A role for protein kinase CbetaI in the regulation of Ca2+ entry in Jurkat T cells.
T cell activation leading to cytokine production and cellular proliferation involves a regulated increase and subsequent decrease in the intracellular concentration of Ca2+ ([Ca2+]i). While much is understood about agonist-induced increases in [Ca2+]i, less is known about down-regulation of this pathway. Understanding the mechanism of this down-regulation is critical to the prevention of cell death that can be the consequence of a sustained elevation in [Ca2+]i. Protein kinase C (PKC), activated by the diacylglycerol produced as a consequence of T cell receptor engagement, has long been presumed to be involved in this down-regulation, although the precise mechanism is not wholly clear. In this report we demonstrate that activation of PKC by phorbol esters slightly decreases the rate of Ca2+ efflux from the cytosol of Jurkat T cells following stimulation through the T cell receptor or stimulation in a receptor-independent manner by thapsigargin. On the other hand, phorbol ester treatment dramatically reduces the rate of Ca2+ influx following stimulation. Phorbol ester treatment is without an effect on Ca2+ influx in a different T cell line, HSB. Down-regulation of PKCbetaI expression by 18-h phorbol ester treatment is associated with a loss of the response to acute phorbol ester treatment in Jurkat cells, suggesting that PKCbetaI may be the isozyme responsible for the effects on Ca2+ influx. Electroporation of an anti-PKCbetaI antibody, but not antibodies against PKCalpha or PKCgamma, led to an increase in the rate of Ca2+ influx following stimulation. Taken together, these data suggest that PKCbetaI may be a component of the down-regulation of increases in [Ca2+]i associated with Jurkat T cell activation.
Haverstick
D M
DM
Department of Pathology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA. dmh2t@virginia.edu
Dicus
M
M
Resnick
M S
MS
Sando
J J
JJ
Gray
L S
LS
D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D006801:Humans; D017136:Ion Transport; D019169:Jurkat Cells; D007700:Kinetics; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D013601:T-Lymphocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D002121:Calcium Channel Blockers; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium