adaptive immunity. Biological information, to run these intricate interactions, is not only stored in protein sequences but also in the structure of the glycan part of the glycoconjugates. The spatially accessible carbohydrate structures that contribute to the cell's glycome are decoded by versatile recognition systems in order to maintain the immune homeostasis of an organism. Microbial carbohydrate structures are recognized by pathogen associated molecular pattern (PAMP) receptors of innate immunity including C-type lectins such as MBL, the tandem-repeat-type macrophage mannose receptor, DC-SIGN or dectin-1 of dendritic cells, certain TLRS or the TCR of NKT cells. Natural autoantibodies, a long known effector branch of this network-based operation, are effective to home in on non-self and self-glycosylation also. The recirculating pool of mammalian immune cells is recruited to inflammatory sites by a reaction pathway involving the self-carbohydrate-binding selectins as initial recognition step. Galectins, further key sensors reading the high-density sugar code, exert regulatory functions on activated T cells, among other activities. Autoimmune diseases are being associated with defined changes of glycosylation. This correlation deserves to be thoroughly studied on the levels of structural mimicry and dysregulation as well as effector molecules to devise innovative anti-inflammatory strategies. This review briefly summarizes data on sensor systems for carbohydrate epitopes and implications for autoimmunity.
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Affiliation(s)
- Edit I Buzás
- Department of Genetics, Cell- and Immunobiology, Semmelweis University, Budapest, Hungary.
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Siebert HC, Rosen J, Seyrek K, Kaltner H, André S, Bovin NV, Nyholm PG, Sinowatz F, Gabius HJ. α2,3/α2,6-Sialylation of N-glycans: non-synonymous signals with marked developmental regulation in bovine reproductive tracts. Biochimie 2006; 88:399-410. [PMID: 16360259 DOI: 10.1016/j.biochi.2005.09.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2005] [Accepted: 09/23/2005] [Indexed: 10/25/2022]
Abstract
The glycan part endows cellular glycoconjugates with significant potential for biological recognition. N-Glycan branches often end with alpha2,3/alpha2,6-sialylation, posing the question whether and how placement of the sialic acid at 3 - or 6 -acceptor positions of galactose has cell biological relevance. As attractive model to study developmental regulation we monitored the expression of alpha2,3/alpha2,6-sialylated determinants in fetal and adult bovine testes and ovaries by lectin histochemistry. Distinct expression patterns were detected in both organ types. Oocyte staining, as a prominent example, was restricted to the presence of alpha2,6-sialylated glycans. Treatment with sialidase abolished binding and thus excluded sulfate esters as lectin targets. We added computer simulations to rationalize the observed evidence for non-random expression of the two closely related sialylgalactose isomers. Extensive molecular mechanics and molecular dynamics calculations reveal that the seemingly minor shift of the glycosidic bond from the alpha2,3 position to the alpha2,6 configuration causes significant shape and flexibility changes. They give each disaccharide its own characteristic meaning as signal in the sugar code.
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Affiliation(s)
- Hans-Christian Siebert
- Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University, Veterinärstr. 13, 80539 München, Germany
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Abstract
Obtaining a better understanding of the molecular basis of cell recognition remains an important challenge with regard to the social functioning of cells in multicellular systems. The wide structural diversity of carbohydrates allows many combinatorial possibilities for fine-tuning cell-cell and cell-matrix recognition in multicellular organisms. Direct carbohydrate-carbohydrate interaction would endow both the flexibility and the specificity of reversible contacts at the cell surface during the formation, maintenance and pathogenesis of tissues. The recent development of methods for the characterization of such interactions will help to expand our knowledge of the mechanisms that trigger early events in cell recognition.
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Affiliation(s)
- Iwona Bucior
- Friedrich Miescher Institute, Novartis Research Foundation, Maulbeerstrasse 66, 4058 Basel, Switzerland
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