The lectin domains of polypeptide GalNAc-transferases exhibit carbohydrate-binding specificity for GalNAc: lectin binding to GalNAc-glycopeptide substrates is required for high density GalNAc-O-glycosylation

Wandall, Hans H.; Irazoqui, Fernando J.; Tarp, Mads A.; Bennett, Eric; Mandel, Ulla; Takeuchi, Hideyuki; Kato, Kentaro; Irimura, Tatsuro; Suryanarayanan, Ganesh; Hollingsworth, Michael A.; Clausen, Henrik

doi:10.1093/glycob/cwl082

Cited by 95 publications

(107 citation statements)

References 34 publications

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“…3, G-I). Although the effect of the T171G mutation may seem surprising, in other work we observed that T3 requires glycosylation at Thr 171 to glycosylate Thr 178 in a process dependent on the T3 lectin domain 3 (9), similar to the situation for several other GalNActransferase isoforms and their substrates (28,29). More relevant to the present work, the fold-increase for these constructs (Fig.…”

Section: T2 Sensorsupporting

confidence: 82%

Development of Isoform-specific Sensors of Polypeptide GalNAc-transferase Activity

Song

Bachert

Schjoldager

et al. 2014

Journal of Biological Chemistry

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Background:No available inhibitors target isoforms of the biologically and medically relevant enzyme that initiates mucintype O-glycosylation. Results: Protein-based, fluorescent sensors were developed for T2 and T3 isoforms using modified GalNAc-transferase target sites and these were specifically activated in HEK cells lacking their corresponding GalNAc-transferases. Conclusion: The fluorescence sensors are isoform specific. Significance: The designed biosensors may enable high-throughput screening for specific regulators with therapeutic potential.

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Section: T2 Sensorsupporting

confidence: 82%

Development of Isoform-specific Sensors of Polypeptide GalNAc-transferase Activity

Song

Bachert

Schjoldager

et al. 2014

Journal of Biological Chemistry

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“…S1 in the supplementary material). Members of the GalNAc-transferase family are characterised by an N-terminal transmembrane domain that retains the enzyme in the Golgi compartment, a central catalytic domain and a C-terminal Ricin domain that facilitates binding to partially glycosylated substrates Wandall et al, 2007). The N-terminal transmembrane and the central catalytic domain are highly conserved between Xenopus and human Galntl-1 homologues (>80%), whereas the C-terminal Ricin domains are more divergent, with only 40% amino acid identity.…”

Section: Resultsmentioning

confidence: 99%

Regulation of TGF-β signalling by N-acetylgalactosaminyltransferase-like 1

et al. 2008

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The TGF-β superfamily of secreted signalling molecules plays a pivotal role in the regulation of early embryogenesis, organogenesis and adult tissue homeostasis. Here we report the identification of Xenopus N-acetylgalactosaminyltransferase-like 1 (xGalntl-1) as a novel important regulator of TGF-β signalling. N-acetylgalactosaminyltransferases mediate the first step of mucin-type glycosylation, adding N-acetylgalactose to serine or threonine side chains. xGalntl-1 is expressed in the anterior mesoderm and neural crest territory at neurula stage, and in the anterior neural crest, notochord and the mediolateral spinal cord at tailbud stage. Inhibition of endogenous xGalntl-1 protein synthesis, using specific morpholino oligomers, interfered with the formation of anterior neural crest, anterior notochord and the spinal cord. Xenopus and mammalian Galntl-1 inhibited Activin as well as BMP signalling in the early Xenopus embryo and in human HEK 293T cells. Gain-and loss-of-function experiments showed that xGalntl-1 interferes with the activity of the common TGF-β type II receptor ActR-IIB in vivo. In addition, our biochemical data demonstrated that xGalntl-1 specifically interferes with the binding of ActR-IIB to Activin-and BMP-specific type I receptors. This inhibitory activity of xGalntl-1 was dependent on mucin-type glycosylation, as it was sensitive to the chemical inhibitor benzyl-GalNAc. These studies reveal an important role of a N-acetylgalactosaminyltransferase in the regulation of TGF-β signalling. This novel regulatory mechanism is evolutionarily conserved and, thus, might provide a new paradigm for the regulation of TGF-β signalling in vertebrates.

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“…There also exists a smaller subpopulation of IgA1 O-glycoforms that does not follow this semiordered carbohydrate addition, giving rise to differentially O-glycosylated isobaric species. Wandall et al (41) reported that the lectin domains of different GalNAc-transferases can recognize the same substrate. This could result in different sites or order of GalNAc attachment catalyzed by several GalNAc-transferases.…”

Section: Discussionmentioning

confidence: 99%

Clustered O-Glycans of IgA1

Takahashi

Wall

Suzuki

et al. 2010

Molecular & Cellular Proteomics

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Glycosylation is one of the most common post-translational modifications of proteins. It is estimated that over half of mammalian proteins are glycosylated. Patients with several autoimmune disorders, chronic inflammatory diseases, and some infectious diseases exhibit abnormal glycosylation of serum immunoglobulins and other glycoproteins (1-5). The biological functions of these modifications in health and disease have become a significant area of interest in biomedical research (6). A subset of these glycoproteins has clustered sites of O-glycosylation with serine-and threonine-rich stretches within the amino acid sequence. Mucins, such as membrane-associated MUC1, are perhaps the best known family of proteins that are heavily O-glycosylated. Their altered expression and aberrant glycosylation have made them potential targets as biomarkers for early detection of cancer (7). Immunoglobulin A1 (IgA1) 1 contains both O-and N-glycans (Fig. 1). Aberrant O-glycosylation of IgA1 is involved in the pathogenesis of IgA nephropathy (IgAN) and the closely related Henoch-Schö nlein purpura nephritis (1, 8). Interestingly, the aberrantly glycosylated molecules, IgA1 in IgAN and MUC1 in cancer, are recognized by the immune system as neoepitopes as evidenced by formation of specific antibodies (9 -11). Mucin-like bacterial surface proteins exhibit similar properties: the molecules have clustered bacterial O-glycans that mediate cellular adhesion, and blocking antibodies target these glycan-containing epitopes (12).An O-glycosylated protein from a single source contains a population of variably O-glycosylated isoforms that show a distinct distribution of microheterogeneity of the O-glycan chains in terms of number, sites of attachment, and composition. Characterizing these clustered sites and understanding how the distributions change under different biological conditions or disease states are an analytical challenge. Enzymatic or chemical release of O-glycans is not selective. The heterogeneity, composition, and quantitative aspects of different O-glycan chains can be assessed and quantified by gas chromatographic and/or mass spectrometric techniques.

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The lectin domains of polypeptide GalNAc-transferases exhibit carbohydrate-binding specificity for GalNAc: lectin binding to GalNAc-glycopeptide substrates is required for high density GalNAc-O-glycosylation

Cited by 95 publications

References 34 publications

Development of Isoform-specific Sensors of Polypeptide GalNAc-transferase Activity

Development of Isoform-specific Sensors of Polypeptide GalNAc-transferase Activity

Regulation of TGF-β signalling by N-acetylgalactosaminyltransferase-like 1

Clustered O-Glycans of IgA1

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