Department of Chemical Sciences and Technologies, University of Tor Vergata, Rome, Italy.
Biochemistry. 2012 Sep 18;51(37):7304-12. doi: 10.1021/bi300559m. Epub 2012 Sep 5.
The role played by glutathione transferase P1-1 (GSTP1-1) in modulating the c-Jun N-terminal kinase (JNK) pathway has been extensively investigated using JNK isoforms known to exert opposite effects in the cells. We have expressed isoform JNK1α2, which has been reported to transmit a pro-apoptotic signal, and we have analyzed both the phosphorylation level and the activity of this kinase in the presence of GSTP1-1. Contrary to what previous studies suggest, we found that GSTP1-1 is able to form a complex with the unphosphorylated and inactive JNK1α2 isoform, even in the absence of the substrate. We also analyzed the consequences of this interaction on the activity of both enzymes. The complex strongly reduced the extent of activation of JNK1α2 and preserved GSTP1-1 from inactivation. Unexpectedly, glutathione (GSH) exerted a negative effect on the affinity of GSTP1-1 for JNK1α2, suggesting that the intracellular levels of this thiol may allow a fine-tuning of the MAPK signaling pathway. Moreover, we found that the adduct formed by GSH and the strong GSTP1-1 inhibitor NBDHEX abolishes the interaction between GSTP1-1 and JNK1α2. These data confirm and extend at the molecular level previous evidence obtained in tumor cell lines.
谷胱甘肽 S-转移酶 P1-1（GSTP1-1）在调节 c-Jun N-末端激酶（JNK）途径中的作用已通过已知在细胞中产生相反作用的 JNK 同工型进行了广泛研究。我们表达了 JNK1α2 同工型，据报道该同工型传递促凋亡信号，并且我们分析了 GSTP1-1 存在时该激酶的磷酸化水平和活性。与先前的研究表明相反，我们发现 GSTP1-1 能够与未磷酸化和无活性的 JNK1α2 同工型形成复合物，即使在没有底物的情况下也是如此。我们还分析了这种相互作用对两种酶活性的影响。该复合物强烈降低了 JNK1α2 的激活程度，并使 GSTP1-1 免于失活。出乎意料的是，谷胱甘肽（GSH）对 GSTP1-1 与 JNK1α2 的亲和力产生了负面影响，这表明这种硫醇的细胞内水平可能允许对 MAPK 信号通路进行微调。此外，我们发现 GSH 和强 GSTP1-1 抑制剂 NBDHEX 形成的加合物会破坏 GSTP1-1 与 JNK1α2 之间的相互作用。这些数据在分子水平上证实并扩展了先前在肿瘤细胞系中获得的证据。
