Protein kinase Ctheta activity is involved in the 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced signal transduction pathway leading to apoptosis in L-MAT, a human lymphoblastic T-cell line

FEBS J. 2005 Feb;272(4):903-15. doi: 10.1111/j.1742-4658.2004.04519.x.


The aromatic hydrocarbon receptor (AhR)-dependent pathway involved in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced immunotoxicity has been studied extensively, but the AhR-independent molecular mechanism has not. In previous studies we found that the AhR is not expressed in L-MAT, a human lymphoblastic T-cell line. In this report, we provide the following evidence that the protein kinase C (PKC)theta activity is functionally involved in the AhR-independent signal transduction mechanism that participates in the TCDD-induced L-MAT cell apoptosis. First, only rottlerin, a novel PKC (nPKC)-selective inhibitor, blocked the apoptosis completely, in a dose-dependent manner. Second, PKCtheta was the major nPKC isoform (compared to PKCdelta) expressed in the L-MAT cell line. Third, a cell-permeable myristoylated PKCtheta pseudosubstrate peptide inhibitor also blocked the apoptosis completely, in a dose-dependent manner. Fourth, both rottlerin and myristoylated PKCtheta pseudosubstrate peptide inhibitor completely inhibited PKCtheta kinase activity in vitro at doses that effectively blocked TCDD-induced L-MAT cell apoptosis. TCDD treatment induced a time-dependent activation of nPKC kinase activity in L-MAT cells, and moreover, TCDD induced a translocation of PKCtheta from the cytosolic fraction to the particulate fraction in L-MAT cells. Finally, transient over-expression of a dominant negative PKCtheta (a kinase-dead mutant, K/R 409) in L-MAT cells conferred significant protection against TCDD-induced apoptosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetophenones / pharmacology
  • Apoptosis / drug effects
  • Apoptosis / physiology*
  • Benzopyrans / pharmacology
  • Cell Line, Tumor
  • H-2 Antigens / genetics
  • H-2 Antigens / metabolism
  • Humans
  • Isoenzymes / antagonists & inhibitors
  • Isoenzymes / metabolism*
  • Polychlorinated Dibenzodioxins / metabolism*
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • Protein Kinase C-theta
  • Signal Transduction / physiology*
  • T-Lymphocytes / drug effects
  • T-Lymphocytes / metabolism*
  • Transfection


  • Acetophenones
  • Benzopyrans
  • H-2 Antigens
  • H-2K(K) antigen
  • Isoenzymes
  • Polychlorinated Dibenzodioxins
  • rottlerin
  • PRKCQ protein, human
  • Protein Kinase C
  • Protein Kinase C-theta