title: Disrupted signaling in a mutant J2E cell line that shows enhanced viability, but does not proliferate or differentiate, with erythropoietin.
abstract: The immature erythroid J2E cell line proliferates and terminally differentiates following erythropoietin stimulation. In contrast, the mutant J2E-NR clone does not respond to erythropoietin by either proliferating or differentiating. Here we show that erythropoietin can act as a viability factor for both the J2E and J2E-NR lines, indicating that erythropoietin-initiated maturation is separable from the prevention of cell death. The inability of J2E-NR cells to mature in response to erythropoietin was not due to a defect in the erythropoietin receptor sequence, although surface receptor numbers were reduced. Both the receptor and Janus kinase 2 were phosphorylated after erythropoietin stimulation of J2E-NR cells. However, protein interactions with the erythropoietin receptor and Grb2 were restricted in the mutant cells. Subsequent investigation of several other signaling molecules exposed numerous alterations in J2E-NR cells; phosphorylation changes to phosphatidylinositol 3-kinase, phospholipase Cgamma, p120 GAP, and mitogen-activated protein kinases (p42 and p44) observed in erythropoietin-stimulated J2E cells were not seen in the J2E-NR line. These data indicate that some pathways activated during erythropoietin-induced differentiation may not be essential for the prevention of apoptosis.
authors.affiliation: Department of Biochemistry, University of Western Australia, Australia.
authors.forename: P A
authors.initials: PA
authors.lastname: Tilbrook
authors.forename: T
authors.initials: T
authors.lastname: Bittorf
authors.forename: S J
authors.initials: SJ
authors.lastname: Busfield
authors.forename: D
authors.initials: D
authors.lastname: Chappell
authors.forename: S P
authors.initials: SP
authors.lastname: Klinken
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002087:Butyrates / Q000494:pharmacology; D020148:Butyric Acid; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation; D004921:Erythropoietin / Q000494:pharmacology*; D020690:GTPase-Activating Proteins; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D016296:Mutagenesis; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000032:analysis / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D002087:Butyrates; D020690:GTPase-Activating Proteins; D007527:Isoenzymes; D011506:Proteins; D017467:Receptors, Erythropoietin; D020148:Butyric Acid; D004921:Erythropoietin; D019000:Phosphotyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010738:Type C Phospholipases