| Distinct roles of the mTOR components Rictor and Raptor in MO7e megakaryocytic cells. | |
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MedLine Citation:
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PMID: 19341427 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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OBJECTIVE: During megakaryopoiesis, hematopoietic progenitor cells in the bone marrow proliferate and ultimately differentiate in mature megakaryocytes (MK). We and others have recently described a role for the mammalian target of Rapamycin (mTOR) in proliferation and differentiation of MK cells. Two non-redundant complexes of mTOR have been described; mTORC1 containing rapamycin-associated TOR protein (Raptor) and mTORC2 containing Rapamycin-insensitive companion of mTOR (Rictor). The individual roles of these complexes in MK development have so far not been elucidated, and were investigated in this study. METHODS: We have used an siRNA approach to selectively knock down either Rictor or Raptor expression in MO7e megakaryoblastic cells. Using flow cytometry, nuclear ploidity, and cell cycling as assessed by BrdU incorporation were investigated. Electron microscopy and cotransductions with GFP-LC3 were used to quantify autophagy. Activation of intracellular signal transduction pathways was studied by Western blot analysis. RESULTS: We observed a reduced cell cycling upon Rictor siRNA transduction, resulting in decreased numbers of polypoid cells. Knocking down Raptor expression resulted in a reduced expansion and a reduced cell size. In addition, increased autophagy was observed in Raptor siRNA-transduced cells, in correspondence with an attenuation of activation of the p70S6K/S6, and 4E-BP pathways. CONCLUSIONS: The current study shows that the mTORC1 and mTORC2 complexes have distinct, non-redundant functions in MO7e MK cell proliferation, and development. The mTOR/Rictor complex affects megakaryopoiesis by regulating nuclear division and subsequent cell cycle progression, whereas Raptor signaling protects MK cells from autophagic cell death, enabling normal megakaryopoiesis to take place. |
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Authors:
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Gwenny M Fuhler; Monika R Tyl; Sandra G M Olthof; A Lyndsay Drayer; Nel Blom; Edo Vellenga |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2009-04-01 |
Journal Detail:
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Title: European journal of haematology Volume: 83 ISSN: 1600-0609 ISO Abbreviation: Eur. J. Haematol. Publication Date: 2009 Sep |
Date Detail:
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Created Date: 2009-08-19 Completed Date: 2009-09-02 Revised Date: 2010-12-13 |
Medline Journal Info:
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Nlm Unique ID: 8703985 Medline TA: Eur J Haematol Country: England |
Other Details:
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Languages: eng Pagination: 235-45 Citation Subset: IM |
Affiliation:
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Division of Hematology, Department of Medicine, University Medical Center Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands. g.m.fuhler@med.umcg.nl |
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| MeSH Terms | |
Descriptor/Qualifier:
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Adaptor Proteins, Signal Transducing Bone Marrow Cells / cytology Carrier Proteins / metabolism* Cell Proliferation Flow Cytometry / methods Gene Expression Regulation* Genetic Vectors Green Fluorescent Proteins / metabolism Humans Megakaryocytes / metabolism* Phosphotransferases (Alcohol Group Acceptor) / metabolism* Proteins / metabolism* RNA, Small Interfering / metabolism Signal Transduction TOR Serine-Threonine Kinases Transcription Factors / metabolism |
| Chemical | |
Reg. No./Substance:
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0/Adaptor Proteins, Signal Transducing; 0/CRTC2 protein, human; 0/Carrier Proteins; 0/Proteins; 0/RICTOR protein, human; 0/RNA, Small Interfering; 0/RPTOR protein, human; 0/Transcription Factors; 0/mTORC1 complex, human; 147336-22-9/Green Fluorescent Proteins; EC 2.7.1.-/Phosphotransferases (Alcohol Group Acceptor); EC 2.7.1.1/MTOR protein, human; EC 2.7.1.1/TOR Serine-Threonine Kinases |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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