Analysis of the signal transduction pathway of the transcription factor NF-κB activated by cytokines

乙酰氧放线菌酮（E-73）抑制肿瘤坏死因子对肺癌A549细胞核转录因子NF-κB的诱导。虽然E-73不能影响衔接蛋白TRADD、RIP和TRAF 2的表达，这些蛋白对于NF-κB信号通路的激活是必需的，但该试剂通过激活p38 MAP激酶诱导细胞表面TNF受体1的下调。相比之下，E-73选择性地诱导人白血病HL-60和Jurkat T细胞中线粒体的半胱天冬酶依赖性凋亡和细胞色素c释放。E-73诱导的细胞色素c释放被Bcl-2家族成员Bcl-x_L和JNK抑制剂SP 600125阻断，但不受半胱天冬酶抑制剂z-VAD-favor和p38 MAP激酶抑制剂SB 203580的影响。因此，这些数据表明，E-73诱导细胞色素c从线粒体释放通过JNK激活，从而触发caspase cascades.The真菌毒素青霉酸抑制细胞凋亡，通过阻止激活caspase-8，但不招募caspase-8进入Fas-FADD复合物后，刺激Fas配体（FasL）。青霉素酸抑制caspase-3、caspase-8和酪蛋白酶-9的酶活性。然而，青霉酸弱抑制半胱天冬酶-3和酪蛋白酶-9在星形孢菌素处理的细胞中的活化，但抑制半胱天冬酶-8在FasL处理的细胞中的活化，表明青霉酸在细胞水平上选择性地靶向半胱天冬酶-8。谷氨酸和半胱氨酸抑制了青霉酸对caspase-8的抑制作用，青霉酸直接与caspase-8的活性中心半胱氨酸结合。这些结果表明，青霉酸抑制FasL诱导的细胞凋亡，通过阻断caspase-8的自我加工。

Acetoxycycloheximide (E-73) inhibits induction of the transcription factor NF-κB by TNF in the lung carcinoma A549 cells. Although E-73 failed to affect the expression of the adaptor proteins TRADD, RIP, and TRAF2, which are essential for activation of the NF-κB signaling pathway, the agent induced the downregulation of the cell-surface TNF receptor 1 via activation of p38 MAP kinase. By contrast, E-73 selectively induced caspase-dependent apoptosis and cytochrome c release from mitochondria in the human leukemia HL-60 and Jurkat T cells. E-73-induced cytochrome c release was blocked by the Bcl-2 family member Bcl-x_L and the JNK inhibitor SP600125, but was unaffected by the caspase inhibitor z-VAD-fmk and the p38 MAP kinase inhibitor SB203580. Thus, these data suggest that E-73 induces cytochrome c release from mitochondria through the JNK activation, thereby triggering the caspase cascade.The mycotoxin penicillic acid inhibited apoptosis by preventing activation of caspase-8, but not recruitment of caspase-8 into the Fas-FADD complex upon stimulation with Fas ligand (FasL). Penicillic acid inhibited the enzymatic activities of caspase-3, caspase-8, and casoase-9. However, penicillic acid weakly inhibited activation of caspase-3 and casoase-9 in staurosporine-treated cells, but did inhibit caspase-8 activation in FasL-treated cells, suggesting that penicillic acid selectively targets caspase-8 at the cellular level. Glutathione and cysteine suppressed the inhibitory effect of penicillic acid on caspase-8, and penicillic acid directly bound to the active center cysteine of caspase-8. These results demonstrate that penicillic acid inhibits FasL-induced apoptosis by blocking the self-processing of caspase-8.