Glutathione S-transferase pi localizes in mitochondria and protects against oxidative stress.

Glutathione S-transferases (GSTs) are multifunctional enzymes involved in the protection of cellular components against anti-cancer drugs or peroxidative stress. Previously we found that GST pi, an isoform of the GSTs, is transported into the nucleus. In the present study, we found that GST pi is present in mitochondria as well as in the cytosol and nucleus in mammalian cell lines. A construct comprising the 84 amino acid residues in the amino-terminal region of GST pi and green fluorescent protein was detected in the mitochondria. The mutation of arginine to alanine at positions 12, 14, 19, 71, and 75 in full-length GST pi completely abrogated the ability to distribute in the mitochondria, suggesting that arginine, a positively charged residue, is required for the mitochondrial transport of GST pi. Chemicals generating reactive oxygen species, such as rotenone and antimycin A, decreased cell viability and reduced mitochondrial membrane potential. The overexpression of GST pi diminished these changes. GST pi-targeting siRNA abolished the protective effect of GST pi on the mitochondria under oxidative stress. The findings indicate that the peptide signal is conducive to the mitochondrial localization of GST pi under steady-state conditions without alternative splicing or posttranslational modifications such as proteolysis, suggesting that GST pi protects mitochondria against oxidative stress

Dehydroepiandrosterone augments sensitivity to gamma-ray irradiation in human H4 neuroglioma cells through down-regulation of Akt signaling.

Dehydroepiandrosterone (DHEA) modulates sensitivity to radiation-induced injury in human neuroglioma cells (H4) through effects on Akt signalling by glutathione (GSH)-dependent redox regulation. Previous treatment of H4 cells with DHEA for 18 h reduced the gamma-ray-induced phosphorylation of Akt, activated p21(waf1) synthesis and up-regulated phosphorylation of Rb independent of p53. These reactions were followed by a decrease in cell number and an increase in apoptosis and G(2)/M checkpoint arrest. The suppression of phosphorylation of Akt by DHEA was due to regulation of the dephosphorylation by protein phosphatase 2A (PP2A). DHEA up-regulated the expression of gamma-glutamylcysteine synthetase, a rate-limiting enzyme of glutathione (GSH) synthesis, and the levels of GSH to maintain PP2A activity. The results suggested that DHEA increases the sensitivity of cells to gamma-ray irradiation by inducing apoptosis and cell cycle arrest through GSH-dependent regulation of the reduced form of PP2A to down-regulate the Akt signalling pathway

The Histological Features of a Myocardial Biopsy Specimen in a Patient in the Acute Phase of Reversible Catecholamine-induced Cardiomyopathy due to Pheochromocytoma

A 63-year-old Japanese woman with an adrenal tumor was transferred to our hospital due to cardiogenic shock. Right and left ventriculography showed severe hypokinesis of the middle segment and the apex in both ventricles, and an endomyocardial biopsy demonstrated a small number of necrotic myocytes and cellular infiltration. She was diagnosed with pheochromocytoma and quickly recovered after treatment with an α-blocker. The functional disability of both the right and left ventricles with less myocardial damage due to an excessive level of catecholamine seemed to be related to the early recovery the present patient with catecholamine-induced cardiomyopathy due to pheochromocytoma

Corepressor for element-1–silencing transcription factor preferentially mediates gene networks underlying neural stem cell fate decisions

The repressor element-1 (RE1) silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF) silences neuronal genes in neural stem cells (NSCs) and nonneuronal cells through its role as a dynamic modular platform for recruitment of transcriptional and epigenetic regulatory cofactors to RE1-containing promoters. In embryonic stem cells, the REST regulatory network is highly integrated with the transcriptional circuitry governing self-renewal and pluripotency, although its exact functional role is unclear. The C-terminal cofactor for REST, CoREST, also acts as a modular scaffold, but its cell type-specific roles have not been elucidated. We used chromatin immunoprecipitation-on-chip to examine CoREST and REST binding sites in NSCs and their proximate progenitor species. In NSCs, we identified a larger number of CoREST (1,820) compared with REST (322) target genes. The majority of these CoREST targets do not contain known RE1 motifs. Notably, these CoREST target genes do play important roles in pluripotency networks, in modulating NSC identity and fate decisions and in epigenetic processes previously associated with both REST and CoREST. Moreover, we found that NSC-mediated developmental transitions were associated primarily with liberation of CoREST from promoters with transcriptional repression favored in less lineage-restricted radial glia and transcriptional activation favored in more lineage-restricted neuronal-oligodendrocyte precursors. Clonal NSC REST and CoREST gene manipulation paradigms further revealed that CoREST has largely independent and previously uncharacterized roles in promoting NSC multilineage potential and modulating early neural fate decisions