title: Exploring the collagen-binding site of the DDR1 tyrosine kinase receptor.
abstract: Discoidin domain receptors 1 and 2 (DDR1 and DDR2) are tyrosine kinase receptors activated by triple-helical collagens. Aberrant expression and signaling of these receptors have been implicated in several human diseases linked to accelerated matrix degradation and remodeling including tumor invasion, atherosclerosis and liver fibrosis. The objective of this study is to characterize the collagen-binding sites in the discoidin domains of DDR1 and DDR2 at a molecular level. We expressed glutathione S-transferase fusion proteins containing the discoidin and extracellular domains of DDR1 and DDR2 in insect cells and subjected them to a solid-phase collagen-binding assay. We found high affinity binding of the DDR extracellular domains to immobilized type I collagen and confirmed the discoidin-collagen interaction with an enzyme-linked immunosorbent assay-based read-out. Furthermore, we created a three-dimensional model of the DDR1 discoidin domain based on the related domains of blood coagulation factors V and VIII. This model predicts the presence of four neighboring, surface-exposed loops that are topologically equivalent to a major phospholipid-binding site in factors V and VIII. To test the involvement of these loops in collagen binding, we mutated individual amino acid residues to alanine or deleted short sequence stretches within these loops. We found that several residues within loop 1 (Ser-52-Thr-57) and loop 3 (Arg-105-Lys-112) as well as Ser-175 in loop 4 are critically involved in collagen binding. Our structure-function analysis of the DDR discoidin domains provides new insights into this non-integrin-mediated collagen-signaling mechanism and may ultimately lead to the design of small molecule inhibitors that interfere with aberrant DDR function.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Rahim
authors.initials: R
authors.lastname: Abdulhussein
authors.forename: Catherine
authors.initials: C
authors.lastname: McFadden
authors.forename: Pablo
authors.initials: P
authors.lastname: Fuentes-Prior
authors.forename: Wolfgang F
authors.initials: WF
authors.lastname: Vogel
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D003094:Collagen / Q000378:metabolism*; D000070819:Discoidin Domain Receptor 1; D000070818:Discoidin Domain Receptors; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011975:Receptors, Mitogen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D011975:Receptors, Mitogen; D011993:Recombinant Fusion Proteins; D003094:Collagen; C092030:DDR1 protein, human; D000070819:Discoidin Domain Receptor 1; D000070818:Discoidin Domain Receptors; D020794:Receptor Protein-Tyrosine Kinases