title: Calmodulin Mediates Ca2+-Dependent Inhibition of Tie2 Signaling and Acts as a Developmental Brake During Embryonic Angiogenesis.
abstract: Angiogenesis, the process of building complex vascular structures, begins with sprout formation on preexisting blood vessels, followed by extension of the vessels through proliferation and migration of endothelial cells. Based on the potential therapeutic benefits of preventing angiogenesis in pathological conditions, many studies have focused on the mechanisms of its initiation as well as control. However, how the extension of vessels is terminated remains obscure. Thus, we investigated the negative regulation mechanism.
  
  
  
  We report that increased intracellular calcium can induce dephosphorylation of the endothelial receptor tyrosine kinase Tie2. The calcium-mediated dephosphorylation was found to be dependent on Tie2-calmodulin interaction. The Tyr1113 residue in the C-terminal end loop of the Tie2 kinase domain was mapped and found to be required for this interaction. Moreover, mutation of this residue into Phe impaired both the Tie2-calmodulin interaction and calcium-mediated Tie2 dephosphorylation. Furthermore, expressing a mutant Tie2 incapable of binding to calmodulin or inhibiting calmodulin function in vivo causes unchecked growth of the vasculature in Xenopus. Specifically, knockdown of Tie2 in Xenopus embryo retarded the sprouting and extension of intersomitic veins. Although human Tie2 expression in the Tie2-deficient animals almost completely rescued the retardation, the Tie2(Y1113F) mutant caused overgrowth of intersomitic veins with strikingly complex and excessive branching patterns.
  
  
  
  We propose that the calcium/calmodulin-dependent negative regulation of Tie2 can be used as an inhibitory signal for vessel growth and branching to build proper vessel architecture during embryonic development.
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.).
authors.forename: Chansik
authors.initials: C
authors.lastname: Yang
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.).
authors.forename: Jiyeon
authors.initials: J
authors.lastname: Ohk
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.).
authors.forename: Ji Yeun
authors.initials: JY
authors.lastname: Lee
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.).
authors.forename: Eun Jin
authors.initials: EJ
authors.lastname: Kim
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.).
authors.forename: Jiyoon
authors.initials: J
authors.lastname: Kim
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.).
authors.forename: Sangyeul
authors.initials: S
authors.lastname: Han
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.).
authors.forename: Dongeun
authors.initials: D
authors.lastname: Park
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.). hosungjung@yonsei.ac.kr chungho@korea.ac.kr.
authors.forename: Hosung
authors.initials: H
authors.lastname: Jung
authors.affiliation: From the Department of Life Sciences, Korea University, Seoul, Republic of Korea (C.Y., J.Y.L., E.J.K., J.K., C.K.); School of Biological Sciences, Seoul National University, Seoul, Republic of Korea (C.Y., D.P.); Department of Anatomy, Brain Research Institute, and Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Republic of Korea (J.O., H.J.); and Center for Vascular Research, Institute for Basic Science, Daejeon, Korea (S.H.). hosungjung@yonsei.ac.kr chungho@korea.ac.kr.
authors.forename: Chungho
authors.initials: C
authors.lastname: Kim
mesh_terms: D000818:Animals; D016466:CHO Cells; D020013:Calcium Signaling; D002147:Calmodulin / Q000378:metabolism*; D003412:Cricetulus; D004625:Embryo, Nonmammalian / Q000098:blood supply* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D005838:Genotype; D057809:HEK293 Cells; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D018919:Neovascularization, Physiologic; D010641:Phenotype; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D042787:Receptor, TIE-2 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D014443:Tyrosine; D014981:Xenopus / Q000196:embryology* / Q000235:genetics / Q000378:metabolism
chemical_list: D002147:Calmodulin; D014443:Tyrosine; D042787:Receptor, TIE-2
keywords: Tie2; angiogenesis; calcium; calmodulin; embryogenesis