MURINE ERYTHROPOIETIN--RESPONSE AND RECEPTORS

重组人促红细胞生成素（rEpo）已经成熟

Recombinant human Epo (rEpo) has become available and procedures have been developed whereby erythroid progenitor cells of several provenances can be harvested in near purity. Our preliminary studies of Epo-reception by ca. 80%-pure murine erythroid colony-forming units (CFUe) and by the S8 murine erythroleukemia (MEL) cell line, together with collateral studies by others of purified spleen cells derived from mice infected with the anemia-strain of Friend virus (FVA), indicate that there are at least two kinds of erythropoietin receptors (EpoR): one with a dissociation constant (Kd) of approximately 40 pM, the other with Kd of approximately 400 pM. Conditioned by our repeated observation that erythroid maturation can be atypical in virus- infected cells, we hypothesize that (i) high-affinity (approximately 40 pM) EpoR is either a viral import or one regulated by virus transformation and (ii) low-affinity (approximately 400 pM) EpoR is the one naturally expressed in mouse CFUe. Our intent is to verify/falsify these hypotheses and, concurrently, answer questions arising from preliminary studies of Epo-response by CFUe and from studies of EpoR biology in CFUe and S8-MEL-cells. We hope thereby to clarify the temporal relationship between Epo-addition and globin gene response; resolve the mystery of why CFUe-EpoR sites seem abundant far beyond functional needs; establish some ways in which EpoR can be regulated; refine our understanding of physical features and fate of EpoR, including confirmation/rejection of the possibility that Epo and/or EpoR is bound to DNA or chromatin in S8-MEL cells; in a large-scale undertaking, apply affinity methods to the isolation of EpoR and immunological methods to the isolation of recombinant cDNA clones encoding it; and, in a brisk but short- lived undertaking, isolate cDNA for "early-response" genes whose expression depends upon Epo and, thereafter, use arising cDNA clones to examine heretofore unknown aspects of Epo-responses by the several EpoR.