title: Erythropoietin rapidly reduces phosphorylation of a membrane protein in a murine erythroleukemia cell line.
abstract: Erythropoietin (Epo) is a glycoprotein hormone that specifically regulates the proliferation and differentiation of erythroid progenitor cells. The effect of Epo on the phosphorylation of cellular proteins was investigated in a murine erythroleukemia cell line ELM-I-1 which differentiates to produce hemoglobin in response to Epo. The phosphorylation of a prominent 98 kDa phosphoprotein (pp98) (pI approximately 6.5) in the particulate fraction of ELM-I-1 cells decreased markedly upon exposure of the cells to recombinant human Epo. The effect was rapid and transient, occurring within 1 min after Epo exposure, and disappearing within 15-30 min. Interleukin 3, another hematopoietic factor which is known to act also on erythroid progenitors, did not induce this effect. Phosphoamino acid analysis revealed that pp98 is phosphorylated on serine residues. The results suggest that this rapid and transient alteration in protein phosphorylation may serve as critical trans-membrane signal for Epo.
authors.affiliation: Second Department of Internal Medicine, Kumamoto University Medical School, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Sawada
authors.forename: H
authors.initials: H
authors.lastname: Tsuda
authors.forename: K J
authors.initials: KJ
authors.lastname: Mori
authors.forename: M
authors.initials: M
authors.lastname: Kawakita
authors.forename: K
authors.initials: K
authors.lastname: Takatsuki
mesh_terms: D000818:Animals; D004921:Erythropoietin / Q000494:pharmacology*; D006801:Humans; D007377:Interleukin-3 / Q000494:pharmacology; D004915:Leukemia, Erythroblastic, Acute / Q000473:pathology*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000032:analysis; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction; D014407:Tumor Cells, Cultured / Q000378:metabolism / Q000473:pathology
chemical_list: D007377:Interleukin-3; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; D004921:Erythropoietin; D010768:Phosphoserine; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases