Critical role for PI 3-kinase in the control of erythropoietin-induced erythroid progenitor proliferation.
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.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Animals, Apoptosis, Cell Cycle Proteins, Cell Division, Cell Survival, Cells, Cultured, Chromones, Cyclin-Dependent Kinase Inhibitor p27, Cysteine Endopeptidases, DNA-Binding Proteins, Enzyme Activation, Enzyme Inhibitors, Erythroid Precursor Cells, Erythropoietin, Fetal Blood, Forkhead Transcription Factors, Humans, Infant, Newborn, Insulin Receptor Substrate Proteins, Intracellular Signaling Peptides and Proteins, Ligases, MAP Kinase Signaling System, Mice, Morpholines, Multienzyme Complexes, Phosphatidylinositol 3-Kinases, Phosphoproteins, Phosphoric Monoester Hydrolases, Phosphorylation, Proteasome Endopeptidase Complex, Protein Processing, Post-Translational, Protein-Serine-Threonine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-akt, Receptors, Erythropoietin, Ribosomal Protein S6 Kinases, 70-kDa, Signal Transduction, Sirolimus, Transcription Factors, Tumor Suppressor Proteins, Ubiquitin-Protein Ligases
Adaptor Proteins, Signal Transducing, Animals, Apoptosis, Cell Cycle Proteins, Cell Division, Cell Survival, Cells, Cultured, Chromones, Cyclin-Dependent Kinase Inhibitor p27, Cysteine Endopeptidases, DNA-Binding Proteins, Enzyme Activation, Enzyme Inhibitors, Erythroid Precursor Cells, Erythropoietin, Fetal Blood, Forkhead Transcription Factors, Humans, Infant, Newborn, Insulin Receptor Substrate Proteins, Intracellular Signaling Peptides and Proteins, Ligases, MAP Kinase Signaling System, Mice, Morpholines, Multienzyme Complexes, Phosphatidylinositol 3-Kinases, Phosphoproteins, Phosphoric Monoester Hydrolases, Phosphorylation, Proteasome Endopeptidase Complex, Protein Processing, Post-Translational, Protein-Serine-Threonine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-akt, Receptors, Erythropoietin, Ribosomal Protein S6 Kinases, 70-kDa, Signal Transduction, Sirolimus, Transcription Factors, Tumor Suppressor Proteins, Ubiquitin-Protein Ligases
Blood
Date: May. 01, 2003
PubMed ID: 12506011
View in: Pubmed Google Scholar
Download Curated Data For This Publication
194494
Switch View:
- Interactions 5