title: Angiostatin K1-3 induces E-selectin via AP1 and Ets1: a mediator for anti-angiogenic action of K1-3.
abstract: BACKGROUND
  Angiostatin, a circulating angiogenic inhibitor, is an internal fragment of plasminogen and consists of several isoforms, K1-3 included. We previously showed that K1-3 was the most potent angiostatin to induce E-selectin mRNA expression. The purpose of this study was to identify the mechanism responsible for K1-3-induced E-selectin expression and investigate the role of E-selectin in the anti-angiogenic action of K1-3.
  
  
  RESULTS
  Quantitative real time RT-PCR and Western blotting analyses confirmed a time-dependent increase of E-selectin mRNA and protein induced by K1-3. Subcellular fractionation and immunofluorescence microscopy showed the co-localization of K1-3-induced E-selectin with caveolin 1 (Cav1) in lipid rafts in which E-selectin may behave as a signaling receptor. Promoter-driven reporter assays and site-directed mutagenesis showed that K1-3 induced E-selectin expression via promoter activation and AP1 and Ets-1 binding sites in the proximal E-selectin promoter were required for E-selectin induction. The in vivo binding of both protein complexes to the proximal promoter was confirmed by chromatin immunoprecipitation (ChIP). Although K1-3 induced the activation of ERK1/2 and JNK, only repression of JNK activation attenuated the induction of E-selectin by K1-3. A modulatory role of E-selectin in the anti-angiogenic action of K1-3 was manifested by both overexpression and knockdown of E-selectin followed by cell proliferation assay.
  
  
  CONCLUSIONS
  We show that K1-3 induced E-selectin expression via AP1 and Ets-1 binding to the proximal E-selectin promoter (-356/+1), which was positively mediated by JNK activation. Our findings also demonstrate E-selectin as a novel target for the anti-angiogenic therapy.
authors.affiliation: Institute of Basic Medical Sciences, College of Mdicine, National Cheng Kung University, Tainan, Taiwa, ROC.
authors.forename: Y-H
authors.initials: YH
authors.lastname: Chen
authors.forename: Y-H
authors.initials: YH
authors.lastname: Huang
authors.forename: H-L
authors.initials: HL
authors.lastname: Wu
authors.forename: M-P
authors.initials: MP
authors.lastname: Wu
authors.forename: W-T
authors.initials: WT
authors.lastname: Chang
authors.forename: Y-Z
authors.initials: YZ
authors.lastname: Kuo
authors.forename: K-C
authors.initials: KC
authors.lastname: Lu
authors.forename: L-W
authors.initials: LW
authors.lastname: Wu