M. Grdisa et al., EXPRESSION AND LOSS OF THE TRANSFERRIN RECEPTOR IN GROWING AND DIFFERENTIATING HD3-CELLS, Journal of cellular physiology, 155(2), 1993, pp. 349-357
During induced differentiation and maturation of HD3 cells (a chicken
erythroblast cell line infected with a temperature-sensitive mutant of
the avian erythroblastosis virus), the levels of transferrin receptor
(TFR) and nucleoside transporter increase. Both these activities incr
ease before elevated levels of hemoglobin are detected. Shortly after
induction, as cellular TFR levels rise, a native-size TFR is detected
in the cell-free culture medium, associated with an exosome fraction (
100,000 xg pellet). Nucleoside transporter (measured as NBMPR-binding
activity) is not increased in this pellet with induction. Previous stu
dies have suggested that exosome formation in peripheral reticulocytes
may be a significant route for loss of specific membrane proteins (Jo
hnstone et al., 1 991). Although the present experiments in HD3 cells
do not address the quantitative importance of exosome formation, the s
tudies suggest that exosome formation is an early event in commitment
to the red cell lineage and is not a phenomenon restricted to the term
inal stages of red cell maturation.