Interaction of erythropoietin with its type 1 receptor is essential to the development of late erythroid progenitor cells. Through the ectopic expression of receptor mutants in lymphoid and myeloid cell lines, insight has been gained regarding effectors that regulate Epo-induced proliferation. In contrast, effectors that regulate Epo-induced differentiation events (e.g. globin gene expression) are largely undefined. For in vitro studies of this pathway, erythroleukemic SKT6 cell sublines have been isolated which stably and efficiently hemoglobinize in response to Epo. Epo rapidly activated Jak2, STAT5 and detectably STATs 1 and 3, while no effects on GATA-1, EKLF or STAT5 expression were observed. Finally, efficient hemoglobinization of SKT6 cells was shown to be mediated by chimeric receptors comprised of the EGF receptor extracellular domain and truncated cytoplasmic subdomains of either the Epo receptor or the prolactin Nb2 receptor. This work further establishes SKT6 cells as an important model for studies of Epo-stimulated differentiation, and shows that this signaling pathway is promoted by a limited set of membrane-proximal receptor domains and effectors.
