DGDA, a local sequence of the kringle 2 domain, is a functional motif of the tissue-type plasminogen activator’s antiangiogenic kringle domain

Abstract

Antiangiogenic activity can be elicited by the kringle domains 1 and 2 of tissue-type plasminogen activator (TK1–2), or the kringle 2 domain alone. In a previous report, we showed that the anti-migratory effect of TK1–2 is mediated in part by its interference with integrin α2β1. Since integrin α2β1 interacts with collagen type I through the DGEA (Asp-Gly-Glu-Ala) amino acid sequence, and a similar sequence, DGDA (Asp-Gly-Asp-Ala), exists in the kringle 2 domain, we investigated whether the DGDA sequence has a role in antiangiogenic activity of TK1–2. In an adhesion assay, the DGDA peptide inhibited adhesion of human umbilical vein endothelial cells (HUVECs) to immobilized TK1–2. Pretreatment of the DGDA peptide also blocked anti-migratory activity of TK1–2. When the DGDA peptide alone was tested for antiangiogenic activity, it effectively inhibited VEGF-induced migration of HUVECs and tube formation on Matrigel. In addition, the DGDA peptide decreased differentiation of endothelial progenitor cells on collagen type I matrix. These data suggest that the DGDA sequence presents a functional epitope of TK1–2 and that it can be used as a potential novel antiangiogenic peptide.