title: Phosphatidylinositol 3-kinase class II α-isoform PI3K-C2α is required for transforming growth factor β-induced Smad signaling in endothelial cells.
abstract: We have recently demonstrated that the PI3K class II-α isoform (PI3K-C2α), which generates phosphatidylinositol 3-phosphate and phosphatidylinositol 3,4-bisphosphates, plays crucial roles in angiogenesis, by analyzing PI3K-C2α knock-out mice. The PI3K-C2α actions are mediated at least in part through its participation in the internalization of VEGF receptor-2 and sphingosine-1-phosphate receptor S1P1 and thereby their signaling on endosomes. TGFβ, which is also an essential angiogenic factor, signals via the serine/threonine kinase receptor complex to induce phosphorylation of Smad2 and Smad3 (Smad2/3). SARA (Smad anchor for receptor activation) protein, which is localized in early endosomes through its FYVE domain, is required for Smad2/3 signaling. In the present study, we showed that PI3K-C2α knockdown nearly completely abolished TGFβ1-induced phosphorylation and nuclear translocation of Smad2/3 in vascular endothelial cells (ECs). PI3K-C2α was necessary for TGFβ-induced increase in phosphatidylinositol 3,4-bisphosphates in the plasma membrane and TGFβ receptor internalization into the SARA-containing early endosomes, but not for phosphatidylinositol 3-phosphate enrichment or localization of SARA in the early endosomes. PI3K-C2α was also required for TGFβ receptor-mediated formation of SARA-Smad2/3 complex. Inhibition of dynamin, which is required for the clathrin-dependent receptor endocytosis, suppressed both TGFβ receptor internalization and Smad2/3 phosphorylation. TGFβ1 stimulated Smad-dependent VEGF-A expression, VEGF receptor-mediated EC migration, and capillary-like tube formation, which were all abolished by either PI3K-C2α knockdown or a dynamin inhibitor. Finally, TGFβ1-induced microvessel formation in Matrigel plugs was greatly attenuated in EC-specific PI3K-C2α-deleted mice. These observations indicate that PI3K-C2α plays the pivotal role in TGFβ receptor endocytosis and thereby Smad2/3 signaling, participating in angiogenic actions of TGFβ.
authors.affiliation: From the Department of Physiology, Kanazawa University School of Medicine, Kanazawa, Ishikawa 920-8640, Japan and.
authors.forename: Sho
authors.initials: S
authors.lastname: Aki
authors.affiliation: From the Department of Physiology, Kanazawa University School of Medicine, Kanazawa, Ishikawa 920-8640, Japan and.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Yoshioka
authors.affiliation: From the Department of Physiology, Kanazawa University School of Medicine, Kanazawa, Ishikawa 920-8640, Japan and.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Okamoto
authors.affiliation: From the Department of Physiology, Kanazawa University School of Medicine, Kanazawa, Ishikawa 920-8640, Japan and the Department of Health and Medical Sciences, Ishikawa Prefectural Nursing University, Kahoku, Ishikawa 929-1210, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Takuwa
authors.affiliation: From the Department of Physiology, Kanazawa University School of Medicine, Kanazawa, Ishikawa 920-8640, Japan and ytakuwa@med.kanazawa-u.ac.jp.
authors.forename: Yoh
authors.initials: Y
authors.lastname: Takuwa
mesh_terms: D000818:Animals; D004705:Endocytosis / Q000235:genetics*; D042783:Endothelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics*; D012697:Serine Endopeptidases / Q000096:biosynthesis / Q000235:genetics*; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000235:genetics* / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; D019869:Phosphatidylinositol 3-Kinases; C546621:PIK3C2A protein, human; C116420:ZFYVE16 protein, human; D012697:Serine Endopeptidases
keywords: Endosome; Endothelial Cell; PI3K-C2alpha; Phosphatidylinositol Kinase (PI Kinase); Receptor Endocytosis; SARA; SMAD Transcription Factor; TGF-B Receptor; Transforming Growth Factor Beta (TGF-B); Vascular Endothelial Growth Factor (VEGF)