Mutation of human kringle 1–5 enhances the anti‐angiogenic action via increased interaction with integrin αvβ3

The anti‐angiogenic activities of kringle 1–5 (K 15 ) and kringle 5 (K 5 )fragments of plasminogen are higher than angiostatin (K 14 ) in inhibition of angiogenesis and angiogenesis‐dependent tumor growth. To further investigate the role of potential glycosylation residues (residue 289 and 346) of K 15 and Lys binding site (residue 532) at K 5 in anti‐angiogenesis, four different amino acid replaced mutants were made at these three residues, which are K 15 N289A (replaced Asn by Ala at residue 289), K 15 T346A, K 15 L532R, and K 15 N289A/T346A/L532R. Among these mutated proteins, K 15 N289A/T346A/L532R exhibited the highest effect in inhibition of endothelial cell proliferation and in inducing the apoptosis of endothelial cells. In vivo Matrigel assay showed that K 15 N289A/T346A/L532R was most potent in inhibition of bFGF‐induced angiogenesis. When systemically injected the K 15 N289A/T346A/L532R in mice, angiogenesis‐dependent tumor growth was inhibited. K 15 N289A/T346A/L532R was more effective on inhibition of bFGF‐induced Akt and eNOS phosphorylation than K 15 . Furthermore, integrin α v β 3 ‐mediated cell adhesion to K 15 N289A/T346A/L532R was enhanced comparing to wild type K 15 . In conclusion, alteration of glycosylation and Lys binding properties could increase the anti‐angiogenic action of K 15 via enhanced interaction with integrin α v β 3 in endothelial cells.