Alteration of the PKC theta-Vav1 complex and phosphorylation of Vav1 in TCDD-induced apoptosis in the lymphoblastic T cell line, L-MAT.
We have previously reported that protein kinase C (PKC) theta (theta) and protein tyrosine kinase are involved in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced apoptosis of L-MAT, a human lymphoblastic T cell line. In the current report, we show that Vav1, a GDP/GTP exchange factor for Rho-like small GTPases, could be detected by Western blotting in the membrane fraction of L-MAT cells after TCDD treatment and was precipitated by incubating with an antibody against PKC theta. Furthermore, the degree of phosphorylation of Vav1, which can be detected using the phosphotyrosine-specific antibody PY-20 or 4G10, is significantly increased after treatment with TCDD. In addition, pretreatment of the cells with genistein, a protein tyrosine kinase inhibitor, abolished the phosphorylation of Vav1 and inhibited the apoptosis. These results suggest that TCDD treatment may activate an unidentified protein tyrosine kinase. Accordingly we hypothesize that this kinase phosphorylates Vav1, following which phosphorylated Vav1 may translocate to the membrane with PKC theta. Finally, PKC theta may mediate the transfer of the apoptotic signal to downstream components.
Ishida
Masato
M
Division of Cell Technology, Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan. onigiri atatamemasuka@hotmail.co.jp
Itsukaichi
Takeo
T
Kobayashi
Daisuke
D
Kikuchi
Hideaki
H
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002461:Cell Line, Transformed; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism*; D011817:Rabbits; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D007527:Isoenzymes; D000072317:Polychlorinated Dibenzodioxins; D051567:Proto-Oncogene Proteins c-vav; C496618:VAV1 protein, human; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta