title: Multitasking Human Lectin Galectin-3 Interacts with Sulfated Glycosaminoglycans and Chondroitin Sulfate Proteoglycans.
abstract: Glycosaminoglycan (GAG) binding proteins (GAGBPs), including growth factors, cytokines, morphogens, and extracellular matrix proteins, interact with both free GAGs and those covalently linked to proteoglycans. Such interactions modulate a variety of cellular and extracellular events, such as cell growth, metastasis, morphogenesis, neural development, and inflammation. GAGBPs are structurally and evolutionarily unrelated proteins that typically recognize internal sequences of sulfated GAGs. GAGBPs are distinct from the other major group of glycan binding proteins, lectins. The multifunctional human galectin-3 (Gal-3) is a β-galactoside binding lectin that preferentially binds to N-acetyllactosamine moieties on glycoconjugates. Here, we demonstrate through microcalorimetric and spectroscopic data that Gal-3 possesses the characteristics of a GAGBP. Gal-3 interacts with unmodified heparin, chondroitin sulfate-A (CSA), -B (CSB), and -C (CSC) as well as chondroitin sulfate proteoglycans (CSPGs). While heparin, CSA, and CSC bind with micromolar affinity, the affinity of CSPGs is nanomolar. Significantly, CSA, CSC, and a bovine CSPG were engaged in multivalent binding with Gal-3 and formed noncovalent cross-linked complexes with the lectin. Binding of sulfated GAGs was completely abolished when Gal-3 was preincubated with β-lactose. Cross-linking of Gal-3 by CSA, CSC, and the bovine CSPG was reversed by β-lactose. Both observations strongly suggest that GAGs primarily occupy the lactose/LacNAc binding site of Gal-3. Hill plot analysis of calorimetric data reveals that the binding of CSA, CSC, and a bovine CSPG to Gal-3 is associated with progressive negative cooperativity effects. Identification of Gal-3 as a GAGBP should help to reveal new functions of Gal-3 mediated by GAGs and proteoglycans.
authors.affiliation: Laboratory of Mechanistic Glycobiology, Department of Chemistry, ‡Department of Biological Sciences, §Life Science and Technology Institute, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Melanie L
authors.initials: ML
authors.lastname: Talaga
authors.affiliation: Laboratory of Mechanistic Glycobiology, Department of Chemistry, ‡Department of Biological Sciences, §Life Science and Technology Institute, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Ni
authors.initials: N
authors.lastname: Fan
authors.affiliation: Laboratory of Mechanistic Glycobiology, Department of Chemistry, ‡Department of Biological Sciences, §Life Science and Technology Institute, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Ashli L
authors.initials: AL
authors.lastname: Fueri
authors.affiliation: Laboratory of Mechanistic Glycobiology, Department of Chemistry, ‡Department of Biological Sciences, §Life Science and Technology Institute, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Brown
authors.affiliation: Laboratory of Mechanistic Glycobiology, Department of Chemistry, ‡Department of Biological Sciences, §Life Science and Technology Institute, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Purnima
authors.initials: P
authors.lastname: Bandyopadhyay
authors.affiliation: Laboratory of Mechanistic Glycobiology, Department of Chemistry, ‡Department of Biological Sciences, §Life Science and Technology Institute, Michigan Technological University , Houghton, Michigan 49931, United States.
authors.forename: Tarun K
authors.initials: TK
authors.lastname: Dam
mesh_terms: D000606:Amino Sugars / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D011508:Chondroitin Sulfate Proteoglycans / Q000378:metabolism*; D003871:Dermatan Sulfate / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D037502:Galectin 3 / Q000737:chemistry / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007785:Lactose / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D000606:Amino Sugars; D011508:Chondroitin Sulfate Proteoglycans; D037502:Galectin 3; D006025:Glycosaminoglycans; C032233:lactosamine; D003871:Dermatan Sulfate; D012965:Sodium Chloride; D006493:Heparin; D007785:Lactose