title: Identification of a novel pathway important for proliferation and differentiation of primary erythroid progenitors.
abstract: Homodimerization of the erythropoietin (EPO) receptor (EPO-R) in response to EPO binding transiently activates the receptor-associated protein tyrosine kinase JAK2. Tyrosine phosphorylation of the EPO-R creates "docking sites" for SH2 domain(s) in signaling molecules such as the protein tyrosine phosphatases SH-PTP1 and SH-PTP2, phosphoinositide 3-kinase (PI3 kinase), and STAT5. However, little is known about the specific intracellular signals essential for proliferation and differentiation of erythroid progenitors. Here we show that an EPO-R containing only one cytosolic (phospho)tyrosine residue, Y479, induces a signal transduction pathway sufficient for proliferation and differentiation of fetal liver progenitors of erythroid colony-forming units from EPO-R(-/-) mice as well as for proliferation of cultured hematopoietic cells. This cascade involves sequential EPO-induced recruitment of PI3 kinase to the EPO-R and activation of mitogen-activated protein kinase activity, independent of the Shc/Grb2-adapter pathway and of STAT5. Protein kinase C epsilon may be one of the mediators connecting PI3 kinase with the mitogen-activated protein kinase signaling cascade. Our results identify a signaling cascade important in vivo for erythroid cell proliferation and differentiation.
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
authors.forename: U
authors.initials: U
authors.lastname: Klingmüller
authors.forename: H
authors.initials: H
authors.lastname: Wu
authors.forename: J G
authors.initials: JG
authors.lastname: Hsiao
authors.forename: A
authors.initials: A
authors.lastname: Toker
authors.forename: B C
authors.initials: BC
authors.lastname: Duckworth
authors.forename: L C
authors.initials: LC
authors.lastname: Cantley
authors.forename: H F
authors.initials: HF
authors.lastname: Lodish
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D004789:Enzyme Activation; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000378:metabolism*; D004921:Erythropoietin / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D051744:Protein Kinase C-epsilon; D017467:Receptors, Erythropoietin / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D017467:Receptors, Erythropoietin; D004921:Erythropoietin; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); C497256:Prkce protein, mouse; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D017871:Calcium-Calmodulin-Dependent Protein Kinases