title: The binding capacity of α1β1-, α2β1- and α10β1-integrins depends on non-collagenous surface macromolecules rather than the collagens in cartilage fibrils.
abstract: Interactions of cells with supramolecular aggregates of the extracellular matrix (ECM) are mediated, in part, by cell surface receptors of the integrin family. These are important molecular components of cell surface-suprastructures regulating cellular activities in general. A subfamily of β1-integrins with von Willebrand-factor A-like domains (I-domains) in their α-chains can bind to collagen molecules and, therefore, are considered as important cellular mechano-receptors. Here we show that chondrocytes strongly bind to cartilage collagens in the form of individual triple helical molecules but very weakly to fibrils formed by the same molecules. We also find that chondrocyte integrins α1β1-, α2β1- and α10β1-integrins and their I-domains have the same characteristics. Nevertheless we find integrin binding to mechanically generated cartilage fibril fragments, which also comprise peripheral non-collagenous material. We conclude that cell adhesion results from binding of integrin-containing adhesion suprastructures to the non-collagenous fibril periphery but not to the collagenous fibril cores. The biological importance of the well-investigated recognition of collagen molecules by integrins is unknown. Possible scenarios may include fibrillogenesis, fibril degradation and/or phagocytosis, recruitment of cells to remodeling sites, or molecular signaling across cytoplasmic membranes. In these circumstances, collagen molecules may lack a fibrillar organization. However, other processes requiring robust biomechanical functions, such as fibril organization in tissues, cell division, adhesion, or migration, do not involve direct integrin-collagen interactions.
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Woltersdorf
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Bonk
authors.affiliation: National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK.
authors.forename: Birgit
authors.initials: B
authors.lastname: Leitinger
authors.affiliation: University of Turku, Department of Biochemistry, FI-20014 Turun Yliopisto, Finland.
authors.forename: Mikko
authors.initials: M
authors.lastname: Huhtala
authors.affiliation: University of Turku, Department of Biochemistry, FI-20014 Turun Yliopisto, Finland.
authors.forename: Jarmo
authors.initials: J
authors.lastname: Käpylä
authors.affiliation: University of Turku, Department of Biochemistry, FI-20014 Turun Yliopisto, Finland.
authors.forename: Jyrki
authors.initials: J
authors.lastname: Heino
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Gil Girol
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Niland
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany.
authors.forename: Johannes A
authors.initials: JA
authors.lastname: Eble
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany. Electronic address: peter.bruckner@uni-muenster.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Bruckner
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany.
authors.forename: Rita
authors.initials: R
authors.lastname: Dreier
authors.affiliation: Institute of Physiological Chemistry and Pathobiochemistry, University of Münster, D-48149 Münster, Germany; Institute of Experimental Musculoskeletal Medicine (IEMM), University of Münster, DE-48149 Münster, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Hansen
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology; D002417:Cattle; D002448:Cell Adhesion; D002478:Cells, Cultured; D002642:Chick Embryo; D019902:Chondrocytes / Q000502:physiology*; D000070818:Discoidin Domain Receptors / Q000502:physiology; D024022:Fibrillar Collagens / Q000737:chemistry* / Q000502:physiology; D006801:Humans; D055767:Immobilized Proteins / Q000737:chemistry; D039001:Integrin alpha Chains / Q000737:chemistry* / Q000502:physiology; D039222:Integrin alpha1beta1 / Q000737:chemistry* / Q000502:physiology; D038982:Integrin alpha2beta1 / Q000737:chemistry* / Q000502:physiology; D011485:Protein Binding
chemical_list: D024022:Fibrillar Collagens; D055767:Immobilized Proteins; D039001:Integrin alpha Chains; D039222:Integrin alpha1beta1; D038982:Integrin alpha2beta1; C406210:integrin alpha 10; D000070818:Discoidin Domain Receptors
keywords: Adaptor proteins; Cell-matrix-interactions; Mechanoreception; Suprastructure