J. Biol. Chem., Vol. 261, Issue 19, 8734-8737, Jul, 1986
The effect of prostaglandin E2 (PGE2) on amino acid uptake and protein formation by lung fibroblasts
RH Goldstein, S Sakowski, D Meeker, C Franzblau and P Polgar
The effect of prostaglandin E2 (PGE2) on the utilization of extracellular
amino acids by fetal lung fibroblasts was examined. PGE2 decreased the
uptake of proline and aminoisobutyric acid (AIB) by quiescent fibroblasts
in culture. The uptake of AIB by serum-activated cultures was also
dramatically decreased by PGE2. The PGE2-induced decrease in the uptake of
AIB was first observed at 4 h following the addition of the effector
molecule to the cultures. PGE2 did not affect the uptake of leucine. The
addition of cycloheximide also resulted in a decrease in the uptake of
proline, similar to that induced by PGE2 at 5 X 10(-8) M. The combination
of cycloheximide and PGE2 resulted in a further decrease in proline uptake.
Kinetic analysis of AIB uptake following a 24-h PGE2 treatment showed an
increase in the apparent Km as compared with untreated cultures. The
prostaglandin remained active for at least 72 h after the addition of the
molecule. Removal of the PGE2 was followed by an influx of proline into the
cells. The decrease in proline uptake was associated with a decrease in the
amount of intracellular free proline and an overall decrease in the amount
of cell-associated protein. While PGE2 is known to increase intracellular
protein degradation, the effect of PGE2 on amino acid uptake was not the
result of an increase in the intracellular concentration of amino acids
(transinhibition).