The role of p38 kinase in the activation of the premature senescence program in transformed mouse fibroblasts

Abstract

The role of p38α stress-kinase in the regulation of the premature senescence program induced by the histone deacetylase inhibitor sodium butyrate (NaB) was studied in rodent transformed cell lines. The study was carried out on E1A+cHa-ras transformants obtained from mouse embryonic fibroblasts null for the Mapk14 gene encoding p38α stress-kinase (the mERasp38−/− cell line), or for the PPM1D gene encoding the Wip1 phosphatase (the mERas Wip1−/− cell line), whose absence led to constitutive activation of p38α kinase. It was found that after NaB treatment both cell lines completely stopped proliferation due to irreversible G1/S cell cycle arrest. In both lines a marker of senescence appeared—the activity of β-galactosidase (SA-β-Gal). As well, treatment of the cells with NaB for several days led to morphological cell changes, such as partial readjustment of the actin cytoskeleton, spreading on the substrate, and heterochromatin focus formation (SAHF) in the senescent cell nuclei. These data allow us to suggest that, in the absence of functionally active p38α kinase, the NaB-induced irreversible process of cellular senescence may occur via alternative pathways for downregulation of the cell cycle.