Identification of Mixed Lineage Leukemia 1(MLL1) Protein as a Coactivator of Heat Shock Factor 1(HSF1) Protein in Response to Heat Shock Protein 90 (HSP90) Inhibition

Heat shock protein 90 (HSP90) inhibition inhibits cancer cell proliferation through depleting client oncoproteins and shutting down multiple oncogenic pathways. Therefore, it is an attractive strategy for targeting human cancers. Several HSP90 inhibitors, including AUY922 and STA9090, show promising effects in clinical trials. However, the efficacy of HSP90 inhibitors may be limited by heat shock factor 1 (HSF1)-mediated feedback mechanisms. Here, we identify, through an siRNA screen, that the histone H3 lysine 4 methyltransferase MLL1 functions as a coactivator of HSF1 in response to HSP90 inhibition. MLL1 is recruited to the promoters of HSF1 target genes and regulates their expression in response to HSP90 inhibition. In addition, a striking combination effect is observed when MLL1 depletion is combined with HSP90 inhibition in various human cancer cell lines and tumor models. Thus, targeting MLL1 may block a HSF1-mediated feedback mechanism induced by HSP90 inhibition and provide a new avenue to enhance HSP90 inhibitor activity in human cancers.     

正显性热休克因子1突变体抑制6-OHDA诱导细胞死亡的研究

热休克因子1是真核细胞应激反应时热休克蛋白表达的主要转录调控因子。它在非应激条件下被抑制性复合体抑制以非活化形式存在,只有在受到应激时才会暂时活化。通过基因突变得到的正显性突变体在不需要外界环境刺激的条件下就能激活细胞内源性热休克蛋白的表达。环境神经毒素是引起帕金森病的一个重要因素,它们能够氧化损伤多巴胺能神经元,最终引起细胞死亡。Western blot和双荧光素酶检测证明,在SH-SY5Y细胞中转染正显性热休克因子1突变体能够明显上调HSP70的表达。并且通过检测细胞培养基中的乳酸脱氢酶的含量证明正显性热休克因子1突变体能够显著抑制神经毒素6-羟基多巴胺诱导的细胞死亡。这些结果表明,正显性热休克因子1突变体在帕金森病的防治方面可能具有潜在的应用前景。     

热休克转录因子1与机体耐热性的相关研究

热休克转录因子1(HSF1)能够启动各种热休克蛋白基因的诱导表达,这对防止机体免受热应激损伤具有重要的意义。从HSF1的结构、功能及活化过程等几个方面阐述了HSF1的生理特征及其与机体耐热性能之间的关系。     

Muscle-specific MicroRNA1 (miR1) Targets Heat Shock Protein 70 (HSP70) during Dexamethasone-mediated Atrophy

High doses of dexamethasone (Dex) or myostatin (Mstn) induce severe atrophy of skeletal muscle. Here we show a novel microRNA1 (miR1)-mediated mechanism through which Dex promotes skeletal muscle atrophy. Using both C2C12 myotubes and mouse models of Dex-induced atrophy we show that Dex induces miR1 expression through glucocorticoid receptor (GR). We further show that Mstn treatment facilitates GR nuclear translocation and thereby induces miR1 expression. Inhibition of miR1 in C2C12 myotubes attenuated the Dex-induced increase in atrophy-related proteins confirming a role for miR1 in atrophy. Analysis of miR1 targets revealed that HSP70 is regulated by miR1 during atrophy. Our results demonstrate that increased miR1 during atrophy reduced HSP70 levels, which resulted in decreased phosphorylation of AKT, as HSP70 binds to and protects phosphorylation of AKT. We further show that loss of pAKT leads to decreased phosphorylation, and thus, enhanced activation of FOXO3, up-regulation of MuRF1 and Atrogin-1, and progression of skeletal muscle atrophy. Based on these results, we propose a model whereby Dex- and Mstn-mediated atrophic signals are integrated through miR1, which then either directly or indirectly, inhibits the proteins involved in providing protection against atrophy.     

Heat Shock Factor 1 Inducers from the Bark of Eucommia ulmoides as Cytoprotective Agents

The barks of Eucommia ulmoides (Eucommiae Cortex, Eucommiaceae) have been used as a traditional medicine in Korea, Japan, and China to treat hypertension, reinforce the muscles and bones, and recover the damaged liver and kidney functions. Among these traditional uses, to establish the recovery effects on the damaged organs on the basis of phytochemistry, the barks of E. ulmoides have been investigated to afford three known phenolic compounds, coniferaldehyde glucoside ( 1 ), bartsioside ( 2 ), and feretoside ( 3 ), which were found in the family Eucommiaceae for the first time. The compounds 1 – 3 were evaluated for their inducible activities on the heat shock factor 1 (HSF1), and heat shock proteins (HSPs) 27 and 70, along with four compounds, geniposide ( 4 ), geniposidic acid ( 5 ), pinoresinol diglucoside ( 6 ), and liriodendrin ( 7 ), which were previously reported from E. ulmoides. Compounds 1 – 7 increased expression of HSF1 by a factor of 1.214, 1.144, 1.153, 1.114, 1.159, 1.041, and 1.167 at 3 μM , respectively. Coniferaldehyde glucoside ( 1 ) showed the most effective increase of HSF1 and induced successive expressions of HSP27 and HSP70 in a dose‐dependent manner without cellular cytotoxicity, suggesting a possible application as a HSP inducer to act as cytoprotective agent.     

HSF1在子宫内膜癌细胞中的表达及其与抗氧化的相关性研究

目的:探讨子宫内膜癌细胞在受到过氧化氢刺激时热休克因子1(Heat Shock Factor 1,HSF1)表达的变化,以及HSF1对肿瘤细胞抗凋亡能力的影响。方法:选择子宫内膜癌的Ishikawa、HEC-1-B及RL95-2三株细胞。分别测定细胞中HSF1基因转录以及翻译表达水平。给予细胞不同浓度的H2O2刺激后,检测细胞内HSF1的mRNA表达变化并且统计受刺激后细胞受抑制情况,观察细胞存活和生长与HSF1含量的关系。结果:三株细胞中HSF1mRNA和蛋白表达的基水平不同;在受到H2O2刺激后,细胞内HSF1表达有不同程度的升高;Ishikawa、HEC-1-B细胞分别在受到较高浓度的H2O2刺激后,细胞存活率出现明显下降;而RL95-2细胞在受到相对低浓度的H2O2刺激后,细胞存活率即出现明显降低。结论:一定范围内浓度的H2O2刺激能够上调子宫内膜癌细胞中HSF1在转录以及蛋白水平的表达,而过高的浓度会使细胞中HSF1表达减少,对于不同细胞来说H2O2刺激的适宜浓度不同。而能使细胞增殖与增长发生明显变化的H2O2浓度与细胞内HSF1表达水平相关。     

Heat Shock Protein 83 (Hsp83) Facilitates Methoprene-tolerant (Met) Nuclear Import to Modulate Juvenile Hormone Signaling

Juvenile hormone (JH) receptors, methoprene-tolerant (Met) and Germ-cell expressed (Gce), transduce JH signals to induce Kr-h1 expression in Drosophila. Dual luciferase assay identified a 120-bp JH response region (JHRR) in the Kr-h1α promoter. Both in vitro and in vivo experiments revealed that Met and Gce transduce JH signals to induce Kr-h1 expression through the JHRR. DNA affinity purification identified chaperone protein Hsp83 as one of the proteins bound to the JHRR in the presence of JH. Interestingly, Hsp83 physically interacts with PAS-B and basic helix-loop-helix domains of Met, and JH induces Met-Hsp83 interaction. As determined by immunohistochemistry, Met is mainly distributed in the cytoplasm of fat body cells of the larval when the JH titer is low and JH induces Met nuclear import. Hsp83 was accumulated in the cytoplasm area adjunct to the nucleus in the presence of JH and Met/Gce. Loss-of-function of Hsp83 attenuated JH binding and JH-induced nuclear import of Met, resulting in a decrease in the JHRR-driven reporter activity leading to reduction of Kr-h1 expression. These data show that Hsp83 facilitates the JH-induced nuclear import of Met that induces Kr-h1 expression through the JHRR.