title: Cell surface proteoglycans syndecan-1 and -4 bind overlapping but distinct sites in laminin α3 LG45 protein domain.
abstract: Keratinocyte migration during epidermal repair depends on interactions between cellular heparan sulfate proteoglycan receptors, syndecan-1 and -4, and the C-terminal globular domains (LG45) of the extracellular matrix protein laminin 332. This study investigates the molecular basis of the binding specificity of the syndecan-1 and -4 receptors expressed by human keratinocytes. We used site-directed mutagenesis to alter a recombinant LG45 protein by substituting the most critical basic residues with glutamine. All proteins were expressed in mammalian cells, purified, and characterized biochemically. We used in vitro binding assays, including surface plasmon resonance, to examine interactions between mutated LG45 and heparan sulfates, syndecan-1 and -4. We identify a major heparin binding domain on the outer edge of a β-strand of LG45 surrounded by a track of converging low affinity residues. This domain harbors distinctive syndecan-1 and -4 binding-specific sequences. This is the first study to demonstrate a binding specificity of two proteoglycans produced by a single cell type. In addition, we found that although syndecan-1 interacts exclusively through its glycosaminoglycan chains, syndecan-4 binding relies on both its core protein and its heparan sulfate chains. These results suggest that LG45 may trigger different signals toward keratinocytes depending on its interaction with syndecan-1 or -4.
authors.affiliation: Structure Fédérative de Recherche BioSciences Gerland-Lyon Sud, Institut de Biologie et Chimie des Protéines, FRE 3310, CNRS, Université Lyon 1, 7 Passage du Vercors, 69367 Lyon, France.
authors.forename: Sonia
authors.initials: S
authors.lastname: Carulli
authors.forename: Konrad
authors.initials: K
authors.lastname: Beck
authors.forename: Guila
authors.initials: G
authors.lastname: Dayan
authors.forename: Sophie
authors.initials: S
authors.lastname: Boulesteix
authors.forename: Hugues
authors.initials: H
authors.lastname: Lortat-Jacob
authors.forename: Patricia
authors.initials: P
authors.lastname: Rousselle
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D002846:Chromatography, Affinity; D006493:Heparin / Q000737:chemistry; D006497:Heparan Sulfate / Q000737:chemistry; D006801:Humans; D055767:Immobilized Proteins / Q000737:chemistry; D015603:Keratinocytes / Q000502:physiology; D007797:Laminin / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055550:Protein Stability; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D020349:Surface Plasmon Resonance; D053668:Syndecan-1 / Q000378:metabolism*; D053671:Syndecan-4 / Q000378:metabolism*
chemical_list: D006493:Heparin; D006497:Heparan Sulfate; D055767:Immobilized Proteins; D007797:Laminin; D011994:Recombinant Proteins; D053668:Syndecan-1; D053671:Syndecan-4; C508241:SDC1 protein, human; C508304:SDC4 protein, human; C095567:laminin alpha 3