Distinct roles of the mTOR components Rictor and Raptor in MO7e megakaryocytic cells

Autor: Sandra Olthof, Monika R. Tyl, Edo Vellenga, Gwenny M. Fuhler, A. Lyndsay Drayer, Nel R. Blom
Přispěvatelé: Guided Treatment in Optimal Selected Cancer Patients (GUTS), Stem Cell Aging Leukemia and Lymphoma (SALL)
Jazyk: angličtina
Rok vydání: 2009
Předmět:
Programmed cell death
KINASE-B
Genetic Vectors
Green Fluorescent Proteins
INHIBITION
Bone Marrow Cells
mTORC1
Biology
Mechanistic Target of Rapamycin Complex 1
mTORC2
Rictor
ACTIVATION
Humans
Progenitor cell
RNA
Small Interfering

PHOSPHORYLATION
PI3K/AKT/mTOR pathway
Adaptor Proteins
Signal Transducing

Cell Proliferation
PROGENITORS
Cell growth
TOR Serine-Threonine Kinases
RPTOR
THROMBOPOIETIN-INDUCED PROLIFERATION
Proteins
Hematology
General Medicine
Regulatory-Associated Protein of mTOR
Flow Cytometry
CD34(+) CELLS
Cell biology
Raptor
Intracellular signal transduction
Phosphotransferases (Alcohol Group Acceptor)
Rapamycin-Insensitive Companion of mTOR Protein
Gene Expression Regulation
MAMMALIAN TARGET
RIBOSOMAL-PROTEIN S6
Multiprotein Complexes
Carrier Proteins
RAPAMYCIN
Megakaryocytes
megakaryopoiesis
signal transduction
Transcription Factors
Zdroj: European Journal of Haematology, 83(3), 235-245. Wiley
ISSN: 0902-4441
DOI: 10.1111/j.1600-0609.2009.01263.x
Popis: 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.
Databáze: OpenAIRE