title: Recombinant kringle 5 from plasminogen antagonises hepatocyte growth factor-mediated signalling.
abstract: The blood protein plasminogen is proteolytically cleaved to produce angiostatin and kringle 5 (K5), both of which are known angiogenesis inhibitors. A common structural element between K5, angiostatin and other endogenous angiogenesis inhibitors is the presence of the kringle protein-interacting domain. Another kringle domain-containing protein, hepatocyte growth factor (HGF), promotes angiogenesis by binding to and stimulating the tyrosine kinase receptor Met. HGF binding to Met is dependent on the kringle domains of HGF. Because both K5 and HGF contain kringle motifs and because these proteins have opposite effects on angiogenesis, we hypothesised that K5 can antagonise HGF-mediated signalling in a Met-dependent manner. We determined that K5 binding to H1299 cells is competed by HGF suggesting that these two proteins bind to the same protein. Purified K5 immunoprecipitates with Met and this interaction is abolished by increasing doses of HGF. Using proliferation, phosphorylation of Met and Akt as markers of HGF activity, we determined that K5 inhibits HGF-mediated signalling. Taken together, these data support a model by which K5 binds to Met and functions as a competitive antagonist of HGF signalling and presents a novel mechanism of action of K5.
authors.affiliation: Department of Cancer Research, Abbott Laboratories, Abbott Park, IL 60064, USA. peter.ansell@abbott.com
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Ansell
authors.forename: Haiying
authors.initials: H
authors.lastname: Zhang
authors.forename: Don J
authors.initials: DJ
authors.lastname: Davidson
authors.forename: John E
authors.initials: JE
authors.lastname: Harlan
authors.forename: John
authors.initials: J
authors.lastname: Xue
authors.forename: Sevan
authors.initials: S
authors.lastname: Brodjian
authors.forename: Rick
authors.initials: R
authors.lastname: Lesniewski
authors.forename: Evelyn
authors.initials: E
authors.lastname: McKeegan
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000818:Animals; D017228:Hepatocyte Growth Factor / Q000037:antagonists & inhibitors*; D006801:Humans; D010446:Peptide Fragments / Q000494:pharmacology*; D010843:Pichia; D010958:Plasminogen / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D020533:Angiogenesis Inhibitors; D010446:Peptide Fragments; D011994:Recombinant Proteins; C491499:plasminogen kringle 5; D017228:Hepatocyte Growth Factor; D010958:Plasminogen; D019859:Proto-Oncogene Proteins c-met; D051057:Proto-Oncogene Proteins c-akt