Down-regulation of the c-Jun N-terminal kinase (JNK) phosphatase M3/6 and activation of JNK by hydrogen peroxide and pyrrolidine dithiocarbamate

Abstract

Oxidative stress activates the c-Jun N-terminal kinase (JNK) pathway. However, the exact mechanisms by which reactive oxygen species (ROS) activate JNK are unclear. We found that the ability of hydrogen peroxide (H 2 O 2 ) to induce JNK activation varied in di erent cell types. Pyrrolidine dithiocarbamate (PDTC), a presumed antioxidant, induced JNK activation on its own and enhanced JNK activation by H 2 O 2 in many cell types, including Jurkat, HEK293, and LNCaP and Tsu-Pr1 prostate cancer cells. The activation of JNK by PDTC, in the presence or absence of exogenous H 2 O 2 , was dependent on its chelating ability to metal ions, most likely copper ions. Despite the strong JNK-activating ability, H 2 O 2 plus PDTC did not induce signi®cant activation of the upstream kinases, SEK1/MKK4 and MKK7. However, the JNK inactivation rate was slower in cells treated with H 2 O 2 plus PDTC compared with the rate in cells treated with ultraviolet C (UV-C). Treatment of H 2 O 2 plus PDTC signi®cantly decreased the expression levels of a JNK phosphatase, M3/6 (also named hVH-5), but not the levels of other phosphatases (PP2A and PP4). In contrast, UV-C irradiation did not cause the down-regulation of M3/6. These results suggest that JNK activation by H 2 O 2 plus PDTC resulted from the down-regulation of JNK phosphatases. Our data also reveal a necessity to carefully evaluate the pharmacological and biochemical properties of PDTC. Oncogene (2001) 20, 367 ± 374.

Overexpression of ErbB2 enhances ethanol-stimulated intracellular signaling and invasion of human mammary epithelial and breast cancer cells in vitro

“…We demonstrate here that ethanol differentially regulates ROS formation in the cells overexpressing ErbB2 and the cells with normal ErbB2 levels; cells with high levels of ErbB2 expression are more susceptible to ethanol-induced ROS formation. ROS may act as second messengers and activate intracellular signal cascade, including JNKs and p38 MAPK (Lo et al, 1996;Mansat-de Mas et al, 1999;Sano et al, 2001;Chen et al, 2001;Kulisz et al, 2002). However, our study indicates that catalase (a H 2 O 2 scavenger) does not affect either the activation of JNK/p38 MAPK or the cell invasion induced by ethanol.…”

Cellular response to oxidative stress: Signaling for suicide and survival*

“…Biochemical evidence indicates that under non-stressed conditions glutathione S-transferase (GST) binds to JNK and inhibits its activation, but that this interaction is disrupted by oxidative stress (Adler et al, 1999b). Several studies have provided evidence that JNK activation by hydrogen peroxide and/or stresses that affect the cellular redox state occurs in part through suppression of phosphatases involved in JNK inactivation (Meriin et al, 1999;Gabai et al, 2000a;Chen et al, 2001a). Thus, ROS might act at multiple levels in the JNK signaling pathway to regulate its activities.…”

ROS, stress‐activated kinases and stress signaling in cancer

“…A similar redox 'switch' has been documented for JNK, with ROS triggering the detachment of JNK associated glutathione-S-transferase-π (GSTp) and thereby facilitating JNK activation (Adler et al, 1999). ROS-dependent activation of JNK may also involve downregulation of a JNK phosphatase (Chen et al, 2001b), and additional, as yet unknown, mechanisms linking ROS and SAPKs undoubtedly exist. For instance, scaffold proteins have been gaining increasing interest as a mechanism for SAPK regulation (Davis, 2000), and the possibility that ROS-induced SAPK activation involves modulation of protein scaffolds merits investigation.…”