ABSTRACT
Angiogenin is one of the most potent angiogenesis-inducing proteins. Angiostatin is one of the most potent angiogenesis inhibitors, and it contains the first four kringle domains of plasminogen (K1-4). Recombinant human plasminogen kringle 1-3 (rK1-3) was expressed in Escherichia coli and purified to homogeneity. The binding of t-4-aminomethylcyclohexanecarboxylic acid with the purified kringle 1-3 was determined by changes in intrinsic fluorescence. rK1-3 exhibits comparable ligand-binding properties as native human plasminogen kringle 1-3. The purified rK1-3 inhibits neovascularization in the chick embryo chorioallantoic membrane (CAM) assay. Interaction of angiogenin with rK1-3 was examined by immunological binding assay and surface plasmon resonance kinetic analysis, and the equilibrium dissociation constants for the complex, Kd, are 0.89 and 0.18 microM, respectively. rK1-3 inhibits angiogenin-induced angiogenesis in the chick embryo CAM in a concentration-dependent manner. These results indicate that rK1-3 directly binds to angiogenin and thus rK1-3 inhibits the angiogenic activity of angiogenin.
Subject(s)
Angiogenesis Inhibitors/metabolism , Chorioallantoic Membrane/blood supply , Neovascularization, Physiologic , Peptide Fragments/metabolism , Plasminogen/metabolism , Ribonuclease, Pancreatic/antagonists & inhibitors , Angiogenesis Inhibitors/isolation & purification , Animals , Chick Embryo , Enzyme-Linked Immunosorbent Assay , Ligands , Peptide Fragments/isolation & purification , Plasminogen/isolation & purification , Ribonuclease, Pancreatic/metabolism , Surface Plasmon ResonanceABSTRACT
Angiogenesis, the formation of new capillaries from preexisting blood vessels, is involved in many pathological conditions, for example, tumorigenesis, diabetic retinopathy, and rheumatoid arthritis. Angiostatin, which contains the kringle 1-4 domains of plasminogen, is known to be a potent inhibitor of angiogenesis and a strong suppressor of various solid tumors. In this study, we expressed recombinant protein containing the kringle 1-3 domains of human plasminogen in Escherichia coli and investigated its biological activities. The protein was successfully refolded from inclusion bodies and purified at a 30% overall yield, as a single peak by HPLC. The purified recombinant protein had biochemical properties that were similar to those of the native form, which included molecular size, lysine-binding capacity, and immunoreactivity with a specific antibody. The recombinant protein was also found to strongly inhibit the proliferation of bovine capillary endothelial cells in vitro, and the formation of new capillaries on chick embryos. In addition, it suppressed the growth of primary Lewis lung carcinoma and B16 melanoma in an in vivo mouse model. Our findings suggest that the recombinant kringle 1-3 domains in a prokaryote expression system have anti-angiogenic activities, which may be useful in clinical and basic research in the field of angiogenesis.
