Characterization of a novel form of transferrin receptor preferentially
expressed on normal erythroid progenitors and precursors
T Cotner, AD Gupta, T Papayannopoulou and G Stamatoyannopoulos
Department of Pediatrics, University of Washington, Seattle.
A panel of monoclonal antibodies (MoAbs) against cell surface proteins of
early BFUe progeny was characterized. Five of these antibodies (Abs)
reacted with normal erythroid, but not myeloid, bone marrow cells. Each of
the five antibodies, typified by Ab 69.20, immunoprecipitated a dimeric
complex of 185,000, which is composed of two identical disulfide-bonded
subunits. This antigen had affinity for transferrin, and was essentially
identical in biochemical characteristics to transferrin receptors
precipitated with the well-characterized MoAbs OKT9 and 5E9. However, this
form of transferrin receptor lacked both the OKT9 and 5E9 antigenic
determinants and, moreover, the 69.20 epitope was absent from the
conventional transferrin receptor, as defined by Abs OKT9 and 5E9.
Modulation experiments demonstrated that both 69.20 and OKT9 modulated
large, virtually independent populations of transferrin receptors. Both
forms of transferrin receptor appeared to be derived from the product of a
single gene, but the form defined by MoAb 69.20 apparently predominates in
cells of the erythroid lineage and some transformed cell types that
manifest a special requirement for iron. These data suggest that cells with
a high iron requirement synthesize two forms of transferrin receptor,
possibly by means of differential mRNA splicing or by posttranslational
modification of the transferrin receptor.
Volume 73,
Issue 1,
pp. 214-221,
01/01/1989
Copyright © 1989 by The American Society of Hematology
