Possible role of Na+ influx in phorbol ester‐induced down‐regulation of protein kinase C in HL60 cells

[摘要]

Amiloride, an inhibitor of Na⁺/H⁺ exchange, inhibited down-regulation of protein kinase C in HL60 cells induced by tumor-promoting phorbol ester in dose-dependent manner judging from immunoblot analysis. This inhibition was observed with regard to type I (γ), type II (β), and type III (α) isozymes of protein kinase C. On the other hand, monensin, a Na⁺ ionophore, accelerated the down-regulation of protein kinase C induced by phorbol ester. When we examined ²²Na⁺ uptake by HL60 cells, the higher uptake was observed after stimulation with phorbol ester compared to the control cells and this ²²Na⁺ uptake was strongly inhibited by the addition of amiloride. However, monensin further stimulated the ²²Na⁺ uptake observed in phorbol ester-treated cells. These data suggest that the increase in intracellular Na⁺ concentration may be one of the triggers for the induction of down regulation of protein kinase C.

[学科分类] 生物化学/生物物理

[关键词] Protein kinase C;Down-regulation;Na+/H+ exchanger;HL60 cell;PKC;protein kinase C;TPA;12-O-tetradecanoylphorbol 13-acetate;SDS-PAGE;sodium dodecyl sulfate-polyacrylamide gel electrophoresis;TPBS;phosphate-buffered saline containing 0.05% Tween 20