Differential effects of protein kinase C activation on calcium storage and capacitative calcium entry in NIH 3T3 cells.
In NIH 3T3 cells, treatment with phorbol 12-myristate 13-acetate (PMA) reduced the release of Ca2+ by thapsigargin, but did not activate Ca2+ entry; Ca2+ influx was triggered after the residual pool was emptied by thapsigargin, and this Ca2+ influx was similar to that induced by thapsigargin in control cells. The effect of PMA was due to decreased Ca2+ storage because 1) Ca2+ release by ionomycin was similarly affected by PMA, and in both control and PMA-treated cells, ionomycin did not release Ca2+ following thapsigargin treatment; 2) PMA reduced 45Ca2+ accumulation; and 3) studies with Ca2+ indicator compartmentalized into the endoplasmic reticulum indicated that stored Ca2+ was reduced by PMA. Although PMA did not itself activate Ca2+ entry, PMA potentiated Ca2+ entry with low concentrations of cyclopiazonic acid. With a somewhat higher concentration of cyclopiazonic acid, PMA had no effect on calcium entry. Thus, protein kinase C has two apparent actions on calcium signaling in NIH 3T3 cells: 1) reduced intracellular Ca2+ storage capacity and 2) augmented calcium entry with submaximal intracellular Ca2+ pool depletion. These actions indicate a complex and potentially important role for the protein kinase C system in calcium homeostasis in this cell type.
Ribeiro
C M
CM
NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
Putney
J W
JW
D016475:3T3 Cells; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006706:Homeostasis; D007211:Indoles / Q000494:pharmacology; D017136:Ion Transport; D051379:Mice; D011493:Protein Kinase C / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin
D004791:Enzyme Inhibitors; D007211:Indoles; D013729:Terpenes; D019284:Thapsigargin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; C000543:cyclopiazonic acid