Receptors for the hematopoietic growth factors erythropoietin, interleukin 3 (IL-3), and granulocyte-macrophage colony-stimulating factor (GM-CSF) are members of a structurally related receptor superfamily. Interestingly, while none of these receptors encode tyrosine kinase activities, induced tyrosine phosphorylation has been observed in various responsive cells stimulated with each factor. Toward defining possible common transduction pathways which are activated by these three cytokines, we have studied induced protein phosphorylation in murine myeloid FDC-P1 cells stably transfected with an erythropoietin receptor cDNA (FDC-ER cells). FDC-ER cells proliferate in response to erythropoietin (Quelle, D. E., and Wojchowski, D. M. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 4801-4805), and presently are shown to rapidly phosphorylate a M(r) 100,000 cytosolic protein (pp100) at tyrosine residues in response to this factor. Phosphorylation of pp100 also is induced in FDC-P1 and FDC-ER cells in response to IL-3 or GM-CSF. Importantly, quantitative analyses showed identical concentration dependencies for factor-induced pp100 phosphorylation and induced cell proliferation. Moreover, a selective loss of proliferative responsiveness to GM-CSF in FDC-ER cells was associated with a reduced capacity of GM-CSF to induce pp100 phosphorylation. Finally, limited differences in tryptic phosphopeptide maps of pp100 as isolated following exposure to erythropoietin, IL-3, or GM-CSF were observed, suggesting that these factors also may preferentially induce phosphorylation of pp100 at distinct sites. These findings are consistent with a role for pp100 as a common cytosolic transducer in the apparently convergent pathways of erythropoietin-, IL-3-, and GM-CSF-induced proliferation of myeloid progenitor cells.
