O. Bussolati et al., THE RELATIONSHIP BETWEEN SODIUM-DEPENDENT TRANSPORT OF ANIONIC AMINO-ACIDS AND CELL-PROLIFERATION, Biochimica et biophysica acta, 1151(2), 1993, pp. 153-160
The relationship between the transport of anionic amino acids and the
proliferative status of the cell population has been studied in NIH-3T
3 cells. Proliferative quiescence, verified by determinations of growt
h-rate quotient and incorporation of thymidine, is associated with a m
arked increase of the influx of L-aspartate. After 7-10 days of serum
starvation, the initial influx of L-aspartate increases by 8-10-times
with respect to the transport activity determined in growing cells. Th
e operational properties of the influx of L-aspartate are similar in g
rowing and quiescent cells; in particular, the influx of the anionic a
mino acid is mostly Na+-dependent and completely suppressed by an exce
ss Of L-glutamate and D-aspartate, but not of D-glutamate. These featu
res suggest that, in both cases, aspartate uptake occurs through syste
m X(AG)-. The quiescence-related increase in aspartate transport is gr
adual, sensitive to the inhibition of protein synthesis and referable
to the enhanced maximal capacity of transport system X(AG)-. Restorati
on of serum concentration in the culture medium of serum-starved cells
causes a decrease in aspartate transport that is maximal in correspon
dence to late G1/S phases. It is concluded that the X(AG)- system for
anionic amino-acid uptake is sensitive to the proliferative status of
the cell population and that, in particular, its transport activity is
stimulated by the establishment of proliferative quiescence.