ABSTRACT
A key regulator of cellular senescence, mTORC1 complex, is the target of many signaling cascades including Ras/Raf/MEK/ERK-signaling cascade. In this paper we investigated the role of MEK/ERK-branch of this cascade in the process of cellular senescence induced by histone deacetylase inhibitor (HDACI) sodium butyrate (NaBut), in transformed rat embryo fibroblasts. Suppression of MEK/ERK activity by inhibitor PD0325901 does not prevent activation of mTORC1 complex induced by NaBut treatment. After the suppression of MEK/ERK, activity of mTORC1 increased as well as complex mTORC2. Activation of mTOR-containing complexes accompanied by the reorganization of the actin cytoskeleton with the formation of actin stress fibers and the appearance of some markers of cellular senescence. In contrast to NaBut-induced senescence accumulation of proteins was not observed, which may be due to increased activity of the degradation processes. Furthermore, the induction of senescence in conditions suppressed MEK/ERK leads to a drastic decrease in cell viability. Thus, NaBut-induced senescence upon suppressed activity of MEK/ERK-branch of MAP kinase cascade has a more pronounced tumor-suppressor effect associated with stronger activation of both mTOR-complexes, reorganization of the actin cytoskeleton and protein degradation.
Subject(s)
Cellular Senescence/genetics , Fibroblasts/metabolism , Histone Deacetylase 1/genetics , Mitogen-Activated Protein Kinase 1/genetics , Mitogen-Activated Protein Kinase 3/genetics , Actin Cytoskeleton/drug effects , Actin Cytoskeleton/ultrastructure , Animals , Benzamides/pharmacology , Butyric Acid/pharmacology , Cell Line, Transformed , Cell Survival/drug effects , Cellular Senescence/drug effects , Diphenylamine/analogs & derivatives , Diphenylamine/pharmacology , Embryo, Mammalian , Fibroblasts/drug effects , Fibroblasts/ultrastructure , Gene Expression Regulation , Histone Deacetylase 1/antagonists & inhibitors , Histone Deacetylase 1/metabolism , Histone Deacetylase Inhibitors/pharmacology , Mechanistic Target of Rapamycin Complex 1 , Mechanistic Target of Rapamycin Complex 2 , Mitogen-Activated Protein Kinase 1/antagonists & inhibitors , Mitogen-Activated Protein Kinase 1/metabolism , Mitogen-Activated Protein Kinase 3/antagonists & inhibitors , Mitogen-Activated Protein Kinase 3/metabolism , Multiprotein Complexes/genetics , Multiprotein Complexes/metabolism , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins p21(ras)/genetics , Proto-Oncogene Proteins p21(ras)/metabolism , Rats , Signal Transduction , TOR Serine-Threonine Kinases/genetics , TOR Serine-Threonine Kinases/metabolismABSTRACT
We studied the role of p38 kinase and JNK1,2 in the activation of the complex mTORC1 and the program of senescence induced by histone deacetylase inhibitor, sodium butyrate (NaBut), in mouse embryonic fibroblasts transformed by E1A+cHa-Ras oncogenes. It was found that transformants from knockouts for the genes p38, were able to implement the program of NaBut-induced senescence, according to the data of the cell cycle arrest, inhibition of proliferation, hypertrophic changes associated with the activation of mTORC1 and SA-beta-galactosidase activity. According to the behavior of these markers, cell knockouts for the genes jnk1,2 were unable to implement NaBut-induced senescence. Induction of senescence closely correlates with the activation of the complex mTORC1, as it was shown by inhibiting mTORC1 with rapamycin. We believe that JNK 1,2 kinases are required for mTORC1 activation and acquiring the markers of premature senescence, induced by NaBut in the E1A+cHa-Ras transformants.
