title: Decorin is a novel VEGFR-2-binding antagonist for the human extravillous trophoblast.
abstract: Extravillous trophoblasts (EVT) of the human placenta invade the uterine decidua and its arteries to ensure successful placentation. We previously identified two decidua-derived molecules, TGF-β and a TGF-β-binding proteoglycan decorin (DCN), as negative regulators of EVT proliferation, migration, and invasiveness and reported that DCN acts via multiple tyrosine kinase receptors [epidermal growth factor-receptor (EGF-R), IGF receptor-1 (IGFR1), and vascular endothelial growth factor 2 receptor (VEGFR-2)]. Because binding of DCN to VEGFR-2 has never been reported earlier, present study explored this binding, the approximate location of VEGFR-2-binding site in DCN, and its functional role in our human first trimester EVT cell line HTR-8/SVneo. Based on far-Western blotting and coimmunoprecipitation studies, we report that DCN binds both native (EVT expressed) and recombinant VEGFR-2 and that this binding is abrogated with a VEGFR-2 blocking antibody, indicating an overlap between the ligand-binding and the DCN-binding domains of VEGFR-2. We determined that (125)I-labeled VEGF-E (a VEGFR-2 specific ligand) binds EVT with a dissociation constant (K(d)) of 566 pM, and DCN displaced this binding with an inhibition constant (K(i)) of 3.93-5.78 nM, indicating a 7- to 10-fold lower affinity of DCN for VEGFR-2. DCN peptide fragments derived from the leucine rich repeat 5 domain that blocked DCN-VEGFR-2 interactions or VEGF-E binding in EVT cells also blocked VEGF-A- and VEGF-E-induced EVT cell proliferation and migration, indicative of functional VEGFR-2-binding sites of DCN. Finally, DCN inhibited VEGF-E-induced EVT migration by interfering with ERK1/2 activation. Our findings reveal a novel role of DCN as an antagonistic ligand for VEGFR-2, having implications for pathophysiology of preeclampsia, a trophoblast hypoinvasive disorder in pregnancy, and explain its antiangiogenic function.
authors.affiliation: Department of Anatomy & Cell Biology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.
authors.forename: Gausal A
authors.initials: GA
authors.lastname: Khan
authors.forename: Gannareddy V
authors.initials: GV
authors.lastname: Girish
authors.forename: Neena
authors.initials: N
authors.lastname: Lala
authors.forename: Gianni M
authors.initials: GM
authors.lastname: Di Guglielmo
authors.forename: Peeyush K
authors.initials: PK
authors.lastname: Lala
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D026481:Blotting, Far-Western; D002417:Cattle; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D058575:Decorin / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D059951:HLA-G Antigens / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008024:Ligands; D008954:Models, Biological; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D014327:Trophoblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism
chemical_list: D058575:Decorin; D059951:HLA-G Antigens; D008024:Ligands; D010455:Peptides; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; D048049:Extracellular Signal-Regulated MAP Kinases