Characterization of specific functional receptors for HuIFN-alpha on a human megakaryocytic cell line (Dami): expression related to differentiation.
Interferon-alpha (IFN-alpha) treatment has been shown to be highly effective in inhibiting human megakaryocytopoiesis and controlling thrombocytosis in patients with myeloproliferative disorders. These observations suggest that IFN-alpha might play some role in the biological feature of the megakaryocytic lineage and led us to investigate the presence of specific receptors for IFN-alpha on human megakaryocytic cells, i.e. the Dami cell line, and to study the regulation of their expression. Our study demonstrates that [125I]-recombinant human IFN-alpha ([125I]rHu-IFN-alpha) binds to high-affinity specific receptor on these cells. Scatchard analysis of binding data indicates the presence of homogeneous binding sites estimated in the range of 3000-5000, with an apparent equilibrium dissociation constant, Kd, of 1-2 x 10(-9) M. Also, [125I]rHuIFN-alpha binding capacity decreased in Dami cells incubated with unlabelled rHuIFN-alpha. This down-regulation which was dose-dependent appeared to result from a reduction of IFN-alpha cell surface receptors and was observed at doses that elicited antiproliferative effects in Dami cells. Cross-linking of [125I]rHuIFN-alpha to Dami membrane proteins using a bifunctional reagent yielded to a radioactive complex of approximately 150,000 kD on SDS-PAGE. Furthermore, in response to PMA, which induces the differentiation/maturation of the Dami cells as evaluated by surface marker and ploidy analysis, a 3-fold increase of the number of specific membrane receptors for IFN-alpha was observed, without any modification of either the affinity or the M(r) value of the cross-linked complex. Such an increase appeared to be restricted to IFN-alpha receptors; actually it was not observed in [125I]IFN-gamma binding experiments. Transcript analysis indicated that down-regulation and increased expression of the IFN-alpha receptor after PMA treatment are post-transcriptional events.
Martyré
M C
MC
Unité 365 INSERM, Institut Curie, Section de Biologie, France.
Wietzerbin
J
J
D000954:Antigens, Surface / Q000032:analysis / Q000187:drug effects; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D006801:Humans; D016898:Interferon-alpha / Q000378:metabolism*; D008533:Megakaryocytes / Q000166:cytology / Q000378:metabolism*; D011003:Ploidies; D017471:Receptors, Interferon / Q000032:analysis* / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000954:Antigens, Surface; D016898:Interferon-alpha; D017471:Receptors, Interferon; D013755:Tetradecanoylphorbol Acetate