title: Functional interaction of erythropoietin and stem cell factor receptors is essential for erythroid colony formation.
abstract: Production of mature erythrocytes requires multiple growth factors, but we do not know how their actions are coordinated. Here we show that erythroid progenitors from erythropoietin receptor (Epo-R)-/- fetal livers, infected in vitro with a retrovirus expressing the wild-type Epo-R, require addition of both Epo and stem cell factor (SCF) to form colony-forming unit erythroid (CFU-E) colonies. Thus, a functional interaction between KIT and the Epo-R, similar to what we reported in cultured cells, is essential for the function of CFU-E progenitors. In contrast, CFU-E colony formation in vitro by normal fetal liver progenitors requires only Epo; the essential interaction between activated KIT and the Epo-R must have occurred in vivo before or at the CFU-E progenitor stage. Using truncated dominant-negative mutant Epo-Rs, we show that KIT does not activate the Epo-R by inducing its dimerization, but presumably does so by phosphorylating tyrosine residue(s) in its cytosolic domain. By expressing mutant Epo-Rs containing only one of eight cytosolic tyrosines, we show that either tyrosine residue Y464 or Y479 suffices for Epo-dependent cell proliferation. However, only Epo-R F7Y479 is capable of supporting erythroid colony formation when expressed in (Epo-R)-/- fetal liver cells, indicating that Y464 either cannot send a differentiation signal or fails to respond to SCF/KIT activation. This work employs a novel experimental system to study the function of growth factors and their receptors in normal hematopoiesis.
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
authors.forename: H
authors.initials: H
authors.lastname: Wu
authors.forename: U
authors.initials: U
authors.lastname: Klingmüller
authors.forename: A
authors.initials: A
authors.lastname: Acurio
authors.forename: J G
authors.initials: JG
authors.lastname: Hsiao
authors.forename: H F
authors.initials: HF
authors.lastname: Lodish
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002455:Cell Division; D003593:Cytoplasm / Q000378:metabolism; D019281:Dimerization; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000378:metabolism*; D004920:Erythropoiesis / Q000502:physiology*; D004921:Erythropoietin / Q000378:metabolism / Q000494:pharmacology; D005333:Fetus / Q000378:metabolism; D005786:Gene Expression Regulation; D008099:Liver / Q000196:embryology; D051379:Mice; D008815:Mice, Inbred Strains; D010766:Phosphorylation; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D017467:Receptors, Erythropoietin / Q000737:chemistry / Q000378:metabolism*; D019089:Stem Cell Factor / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism
chemical_list: D017467:Receptors, Erythropoietin; D019089:Stem Cell Factor; D004921:Erythropoietin; D014443:Tyrosine; D019009:Proto-Oncogene Proteins c-kit