TAILIEUCHUNG - Báo cáo khoa học: Protein kinase Ch activity is involved in the 2,3,7,8tetrachlorodibenzo-p-dioxin-induced signal transduction pathway leading to apoptosis in L-MAT, a human lymphoblastic T-cell line

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 mechan-ism 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)hactivity is func-tionally involved in the AhR-independent signal transduction mechanism that participates in the TCDD-induced L-MAT cell apoptosis | ềFEBS Journal Protein kinase Cỡ 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 Sohel Ahmed Masahiko Shibazaki Takashi Takeuchi and Hideaki Kikuchi Department of Molecular Genetics Institute of Development Aging and Cancer Tohoku University Sendai Japan Keywords dioxin apoptosis PKC6 lymphoblastic T cell rottlerin Correspondence H. Kikuchi Department of Biochemistry and Biotechnology Faculty of Agriculture and Life Science Hirosaki University 3 Bunkyo-cho Hirosaki 036-8561 Japan Fax 81 172 39 3586 Tel 81 172 39 3586 E-mail hkikuchi@ Received 17 June 2004 revised 7 September 2004 accepted 8 December 2004 doi 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 h 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 PKCh was the major nPKC isoform compared to PKCỖ expressed in the L-MAT cell line. Third a cell-permeable myristoylated PKCh pseudosubstrate peptide inhibitor also blocked the apoptosis completely in a dose-dependent manner. Fourth both rottlerin and myristoylated PKCh pseudosubstrate peptide inhibitor completely inhibited PKC0 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

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