title: Critical role for PI 3-kinase in the control of erythropoietin-induced erythroid progenitor proliferation.
abstract: The production of red blood cells is tightly regulated by erythropoietin (Epo). The phosphoinositide 3-kinase (PI 3-kinase) pathway was previously shown to be activated in response to Epo. We studied the role of this pathway in the control of Epo-induced survival and proliferation of primary human erythroid progenitors. We show that phosphoinositide 3 (PI 3)-kinase associates with 4 tyrosine-phosphorylated proteins in primary human erythroid progenitors, namely insulin receptor substrate-2 (IRS2), Src homology 2 domain-containing inositol 5'-phosphatase (SHIP), Grb2-associated binder-1 (Gab1), and the Epo receptor (EpoR). Using different in vitro systems, we demonstrate that 3 alternative pathways independently lead to Epo-induced activation of PI 3-kinase and phosphorylation of its downstream effectors, Akt, FKHRL1, and P70S6 kinase: through direct association of PI 3-kinase with the last tyrosine residue (Tyr479) of the Epo receptor (EpoR), through recruitment and phosphorylation of Gab proteins via either Tyr343 or Tyr401 of the EpoR, or through phosphorylation of IRS2 adaptor protein. The mitogen-activated protein (MAP) kinase pathway was also activated by Epo in erythroid progenitors, but we found that this process is independent of PI 3-kinase activation. In erythroid progenitors, the functional role of PI 3-kinase was both to prevent apoptosis and to stimulate cell proliferation in response to Epo stimulation. Finally, our results show that PI 3-kinase-mediated proliferation of erythroid progenitors in response to Epo occurs mainly through modulation of the E3 ligase SCF(SKP2), which, in turn, down-regulates p27(Kip1) cyclin-dependent kinase (CDK) inhibitor via proteasome degradation.
authors.affiliation: Département d'Hématologie, Institut Cochin, Institut National de la Santé et de la Recherche Médicale U567, Centre National de la Recherche Scientifique, UMR 8104, Université René Descartes, Paris, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Bouscary
authors.forename: Frédéric
authors.initials: F
authors.lastname: Pene
authors.forename: Yann-Erick
authors.initials: YE
authors.lastname: Claessens
authors.forename: Odile
authors.initials: O
authors.lastname: Muller
authors.forename: Stany
authors.initials: S
authors.lastname: Chrétien
authors.forename: Michaëla
authors.initials: M
authors.lastname: Fontenay-Roupie
authors.forename: Sylvie
authors.initials: S
authors.lastname: Gisselbrecht
authors.forename: Patrick
authors.initials: P
authors.lastname: Mayeux
authors.forename: Catherine
authors.initials: C
authors.lastname: Lacombe
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division; D002470:Cell Survival; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D002867:Chromones / Q000494:pharmacology; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004921:Erythropoietin / Q000494:pharmacology / Q000502:physiology*; D005312:Fetal Blood / Q000166:cytology; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D006801:Humans; D007231:Infant, Newborn; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008025:Ligases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D017467:Receptors, Erythropoietin / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D002867:Chromones; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003546:Cysteine Endopeptidases; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D004921:Erythropoietin; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008025:Ligases; D009025:Morpholines; D009097:Multienzyme Complexes; D019869:Phosphatidylinositol 3-Kinases; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D010744:Phosphoric Monoester Hydrolases; D046988:Proteasome Endopeptidase Complex; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D017467:Receptors, Erythropoietin; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D020123:Sirolimus; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D044767:Ubiquitin-Protein Ligases; C493961:Cdkn1b protein, mouse; C085126:FOXO1 protein, human; C499517:FOXO3 protein, human; C474033:FoxO3 protein, mouse; C098587:GAB1 protein, human; C490897:Gab1 protein, mouse; C526297:IRS2 protein, human; C526298:Irs2 protein, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C494918:AKT1 protein, human; C098706:INPPL1 protein, human