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Protein kinase Cθ 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
Author(s) -
Ahmed Sohel,
Shibazaki Masahiko,
Takeuchi Takashi,
Kikuchi Hideaki
Publication year - 2005
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2004.04519.x
Subject(s) - rottlerin , protein kinase c , apoptosis , signal transduction , microbiology and biotechnology , cell culture , biology , cytosol , protein kinase a , kinase , chemistry , biochemistry , enzyme , genetics
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)θ 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, PKCθ was the major nPKC isoform (compared to PKCδ) expressed in the L‐MAT cell line. Third, a cell‐permeable myristoylated PKCθ pseudosubstrate peptide inhibitor also blocked the apoptosis completely, in a dose‐dependent manner. Fourth, both rottlerin and myristoylated PKCθ pseudosubstrate peptide inhibitor completely inhibited PKCθ 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 PKCθ from the cytosolic fraction to the particulate fraction in L‐MAT cells. Finally, transient over‐expression of a dominant negative PKCθ (a kinase‐dead mutant, K/R 409) in L‐MAT cells conferred significant protection against TCDD‐induced apoptosis.