Blood, Vol. 92 No. 4 (August 15), 1998:
pp. 1219-1224
The Distal Cytoplasmic Domain of the Erythropoietin Receptor Induces
Granulocytic Differentiation in 32D Cells
Kevin W. Harris,
Xian-Jue Hu,
Suzanne Schultz,
Murat O. Arcasoy,
Bernard G. Forget, and
Nanette Clare
From the South Texas Veterans Health Care System, San Antonio; the
Department of Medicine, Division of Hematology, and Department of
Pathology, University of Texas Health Science Center, San Antonio, TX;
and the Department of Medicine, Hematology Section, Yale University
School of Medicine, New Haven, CT.
The role of hematopoietic growth factors in lineage commitment and
differentiation is unclear. We present evidence that heterologous expression of an erythroid specific receptor allows granulocytic differentiation of a myeloid cell line. We have previously
characterized a truncation mutant of the erythropoietin receptor
(EpoR), which is associated with familial erythrocytosis (Blood
89:4628, 1997). This truncated EpoR lacks the distal 70 amino acids of
the cytoplasmic domain. To study the functional role of this distal
receptor domain, 32D cells, a murine interleukin-3 (IL-3)-dependent
myeloid line, were transfected with the wild-type EpoR (32D/EpoR
WT) or the truncated EpoR (32D/EpoR FE). 32D
cells expressing either the full-length or truncated EpoR display
equivalent proliferative rates in saturating concentrations of Epo.
There is a dramatic difference in maturational phenotype between the
two cell lines, however. The 32D/EpoR FE cells and mock transfected 32D
cells have an immature, monoblastic morphology and do not express the primary granule protein myeloperoxidase. The 32D/EpoR WT cells, on the
other hand, demonstrate granulocytic differentiation with profuse
granulation, mature, clumped chromatin, and myeloperoxidase expression.
There is no evidence of erythroid differentiation in 32D cells
transfected with either the full-length or truncated EpoR. Treatment of
the cells with the specific Jak2 inhibitor tyrphostin AG 490 inhibits
myeloid differentiation driven by the distal EpoR. We conclude that:
(1) the distal cytoplasmic domain of the EpoR is able to induce a
specific myeloid differentiation signal distinct from mitogenic
signaling, and (2) these data extend to myelopoiesis the growing body
of evidence that the cellular milieu, not the specific cytokine
receptor, determines the specificity of differentiation after cytokine
receptor activation.
© 1998 by The American Society of Hematology.
