title: Thermodynamic Switch in Binding of Adhesion/Growth Regulatory Human Galectin-3 to Tumor-Associated TF Antigen (CD176) and MUC1 Glycopeptides.
abstract: A shift to short-chain glycans is an observed change in mucin-type O-glycosylation in premalignant and malignant epithelia. Given the evidence that human galectin-3 can interact with mucins and also weakly with free tumor-associated Thomsen-Friedenreich (TF) antigen (CD176), the study of its interaction with MUC1 (glyco)peptides is of biomedical relevance. Glycosylated MUC1 fragments that carry the TF antigen attached through either Thr or Ser side chains were synthesized using standard Fmoc-based automated solid-phase peptide chemistry. The dissociation constants (Kd) for interaction of galectin-3 and the glycosylated MUC1 fragments measured by isothermal titration calorimetry decreased up to 10 times in comparison to that of the free TF disaccharide. No binding was observed for the nonglycosylated control version of the MUC1 peptide. The most notable feature of the binding of MUC1 glycopeptides to galectin-3 was a shift from a favorable enthalpy to an entropy-driven binding process. The comparatively diminished enthalpy contribution to the free energy (ΔG) was compensated by a considerable gain in the entropic term. (1)H-(15)N heteronuclear single-quantum coherence spectroscopy nuclear magnetic resonance data reveal contact at the canonical site mainly by the glycan moiety of the MUC1 glycopeptide. Ligand-dependent differences in binding affinities were also confirmed by a novel assay for screening of low-affinity glycan-lectin interactions based on AlphaScreen technology. Another key finding is that the glycosylated MUC1 peptides exhibited activity in a concentration-dependent manner in cell-based assays revealing selectivity among human galectins. Thus, the presentation of this tumor-associated carbohydrate ligand by the natural peptide scaffold enhances its affinity, highlighting the significance of model studies of human lectins with synthetic glycopeptides.
authors.affiliation: †Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science, Florida Atlantic University, 777 Glades Road, Boca Raton, Florida 33431, United States.|‡Torrey Pines Institute for Molecular Studies, 11350 Southwest Village Parkway, Port St. Lucie, Florida 34987, United States.
authors.forename: Maria C
authors.initials: MC
authors.lastname: Rodriguez
authors.affiliation: ‡Torrey Pines Institute for Molecular Studies, 11350 Southwest Village Parkway, Port St. Lucie, Florida 34987, United States.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Yegorova
authors.affiliation: ‡Torrey Pines Institute for Molecular Studies, 11350 Southwest Village Parkway, Port St. Lucie, Florida 34987, United States.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Pitteloud
authors.affiliation: ‡Torrey Pines Institute for Molecular Studies, 11350 Southwest Village Parkway, Port St. Lucie, Florida 34987, United States.
authors.forename: Anais E
authors.initials: AE
authors.lastname: Chavaroche
authors.affiliation: §Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University, Veterinärstrasse 13, 80539 Munich, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: André
authors.affiliation: ∥CIC bioGUNE, Bizkaia Technological Park, Building 801 A, 48160 Derio, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Ardá
authors.affiliation: ‡Torrey Pines Institute for Molecular Studies, 11350 Southwest Village Parkway, Port St. Lucie, Florida 34987, United States.
authors.forename: Dimitriy
authors.initials: D
authors.lastname: Minond
authors.affiliation: ∥CIC bioGUNE, Bizkaia Technological Park, Building 801 A, 48160 Derio, Spain.|⊥Ikerbasque, Basque Foundation for Science, Maria Lopez de Haro 3, 48013 Bilbao, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Jiménez-Barbero
authors.affiliation: §Institute of Physiological Chemistry, Faculty of Veterinary Medicine, Ludwig-Maximilians-University, Veterinärstrasse 13, 80539 Munich, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Gabius
authors.affiliation: †Department of Chemistry and Biochemistry, Charles E. Schmidt College of Science, Florida Atlantic University, 777 Glades Road, Boca Raton, Florida 33431, United States.
authors.forename: Mare
authors.initials: M
authors.lastname: Cudic
mesh_terms: D000818:Animals; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry*; D001667:Binding, Competitive; D016466:CHO Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D003412:Cricetulus; D019277:Entropy; D037502:Galectin 3 / Q000737:chemistry*; D006020:Glycopeptides / Q000737:chemistry*; D006801:Humans; D018396:Mucin-1 / Q000737:chemistry*; D011485:Protein Binding
chemical_list: D015295:Antigens, Tumor-Associated, Carbohydrate; D037502:Galectin 3; D006020:Glycopeptides; C060192:MUC1 protein, human; D018396:Mucin-1; C016467:Thomsen-Friedenreich antigen