Phorbol ester-induced reversible inactivation of cytotoxic T cell function: correlation with down-regulation of protein kinase C activity.
When an H-2d-specific cytotoxic T lymphocytes (CTL) clone, FC1, was incubated in the presence of 10(-7) M phorbol myristate acetate (PMA) for 10-12 hr, the cytolytic activity of the CTL against H-2d target cells was abrogated, but was reversibly restored to the normal level after subsequent incubation of the cells in PMA-free medium for more than 10 hr. These effects of PMA have been reported (Russell, J.H.: J. Immunol. 133, 907-912 (1984)), but the mode of its action has not been fully investigated. Here, we analyzed the biochemical basis of the PMA-induced loss of cytolytic activity. Cycloheximide completely blocked the restoration of the PMA-suppressed cytolytic activity, suggesting that protein synthesis was required in this process. PMA-treatment did not affect the levels of CD3 and CD8 molecules expressed on the CTL, nor was the level of a CTL-specific serine esterase, BLT esterase, affected by this treatment. However, the target cell-induced release of BLT esterase from the CTL was suppressed if the cells were pretreated with PMA. PMA-treatment of the CTL led to the down-regulation of protein kinase C (PKC) activity by about 50%. On the other hand, staurosporin, an inhibitor of PKC, completely blocked the target cell lysis when added at 10(-6) M. These results suggest that the down-regulation of at least some isoform(s) of PKC is responsible for the PMA-induced loss of the cytotolytic activity of CTL.
Ohmori
H
H
Department of Biotechnology, Faculty of Engineering, Okayama University, Japan.
Shimada
T
T
Hikida
M
M
Takai
T
T
D000818:Animals; D017252:CD3 Complex / Q000096:biosynthesis; D016827:CD8 Antigens / Q000096:biosynthesis; D003513:Cycloheximide / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects*; D004950:Esterases / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects* / Q000201:enzymology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D017252:CD3 Complex; D016827:CD8 Antigens; D003513:Cycloheximide; D011493:Protein Kinase C; D004950:Esterases; C022635:serine esterase; D013755:Tetradecanoylphorbol Acetate