Metabolic Oxidative Stress-induced HSP70 Gene Expression Is Mediated through SAPK Pathway

Abstract

In previous reports we demonstrated that glucose deprivation induces metabolic oxidative stress in drugresistant human breast carcinoma MCF-7/ADR cells (Lee, Y. J., Galoforo, S. S., Berns, c. M., Chen, J. C., Davis, B. H., Swim, J. E., Corry, P. M., and Spitz, D. R. (1998) J. Biol. Chem. 273, 5294 -5299). In the study described here, we investigated intracellular responses to metabolic oxidative stress. Northern blots show an increase in the level of HSP70 and HSP28 mRNA in cells exposed to glucose-free medium for 1 h. One-and two-dimensional polyacrylamide gel analyses confirmed that glucose deprivation induced a family of HSPs, particularly an inducible HSP70. Overexpression of bcl-2 suppressed glucose deprivation-induced HSP70 gene expression, heat shock transcription factor-heat shock element binding activity, as well as c-Jun NH 2 -terminal kinase (JNK1) activation. Expression of a dominant-negative mutant of JNK1 also suppressed glucose deprivationinduced JNK1 activation as well as HSP70 gene expression. Taken together, the stress-activated protein kinase signal transduction pathway is involved in glucose deprivation-induced heat shock gene expression.It is well established that the transcriptional induction of heat shock genes in eukaryotes is mediated by the heat shock transcription factor (HSF) 1 (1-8). This protein can be activated by a variety of stresses such as heat shock, heavy metals, or arsenite (4, 9 -11). The activated HSF binds to the promoters which contain the heat shock element (HSE) and then stimulates transcription (1,5,12). A fundamental question which remains unanswered is how these stresses activate HSF. HSF is phosphorylated under normal growth conditions and is hyperphosphorylated subsequent to stress. It has been proposed that such phosphorylation may be mediated through the MAP kinase family such as c-Jun NH 2 -terminal kinase (JNK) (13).Several reports have demonstrated that the JNK, also referred to as stress-activated protein kinase (SAPK), signal transduction pathway can be activated by oxidative stress (14 -16). Following activation, JNK phosphorylates several transcription factors including activating transcription factor-2 (17), Elk-1 (18), , and c-Jun (20) which are involved in regulating numerous genes implicated in cell proliferation, transformation, differentiation, and DNA repair (21-24). Recent studies also show that oxidative stress can activate HSF and increase HSP70 gene expression (25). These observations suggest a possibility that oxidative stress-induced activation of HSF is mediated through the SAPK pathway.We have previously observed that glucose deprivation increases intracellular hydroperoxide production and oxidized glutathione in drug-resistant human breast carcinoma MCF-7/ ADR cells (26). These results led us to investigate the possibility that glucose deprivation-induced metabolic oxidative stress may activate HSF through the SAPK pathway and result in hsp gene expression. In this study, we demonstrate that glucose deprivation induces HSP genes, in partic...

Nicotinamide Mononucleotide Adenylyltransferase Is a Stress Response Protein Regulated by the Heat Shock Factor/Hypoxia-inducible Factor 1α Pathway

“…Collectively, these results show that NMNAT was up-regulated under heat stress, hypoxia, or oxidative stress in a time-or dose-dependent manner similar to the stress protein Hsp70 (Fig. 1) as reported previously (6,30,31), suggesting that NMNAT may be transcriptionally up-regulated under a variety of stress conditions.…”

Microtubule Dysfunction Induced by Paclitaxel Initiates Apoptosis through Both c-Jun N-terminal Kinase (JNK)-dependent and -Independent Pathways in Ovarian Cancer Cells

“…Some reports suggest that Bcl-2 may act upstream of JNK/ SAPK (72,73). In BR cells, however, JNK/SAPK activation peaked at 2 h (14), while Bcl-2 phosphorylation and the G 2 /M arrest of the cell cycle required 12-16 h of paclitaxel treatment.…”

Rac1 Regulates Stress-induced, Redox-dependent Heat Shock Factor Activation

“…JNKs are one of the many downstream targets of the rho family of small GTP-binding proteins (30). It has recently been shown that JNKs can mediate the transcriptional activation and posttranslational modification of certain heat shock proteins (31). We therefore investigated the possibility that regulation of stress-induced HSF activity by Rac1 was mediated via the activation of JNKs.…”

“…Extracellular stresses also lead to phosphorylation of HSFs (39), and therefore redox-modulated changes in protein phosphorylation may contribute to HSF-1 activation. In this regard, several studies have implicated JNK-regulated phosphorylation of HSFs in augmenting the heat shock response to specific stresses (31,40). Our observation that SEK(KR) abrogates the hypoxia/reoxygenation-induced HSF activation is in concert with these previous reports.…”