title: HS1 interacts with Lyn and is critical for erythropoietin-induced differentiation of erythroid cells.
abstract: Erythroid cells terminally differentiate in response to erythropoietin binding its cognate receptor. Previously we have shown that the tyrosine kinase Lyn associates with the erythropoietin receptor and is essential for hemoglobin synthesis in three erythroleukemic cell lines. To understand Lyn signaling events in erythroid cells, the yeast two-hybrid system was used to analyze interactions with other proteins. Here we show that the hemopoietic-specific protein HS1 interacted directly with the SH3 domain of Lyn, via its proline-rich region. A truncated HS1, bearing the Lyn-binding domain, was introduced into J2E erythroleukemic cells to determine the impact upon responsiveness to erythropoietin. Truncated HS1 had a striking effect on the phenotype of the J2E line-the cells were smaller, more basophilic than the parental proerythoblastoid cells and had fewer surface erythropoietin receptors. Moreover, basal and erythropoietin-induced proliferation and differentiation were markedly suppressed. The inability of cells containing the truncated HS1 to differentiate may be a consequence of markedly reduced levels of Lyn and GATA-1. In addition, erythropoietin stimulation of these cells resulted in rapid, endosome-mediated degradation of endogenous HS1. The truncated HS1 also suppressed the development of erythroid colonies from fetal liver cells. These data show that disrupting HS1 has profoundly influenced the ability of erythroid cells to terminally differentiate.
authors.affiliation: Laboratory for Cancer Medicine, Department of Biochemistry, the University of Western Australia and Royal Perth Hospital, WA 6001, Western Australia, Australia.
authors.forename: E
authors.initials: E
authors.lastname: Ingley
authors.forename: M K
authors.initials: MK
authors.lastname: Sarna
authors.forename: J G
authors.initials: JG
authors.lastname: Beaumont
authors.forename: P A
authors.initials: PA
authors.lastname: Tilbrook
authors.forename: S
authors.initials: S
authors.lastname: Tsai
authors.forename: Y
authors.initials: Y
authors.lastname: Takemoto
authors.forename: J H
authors.initials: JH
authors.lastname: Williams
authors.forename: S P
authors.initials: SP
authors.lastname: Klinken
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D011992:Endosomes / Q000378:metabolism; D015672:Erythroid Precursor Cells / Q000166:cytology* / Q000187:drug effects; D004921:Erythropoietin / Q000494:pharmacology*; D004915:Leukemia, Erythroblastic, Acute; D010446:Peptide Fragments / Q000494:pharmacology; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014407:Tumor Cells, Cultured; D020798:Two-Hybrid System Techniques; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001798:Blood Proteins; C061909:HCLS1 protein, human; D010446:Peptide Fragments; D004921:Erythropoietin; D019061:src-Family Kinases