title: 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.
abstract: 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.
authors.affiliation: Department of Molecular Genetics, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
authors.forename: Sohel
authors.initials: S
authors.lastname: Ahmed
authors.forename: Masahiko
authors.initials: M
authors.lastname: Shibazaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Takeuchi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kikuchi
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001578:Benzopyrans / Q000494:pharmacology; D045744:Cell Line, Tumor; D006183:H-2 Antigens / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection
chemical_list: D000098:Acetophenones; D001578:Benzopyrans; D006183:H-2 Antigens; C024755:H-2K(K) antigen; D007527:Isoenzymes; D000072317:Polychlorinated Dibenzodioxins; C085746:rottlerin; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta