Mucin‐Type Glycopeptide Structure in Solution: Past, Present, and Future

Barchi, Joseph J.

doi:10.1002/bip.22313

Cited by 25 publications

(20 citation statements)

References 89 publications

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“…This is perhaps not surprising in light of the different conformational preferences for serine- and threonine-linked glycopeptides (vide supra): Rotation about the glycosidic torsion angles in both the Tn antigen (simple α-GalNAc) and the TF ag -linked glycoaminoacids/glycopeptides are much more restricted relative to the same serine-derived conjugates. 80 This may lead to more facile attachment of the more accommodating serine conjugates, while steric considerations may restrict the number of ligands that can be attached with the threonine conjugates. We have also prepared similar particles with doping of the hydroxyl-terminated linker moiety and see more consistent coating on these particles (Barchi and Biswas, unpublished data).…”

Section: Discussionmentioning

confidence: 99%

Synthesis and cell-selective antitumor properties of amino acid conjugated tumor-associated carbohydrate antigen-coated gold nanoparticles

Biswas

Medina

Barchi

2015

Carbohydrate Research

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The Thomsen Friedenreich antigen (TFag) disaccharide is a tumor-associated carbohydrate antigen (TACA) found primarily on carcinoma cells and rarely expressed in normal tissue. The TFag has been shown to interact with Galectin-3 (Gal-3), one in a family of β-galactoside binding proteins. Galectins have a variety of cellular functions, and Gal-3 has been shown to be the solegalectin with anti-apoptotic activity. We have previously prepared gold nanoparticles (AuNP) coated with the TFag in various presentations as potential anti-adhesive therapeutic tools or antitumor vaccine platforms. Here we describe the synthesis of TFag-glycoamino acid conjugates attached to gold nanoparticles through a combined alkane/PEG linker, where the TFag was attached to either a serine or threonine amino acid. Particles were fully characterized by a host of biophysical techniques, and along with a control particle carrying hydroxyl-terminated linker units, were evaluated in both Gal-3 positive and negative cell lines. We show that the particles bearing the saccharides selectively inhibited tumor cell growth of the Gal-3 positive cells significantly more than the Gal-3 negative cells. In addition, the threonine-attached TF particles were more potent than the serine-attached constructs. These results support the use of AuNP as antitumor therapeutic platforms, targeted against cell lines that express specific lectins that interact with TFag.

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Section: Discussionmentioning

confidence: 99%

Synthesis and cell-selective antitumor properties of amino acid conjugated tumor-associated carbohydrate antigen-coated gold nanoparticles

Biswas

Medina

Barchi

2015

Carbohydrate Research

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“…Notable examples at the peptide level include effects of single sugars and neutral glycans on mucin domains, 47−49 and β-linked GlcNAc on an estrogen receptor peptide. 50 In another peptide, O-glycosylation can affect the trans : cis rotamer ratio of nearby Pro residues, 51 and at the protein level, N -glycans affect dimerization of the FGF receptor.…”

Section: Discussionmentioning

confidence: 99%

Glycosylation of Skp1 Affects Its Conformation and Promotes Binding to a Model F-Box Protein

et al. 2014

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In the social amoeba Dictyostelium, Skp1 is hydroxylated on proline 143 and further modified by three cytosolic glycosyltransferases to yield an O-linked pentasaccharide that contributes to O2 regulation of development. Skp1 is an adapter in the Skp1/cullin1/F-box protein family of E3 ubiquitin ligases that targets specific proteins for polyubiquitination and subsequent proteasomal degradation. To investigate the biochemical consequences of glycosylation, untagged full-length Skp1 and several of its posttranslationally modified isoforms were expressed and purified to near homogeneity using recombinant and in vitro strategies. Interaction studies with the soluble mammalian F-box protein Fbs1/Fbg1/OCP1 revealed preferential binding to the glycosylated isoforms of Skp1. This difference correlated with the increased α-helical and decreased β-sheet content of glycosylated Skp1s based on circular dichroism and increased folding order based on small-angle X-ray scattering. A comparison of the molecular envelopes of fully glycosylated Skp1 and the apoprotein indicated that both isoforms exist as an antiparallel dimer that is more compact and extended in the glycosylated state. Analytical gel filtration and chemical cross-linking studies showed a growing tendency of less modified isoforms to dimerize. Considering that regions of free Skp1 are intrinsically disordered and Skp1 can adopt distinct folds when bound to F-box proteins, we propose that glycosylation, which occurs adjacent to the F-box binding site, influences the spectrum of energetically similar conformations that vary inversely in their propensity to dock with Fbs1 or another Skp1. Glycosylation may thus influence Skp1 function by modulating F-box protein binding in cells.

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“…This form of dense mucin-type glycosylation is thought to confer lubricating properties, 63 extend the polypeptide backbone, reduce flexibility, and provide resistance to proteases. 7,64 For example, O-glycans are thought to extend GP1BA from the platelet surface, allowing optimal interaction with VWF under shear stress. 21 The presence of a mucin-type domain in the soluble coagulation factors could conceivably protect the factors from degradation and premature activation in circulation, but such a role has not yet been described.…”

Section: Discussionmentioning

confidence: 99%

Characterizing the O-glycosylation landscape of human plasma, platelets, and endothelial cells

et al. 2017

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Key Points• Human platelets, endothelial cells, and plasma proteins are extensively O-glycosylated, with .1123 O-glycosites identified in this study.• O-glycosites can be classified into functional subgroups; one important function includes the protection from proteolytic processing.The hemostatic system comprises platelet aggregation, coagulation, and fibrinolysis, and is critical to the maintenance of vascular integrity. Multiple studies indicate that glycans play important roles in the hemostatic system; however, most investigations have focused on Using an unbiased screen to identify associations between O-glycosites and protein annotations we found that O-glycans were over-represented close (6 15 amino acids) to tandem repeat regions, protease cleavage sites, within propeptides, and located on a select group of protein domains. The importance of O-glycosites in proximity to proteolytic cleavage sites was further supported by in vitro peptide assays demonstrating that proteolysis of key hemostatic proteins can be inhibited by the presence of O-glycans.Collectively, these data illustrate the global properties of native O-glycosylation and provide the requisite roadmap for future biomarker and structure-function studies.

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Mucin‐Type Glycopeptide Structure in Solution: Past, Present, and Future

Cited by 25 publications

References 89 publications

Synthesis and cell-selective antitumor properties of amino acid conjugated tumor-associated carbohydrate antigen-coated gold nanoparticles

Synthesis and cell-selective antitumor properties of amino acid conjugated tumor-associated carbohydrate antigen-coated gold nanoparticles

Glycosylation of Skp1 Affects Its Conformation and Promotes Binding to a Model F-Box Protein

Characterizing the O-glycosylation landscape of human plasma, platelets, and endothelial cells

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