title: STAT1 activation by venous malformations mutant Tie2-R849W antagonizes VEGF-A-mediated angiogenic response partly via reduced bFGF production.
abstract: A missense mutation from arginine to tryptophan at residue 849 in the kinase domain of Tie2 (Tie2-R849W) is commonly identified in familial venous malformations. The mechanistic action of Tie2-R849W variant expression on angiogenic cascades including smooth muscle cell recruitment, however, remains elusive. To avoid confounding factors from endogenous Tie2 expression, Tie2-depleted endothelial cells (ECs) were used to study the effects of ectopic shRNA-resistant Tie2 variant expression, Tie2-WT* and Tie2-R849W*, on vascular cell proliferation, migration, tube formation, and smooth muscle cell (SMC) recruitment. Tie2-R849W* induced STAT1 phosphorylation at Tyr701. Tie2-R849W*-expressing cells had reduced ability to migrate and form tubes on Matrigel than their wildtype counterparts. STAT1 phosphorylation attenuated VEGF-A-induced STAT3 tyrosine phosphorylation in Tie2-R849W*-expressing HUVECs. The induced STAT1 activation also decreased VEGF-A-induced bFGF mRNA expression by competing with activated STAT3 for a direct binding to the consensus STAT-binding site at positions -997 to -989 bp from transcription start site in the bFGF promoter. Depleting STAT1 expression rescued the inability of Tie2-R849W expression to mediate angiogenesis. Moreover, bFGF neutralization or constitutive STAT1 activation, reminiscence of Tie2-R849W* expression, suppressed the smooth muscle cell recruiting ability of endothelial conditioned medium. This work reveals an anti-angiogenic role of STAT1 activation that acts in Tie2-R849W-expressing ECs to impair VEGF-A-mediated STAT3 signaling, bFGF production, and smooth muscle cell recruitment. A balancing activity of STAT1 and STAT3 may be important for Tie2-mediated vascular homeostasis.
authors.affiliation: Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC.
authors.forename: Yi-Hsien
authors.initials: YH
authors.lastname: Huang
authors.forename: Ming-Ping
authors.initials: MP
authors.lastname: Wu
authors.forename: Shin-Chen
authors.initials: SC
authors.lastname: Pan
authors.forename: Wu-Chou
authors.initials: WC
authors.lastname: Su
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Chen
authors.forename: Li-Wha
authors.initials: LW
authors.lastname: Wu
mesh_terms: D001483:Base Sequence; D002465:Cell Movement / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000378:metabolism / Q000473:pathology; D016222:Fibroblast Growth Factor 2 / Q000096:biosynthesis* / Q000235:genetics; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008969:Molecular Sequence Data; D020125:Mutation, Missense / Q000235:genetics*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018919:Neovascularization, Physiologic / Q000187:drug effects*; D009500:Neutralization Tests; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D042787:Receptor, TIE-2 / Q000235:genetics*; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology*; D054079:Vascular Malformations / Q000378:metabolism / Q000473:pathology*
chemical_list: D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; D019000:Phosphotyrosine; D042787:Receptor, TIE-2