title: Vascular injury triggers Krüppel-like factor 6 mobilization and cooperation with specificity protein 1 to promote endothelial activation through upregulation of the activin receptor-like kinase 1 gene.
abstract: BACKGROUND
  Activin receptor-like kinase-1 (ALK1) is an endothelial transforming growth factor β receptor involved in angiogenesis. ALK1 expression is high in the embryo vasculature, becoming less detectable in the quiescent endothelium of adult stages. However, ALK1 expression becomes rapidly increased after angiogenic stimuli such as vascular injury.
  
  
  OBJECTIVE
  To characterize the molecular mechanisms underlying the regulation of ALK1 on vascular injury.
  
  
  RESULTS
  Alk1 becomes strongly upregulated in endothelial (EC) and vascular smooth muscle cells of mouse femoral arteries after wire-induced endothelial denudation. In vitro denudation of monolayers of human umbilical vein ECs also leads to an increase in ALK1. Interestingly, a key factor in tissue remodeling, Krüppel-like factor 6 (KLF6) translocates to the cell nucleus during wound healing, concomitantly with an increase in the ALK1 gene transcriptional rate. KLF6 knock down in human umbilical vein ECs promotes ALK1 mRNA downregulation. Moreover, Klf6(+/-) mice have lower levels of Alk1 in their vasculature compared with their wild-type siblings. Chromatin immunoprecipitation assays show that KLF6 interacts with ALK1 promoter in ECs, and this interaction is enhanced during wound healing. We demonstrate that KLF6 is transactivating ALK1 gene, and this transactivation occurs by a synergistic cooperative mechanism with specificity protein 1. Finally, Alk1 levels in vascular smooth muscle cells are not directly upregulated in response to damage, but in response to soluble factors, such as interleukin 6, released from ECs after injury.
  
  
  CONCLUSIONS
  ALK1 is upregulated in ECs during vascular injury by a synergistic cooperative mechanism between KLF6 and specificity protein 1, and in vascular smooth muscle cells by an EC-vascular smooth muscle cell paracrine communication during vascular remodeling.
authors.affiliation: Centro de Investigaciones Biológica, Ramiro de Maeztu 9, 28040, Madrid, Spain.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Garrido-Martín
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Blanco
authors.forename: Mercé
authors.initials: M
authors.lastname: Roquè
authors.forename: Laura
authors.initials: L
authors.lastname: Novensà
authors.forename: Mirko
authors.initials: M
authors.lastname: Tarocchi
authors.forename: Ursula E
authors.initials: UE
authors.lastname: Lang
authors.forename: Toru
authors.initials: T
authors.lastname: Suzuki
authors.forename: Scott L
authors.initials: SL
authors.lastname: Friedman
authors.forename: Luisa M
authors.initials: LM
authors.lastname: Botella
authors.forename: Carmelo
authors.initials: C
authors.lastname: Bernabéu
mesh_terms: D030201:Activin Receptors, Type I / Q000235:genetics / Q000378:metabolism*; D030301:Activin Receptors, Type II / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000378:metabolism* / Q000473:pathology; D005263:Femoral Artery / Q000293:injuries / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D019899:Paracrine Communication; D011401:Promoter Regions, Genetic; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D057772:Vascular System Injuries / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014945:Wound Healing
chemical_list: D015850:Interleukin-6; C105465:KLF6 protein, human; C491358:Klf6 protein, mouse; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; C425364:ACVRL1 protein, human; D030201:Activin Receptors, Type I; D030301:Activin Receptors, Type II; C498931:Acvrl1 protein, mouse