title: Tie2-R849W mutant in venous malformations chronically activates a functional STAT1 to modulate gene expression.
abstract: Tie2 is an endothelial receptor tyrosine kinase. An amino-acid substitution of tryptophan for arginine at residue 849 (Tie2-R849W) leads to a ligand-independent activation of its kinase activity. This mutation has been associated with familial venous malformations (VMs), manifested by variable thickness or lack of smooth-muscle cells in the veins of patient lesions. The underlying mechanism for Tie2-R849W action in endothelial cells remains elusive. In this study, we used adenoviral infection to differentiate the effects of ectopic Tie2 (wild type, kinase-dead K855A, or constitutively active R849W) expression on endothelial cellular behaviors and Tie2-mediated downstream targets. Ectopic Tie2 reduced endothelial cell proliferation and serum withdrawal-induced apoptosis, while stimulating migration. When comparing R849W with K855A and its wild-type counterpart, a functional tyrosine kinase activity was required only for migration, and constitutively active Tie2-R849W conferred highest resistance to serum-induced apoptosis, but lowest ability to maintain tube-like structures formed on Matrigel. We further demonstrated that Tie2-R849W chronically induced STAT1 tyrosine phosphorylation and the promoter activity of STAT1-responsive IFN-regulatory factor 1 (IRF1). Although STAT1 phosphorylation required JNK and p38MAPK activation, only JNK activation was essential for IRF1 promoter activation by Tie2-R849W. Additional studies are needed to study the role of STAT1 activation in VMs.
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan, ROC.
authors.forename: Hsiao-Tang
authors.initials: HT
authors.lastname: Hu
authors.forename: Yi-Hsien
authors.initials: YH
authors.lastname: Huang
authors.forename: Yi-Ann
authors.initials: YA
authors.lastname: Chang
authors.forename: Chien-Kuo
authors.initials: CK
authors.lastname: Lee
authors.forename: Meei-Jyh
authors.initials: MJ
authors.lastname: Jiang
authors.forename: Li-Wha
authors.initials: LW
authors.lastname: Wu
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology; D017209:Apoptosis / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D005260:Female; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D042787:Receptor, TIE-2 / Q000235:genetics* / Q000378:metabolism*; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014471:Umbilical Veins / Q000166:cytology / Q000378:metabolism; D054079:Vascular Malformations / Q000235:genetics* / Q000378:metabolism*; D014680:Veins / Q000002:abnormalities* / Q000378:metabolism
chemical_list: C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D042787:Receptor, TIE-2; D048670:MAP Kinase Kinase 4