Induction of the differentiation of HL-60 cells by phorbol 12-myristate 13-acetate activates a Na(+)-dependent uridine-transport system. Involvement of protein kinase C.
The Na(+)-dependent transport and facilitated diffusion of uridine were measured after differentiation of HL-60 leukaemia cells along the monocytic pathway by phorbol 12-myristate 13-acetate (PMA). PMA (200 ng/ml) caused a marked increase in Na(+)-dependent uridine transport within 48 h of exposure that was attributable to an increase in transport affinity (apparent Km values of 1.15 +/- 0.22 and 44 +/- 4.4 microM for PMA-induced and uninduced cells respectively), with no change in Vmax. (0.15 +/- 0.02 and 0.13 +/- 0.01 pmol/s per microliter of cell water for PMA-induced and uninduced cells respectively). A corresponding rapid decrease in both the rate of facilitated diffusion and the formation of uracil nucleotides occurred in PMA-induced cells. As a consequence of these changes, intracellular pools of uridine 3-4-fold greater than those in the medium were generated. A similar increase in Na(+)-dependent transport of adenosine, inosine, guanosine, thymidine and cytidine (Km values of 1-4 microM) was observed. The effects of PMA on the activation of the Na(+)-dependent uridine transporter were inhibited by staurosporine, suggesting the involvement of protein kinase C. The findings indicate that a change in the balance of the cellular mechanisms employed for nucleoside transport occurs during the monocytic differentiation of HL-60 leukaemia cells.
Lee
C W
CW
Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510.
Sokoloski
J A
JA
Sartorelli
A C
AC
Handschumacher
R E
RE
D000470:Alkaloids / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D002460:Cell Line; D006801:Humans; D007700:Kinetics; D015473:Leukemia, Promyelocytic, Acute; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012263:Ribonucleosides / Q000378:metabolism; D012964:Sodium / Q000494:pharmacology*; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014529:Uridine / Q000378:metabolism*
D000470:Alkaloids; D012263:Ribonucleosides; D012964:Sodium; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; D014529:Uridine