title: Macrophage-stimulating protein cooperates with erythropoietin to induce colony formation and MAP kinase activation in primary erythroid progenitor cells.
abstract: We have shown that Fv2, the Friend virus susceptibility 2 locus, encodes a naturally occurring amino-terminally truncated form of the STK receptor tyrosine kinase (Sf-Stk). Sf-Stk appears to interact with the viral glycoprotein gp55 and drive erythropoietin (Epo)-independent expansion of Friend virus-infected erythroblasts. Presumably, Sf-Stk provides signals that cooperate with EpoR signaling to induce the polyclonal expansion of infected cells. In this report, we show that macrophage-stimulating protein (MSP), the ligand for full-length STK, can also cooperate with Epo to enhance burst-forming units-erythroid (BFU-E) formation. To evaluate the signals induced by MSP/STK in primary erythroid progenitor cells, we adapted a method for the expansion of murine bone marrow mononuclear cells. The expanded progenitor cells express STK and respond to MSP in a colony assay. Furthermore, we demonstrate that low doses of MSP and Epo stimulation of the expanded cells cooperate to induce the phosphorylation of MAP kinase. Using the MEK inhibitor PD98059, we show that the activation of ERK is required for the enhanced BFU-E formation in response to MSP. These findings suggest that MSP has the ability to enhance erythroid colony formation in response to Epo, and that this response is dependent on the ability of MSP to induce the MAP kinase pathway.
authors.affiliation: Graduate Program in Pathobiology, Department of Veterinary Science, Pennsylvania State University, University Park 16802, USA.
authors.forename: Hami E
authors.initials: HE
authors.lastname: Teal
authors.forename: Anamaria
authors.initials: A
authors.lastname: Craici
authors.forename: Robert F
authors.initials: RF
authors.lastname: Paulson
authors.forename: Pamela H
authors.initials: PH
authors.lastname: Correll
mesh_terms: D000818:Animals; D001853:Bone Marrow; D001854:Bone Marrow Cells; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D004920:Erythropoiesis / Q000187:drug effects; D004921:Erythropoietin / Q000494:pharmacology*; D017228:Hepatocyte Growth Factor / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D011518:Proto-Oncogene Proteins; C082332:macrophage stimulating protein; D004921:Erythropoietin; D017228:Hepatocyte Growth Factor; D020928:Mitogen-Activated Protein Kinases