title: Regulation of endothelial cell proliferation and vascular assembly through distinct mTORC2 signaling pathways.
abstract: Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that regulates a diverse array of cellular processes, including cell growth, survival, metabolism, and cytoskeleton dynamics. mTOR functions in two distinct complexes, mTORC1 and mTORC2, whose activities and substrate specificities are regulated by complex specific cofactors, including Raptor and Rictor, respectively. Little is known regarding the relative contribution of mTORC1 versus mTORC2 in vascular endothelial cells. Using mouse models of Raptor or Rictor gene targeting, we discovered that Rictor ablation inhibited vascular endothelial growth factor (VEGF)-induced endothelial cell proliferation and assembly in vitro and angiogenesis in vivo, whereas the loss of Raptor had only a modest effect on endothelial cells (ECs). Mechanistically, the loss of Rictor reduced the phosphorylation of AKT, protein kinase Cα (PKCα), and NDRG1 without affecting the mTORC1 pathway. In contrast, the loss of Raptor increased the phosphorylation of AKT despite inhibiting the phosphorylation of S6K1, a direct target of mTORC1. Reconstitution of Rictor-null cells with myristoylated AKT (Myr-AKT) rescued vascular assembly in Rictor-deficient endothelial cells, whereas PKCα rescued proliferation defects. Furthermore, tumor neovascularization in vivo was significantly decreased upon EC-specific Rictor deletion in mice. These data indicate that mTORC2 is a critical signaling node required for VEGF-mediated angiogenesis through the regulation of AKT and PKCα in vascular endothelial cells.
authors.affiliation: Division of Rheumatology and Immunology, Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Shan
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Katherine R
authors.initials: KR
authors.lastname: Amato
authors.affiliation: Division of Rheumatology and Immunology, Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Wenqiang
authors.initials: W
authors.lastname: Song
authors.affiliation: Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Victoria
authors.initials: V
authors.lastname: Youngblood
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, Tennessee, USA Hallym University, Chuncheon, Gangwon-do, South Korea.
authors.forename: Keunwook
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Boothby
authors.affiliation: Division of Rheumatology and Immunology, Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee, USA.
authors.forename: Dana M
authors.initials: DM
authors.lastname: Brantley-Sieders
authors.affiliation: Division of Rheumatology and Immunology, Department of Medicine, Vanderbilt University, Nashville, Tennessee, USA Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee, USA Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee, USA Veterans Affairs Medical Center, Tennessee Valley Healthcare System, Nashville, Tennessee, USA jin.chen@vanderbilt.edu.
authors.forename: Jin
authors.initials: J
authors.lastname: Chen
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology* / Q000378:metabolism; D017353:Gene Deletion; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D000076225:Mechanistic Target of Rapamycin Complex 2; D051379:Mice; D046912:Multiprotein Complexes / Q000378:metabolism*; D018919:Neovascularization, Physiologic; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D046912:Multiprotein Complexes; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; C540162:Rptor protein, mouse; D042461:Vascular Endothelial Growth Factor A; C525637:rictor protein, mouse; D000076225:Mechanistic Target of Rapamycin Complex 2; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D051571:Protein Kinase C-alpha