PMID- 19341427
OWN - NLM
STAT- MEDLINE
DCOM- 20090902
LR  - 20211203
IS  - 1600-0609 (Electronic)
IS  - 0902-4441 (Linking)
VI  - 83
IP  - 3
DP  - 2009 Sep
TI  - Distinct roles of the mTOR components Rictor and Raptor in MO7e megakaryocytic 
      cells.
PG  - 235-45
LID - 10.1111/j.1600-0609.2009.01263.x [doi]
AB  - 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.
FAU - Fuhler, Gwenny M
AU  - Fuhler GM
AD  - Division of Hematology, Department of Medicine, University Medical Center 
      Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands. 
      g.m.fuhler@med.umcg.nl
FAU - Tyl, Monika R
AU  - Tyl MR
FAU - Olthof, Sandra G M
AU  - Olthof SG
FAU - Lyndsay Drayer, A
AU  - Lyndsay Drayer A
FAU - Blom, Nel
AU  - Blom N
FAU - Vellenga, Edo
AU  - Vellenga E
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20090401
PL  - England
TA  - Eur J Haematol
JT  - European journal of haematology
JID - 8703985
RN  - 0 (Adaptor Proteins, Signal Transducing)
RN  - 0 (CRTC2 protein, human)
RN  - 0 (Carrier Proteins)
RN  - 0 (Multiprotein Complexes)
RN  - 0 (Proteins)
RN  - 0 (RICTOR protein, human)
RN  - 0 (RNA, Small Interfering)
RN  - 0 (RPTOR protein, human)
RN  - 0 (Rapamycin-Insensitive Companion of mTOR Protein)
RN  - 0 (Regulatory-Associated Protein of mTOR)
RN  - 0 (Transcription Factors)
RN  - 147336-22-9 (Green Fluorescent Proteins)
RN  - EC 2.7.1.- (Phosphotransferases (Alcohol Group Acceptor))
RN  - EC 2.7.1.1 (MTOR protein, human)
RN  - EC 2.7.11.1 (Mechanistic Target of Rapamycin Complex 1)
RN  - EC 2.7.11.1 (TOR Serine-Threonine Kinases)
SB  - IM
MH  - Adaptor Proteins, Signal Transducing
MH  - Bone Marrow Cells/cytology
MH  - Carrier Proteins/*metabolism
MH  - Cell Proliferation
MH  - Flow Cytometry/methods
MH  - *Gene Expression Regulation
MH  - Genetic Vectors
MH  - Green Fluorescent Proteins/metabolism
MH  - Humans
MH  - Mechanistic Target of Rapamycin Complex 1
MH  - Megakaryocytes/*metabolism
MH  - Multiprotein Complexes
MH  - Phosphotransferases (Alcohol Group Acceptor)/*metabolism
MH  - Proteins/*metabolism
MH  - RNA, Small Interfering/metabolism
MH  - Rapamycin-Insensitive Companion of mTOR Protein
MH  - Regulatory-Associated Protein of mTOR
MH  - Signal Transduction
MH  - TOR Serine-Threonine Kinases
MH  - Transcription Factors/metabolism
EDAT- 2009/04/04 09:00
MHDA- 2009/09/03 06:00
CRDT- 2009/04/04 09:00
PHST- 2009/04/04 09:00 [entrez]
PHST- 2009/04/04 09:00 [pubmed]
PHST- 2009/09/03 06:00 [medline]
AID - EJH1263 [pii]
AID - 10.1111/j.1600-0609.2009.01263.x [doi]
PST - ppublish
SO  - Eur J Haematol. 2009 Sep;83(3):235-45. doi: 10.1111/j.1600-0609.2009.01263.x. 
      Epub 2009 Apr 1.