Hsu Li-Jin, Hong Qunying, Schultz Lori, Kuo Emory, Lin Sing-Ru, Lee Ming-Hui, Lin Yee-Shin, Chang Nan-Shan
Department of Immunology and Microbiology, National Cheng Kung University Medical College, 1 University Road, Tainan, 701 Taiwan, ROC.
Cell Signal. 2008 Jul;20(7):1303-12. doi: 10.1016/j.cellsig.2008.02.018. Epub 2008 Mar 4.
Zfra is a small size 31-amino-acid C2H2 zinc finger-like protein, which is known to interact with c-Jun N-terminal kinase 1 (JNK1), WW domain-containing oxidoreductase (WWOX, FOR or WOX1), TNF receptor-associated death domain protein (TRADD) and nuclear factor kappaB (NF-kappaB) during stress response. Here, we show that Zfra became phosphorylated at Ser8 (as determined by specific antibody) and translocated to the mitochondria in response to inducers of mitochondrial permeability transition (MPT) (e.g. staurosporine and betulinic acid). Overexpressed Zfra induced cell death. This event is associated, in part, with increased dissipation of mitochondrial membrane potential (MMP) and increased chromosomal DNA fragmentation. Intriguingly, Zfra significantly downregulated Bcl-2 and yet blocked cytochrome c release from the mitochondria. Overexpression of an S8G-Zfra mutant (Ser8 to Gly8 alteration) could not induce cell death, probably due to its failure of translocating to the mitochondria and causing MMP dissipation. Over-expressed proapoptotic WOX1 induced cytochrome c release from the mitochondria. Zfra bound and blocked the effect of WOX1. Taken together, Ser8 is essential for overexpressed Zfra to exert cell death via the mitochondrial pathway. Zfra downregulates Bcl-2 and induces MMP dissipation but causes no cytochrome c release, indicating a novel death pathway from the mitochondria.
Zfra是一种由31个氨基酸组成的小尺寸C2H2锌指样蛋白，已知在应激反应过程中它可与c-Jun氨基末端激酶1（JNK1）、含WW结构域的氧化还原酶（WWOX，FOR或WOX1）、肿瘤坏死因子受体相关死亡结构域蛋白（TRADD）以及核因子κB（NF-κB）相互作用。在此，我们发现Zfra在Ser8位点发生磷酸化（通过特异性抗体检测确定），并响应线粒体通透性转换（MPT）诱导剂（如星形孢菌素和桦木酸）转位至线粒体。过表达的Zfra诱导细胞死亡。这一事件部分与线粒体膜电位（MMP）耗散增加和染色体DNA片段化增加有关。有趣的是，Zfra显著下调Bcl-2，但阻止细胞色素c从线粒体释放。S8G-Zfra突变体（Ser8突变为Gly8）的过表达不能诱导细胞死亡，可能是由于其无法转位至线粒体并导致MMP耗散。过表达的促凋亡WOX1诱导细胞色素c从线粒体释放。Zfra结合并阻断了WOX1的作用。综上所述，Ser8对于过表达的Zfra通过线粒体途径发挥细胞死亡作用至关重要。Zfra下调Bcl-2并诱导MMP耗散，但不导致细胞色素c释放，表明存在一种来自线粒体的新死亡途径。
