热激蛋白90抑制剂

分子伴侣热激蛋白90(heat-shock protein 90,Hsp90)在生物体内具有重要的生理功能,它在许多肿瘤细胞中表达增加。临床研究发现Hsp90抑制剂单一用药或者联合用药都具有较好的抗肿瘤效果,因此目前Hsp90被认为是癌症治疗一个非常有潜力的靶标。本文总结了Hsp90的结构功能、Hsp90抑制剂的作用机理以及Hsp90抑制剂的临床应用前景,希望为设计和开发新的Hsp90抑制剂提供一定的参考。     

热休克蛋白90在肝细胞癌中的研究进展

肝细胞癌中蛋白质稳态是其生长和转移的基础, Hsp90作为分子伴侣可维持多种促癌分子的稳定性,并抑制抑癌分子的活性,使蛋白质合成和降解之间保持平衡,致使癌细胞在恶劣微环境的持续刺激下依旧可以生存。然而, Hsp90抑制剂因在临床试验中表现出严重的不良反应,故迄今没有一种抑制剂获得FDA的批准。该篇文章阐述了Hsp90的结构、表达调控、伴侣循环以及Hsp90过表达与肝细胞癌之间的联系,旨在阐明Hsp90在肝细胞癌发生发展中的作用,为临床用药提供理论依据。     

Hsp90抑制剂对未折叠蛋白反应作用的研究进展

肿瘤细胞因癌基因突变、缺氧及营养受限而高度依赖未折叠蛋白反应(unfolded protein response,UPR)。细胞通过内质网(endoplasmic reticulum,ER)膜上3个跨膜蛋白感知未折叠蛋白信号,引起未折叠蛋白反应,动态调控内质网折叠能力,一方面通过暂时减缓翻译和加快蛋白质流出减少ER蛋白质折叠负担,另一方面通过转录因子提高伴侣分子合成,增加ER折叠能力。未折叠的蛋白质长时间积聚在ER会对细胞产生毒性,引起不能缓解的ER应激状态,启动细胞凋亡程序。热休克蛋白90(heat shock protein 90,Hsp90)是一种进化保守的伴侣分子,参与了300多种新生蛋白质的折叠与成熟,其中包括UPR重要信号IRE1α(inositol-requiring enzyme 1α)。Hsp90抑制剂导致细胞产生大量未折叠蛋白质,同时直接诱导IRE1α的降解,从而破坏UPR恢复蛋白质平衡的能力,诱导UPR相关凋亡。目前,Hsp90抑制剂可有效诱导分泌型肿瘤细胞如骨髓瘤以及RAS突变肿瘤UPR途径的凋亡。     

Hsp90分子抑制剂拮抗肿瘤耐药的研究进展

Hsp90作为热休克蛋白家族中的重要一员,是一种对细胞生存所必需的分子伴侣,它发挥着稳定顾客蛋白构象、维持其功能的作用。许多顾客蛋白在肿瘤中处于过度表达或持续激活状态,与肿瘤的发生发展有着密切的关系。因此,Hsp90在近年的研究中倍受关注,已经发展为抗肿瘤治疗的良好靶点,目前已经有多个Hsp90抑制剂进入临床实验。近年随着肿瘤分子生物学的研究,肿瘤分子靶向治疗已取得明显成果,针对多种癌症已获得了多个用于靶向治疗的单克隆抗体或小分子化学物质,如用于治疗某些HER2阳性乳腺癌的曲妥珠单抗、用于治疗NSCLC的吉非替尼等。然而随着这些药物的应用,肿瘤耐药性不可避免的产生。多方面研究表明Hsp90抑制剂会引起与耐药相关的多个分子的降解,提示其在拮抗耐药方面具有重要的意义。本文就Hsp90分子抑制剂在拮抗肿瘤耐药方面的研究进行综述。     

FS36作为新型人源Hsp90抑制剂的发现

热休克蛋白90(Hsp90)通过对几百种蛋白质底物(客户蛋白质)进行合理的折叠、成熟其构象并且激活,在肿瘤细胞的生长和繁殖中发挥重要作用．因此,Hsp90成为非常有吸引力、有前途的抗肿瘤药物靶点,并且超过20种抑制剂已经进入临床实验阶段．我们在这里设计并合成了一个小分子抑制剂：FS36．收集了Hsp90^N-FS36复合物晶体结构的X射线衍射实验数据．高分辨率X射线晶体结构表明,FS36在ATP结合位点上与Hsp90^N相互作用,并且FS36可能替代核苷酸与Hsp90^N结合．FS36和Hsp90^N的复合物晶体结构和相互作用为后期设计和优化新型抗肿瘤药物奠定基础．     

TPR蛋白对Hsp90功能的调节

热激蛋白Hsp90是一类在进化中形成的高度保守的且可参与多种细胞功能的特异分子伴侣。TPR蛋白通常存在于Hsp90的多蛋白质复合物中,它对Hsp90的功能的多样性起着至关重要的作用,同时Hsp90可能为TPR蛋白提供“泊位”,允许不同的TPR蛋白在Hsp90分子伴侣底物附近有序而特异结合,从而使Hsp90在细胞内环境中以特定的方式完成其各种细胞功能。了解TPR蛋白与Hsp90的相互作用机制为阐明细胞内Hsp90的功能多样性和特异性奠定了基础。     

Hsp90 inhibition results in autophagy-mediated proteasome-independent degradation of IκB kinase （IKK）

Autophagic and proteasomal proteolysis are two major pathways for degradation of cellular constituents. Current models suggest that autophagy is responsible for the nonselective bulk degradation of long-lived proteins and organelles while the proteasome specifically degrades short-lived proteins including misfolded proteins caused by the absence of Hsp90 function. Here, we show that the IκB kinase （IKK）, an essential activator of NF-κB, is selectively degraded by autophagy when Hsp90 is inhibited by geldanamycin （GA）, a specific Hsp90 inhibitor showing highly effective anti-tumor activity. We find that in this case inactivation of ubiquitination or proteasome fails to block IKK degradation. However, inhibition of autophagy by an autophagy inhibitor or knockout of Atg5, a key component of the autophagy pathway, significantly rescues IKK from GA-induced degradation. These findings provide the first evidence that an Hsp90 client may be degraded by a mechanism different from the proteasome pathway and establish a molecular link among Hsp90, NF-κB and autophagy     

Hsp90伴侣复合体装配及对类固醇受体调节

真核细胞中近100种蛋白质都受Hsp90的调节。这些蛋白质多与信号转导作用有关,它们与Hsp90一起进入一个以Hsp90/Hsp70为主的伴侣复合体,在复合体内完成信号转导作用。Hsp90除了和蛋白质的伴侣位点结合以外,还在其他位点与辅助因子连接,这是Hsp90能与蛋白质及辅助因子组装成复合体,并进而调节其信号作用的结构基础。类固醇受体等蛋白质的信号转导作用是在Hsp70、Hsp90为基础的5种蛋白质(Hsp90,Hsp70,Hop,Hsp40和p23)组成的复合体中进行的。这个系统可以帮助理解在真核细胞中,Hsp70和Hsp90怎样联合作用,改变底物蛋白构象,以及怎样应答信号作用。     

氧化应激对Hsp90α、ARF1 细胞内定位和相互作用的影响

目的:探讨氧化应激对热休克蛋白90α(Hsp90α)与ADP-核糖基化因子1(ARF1)细胞内定位、相互作用的影响。方法:应用500μM H2O2处理HepG2细胞,建立氧化应激模型,MTT比色法检测细胞活力,Western blotting检测Hsp90α和ARF1水平,细胞免疫荧光法、免疫共沉淀检测上述蛋白在氧化应激下的分布、共定位变化和相互作用。结果:MTT比色法结果提示,随氧化应激时间延长,细胞存活力降低;Western blotting结果显示,氧化应激可提高胞内Hsp90α和ARF1蛋白水平;免疫共沉淀结果显示,随氧化应激作用时间延长,Hsp90α与ARF1相互结合增多;细胞免疫荧光结果显示,随氧化应激作用时间延长,Hsp90α与ARF1荧光强度增强,并趋于沿胞膜分布。结论:提示氧化应激影响Hsp90α和ARF1的水平、胞内分布及相互作用。     

人Hsp90α基因克隆、中试发酵及生物信息学分析

目的:克隆获得人热休克蛋白90α(Hsp90α)基因,构建其原核表达载体,分离纯化重组蛋白,为Hsp90抑制剂的体外筛选奠定基础.方法:TRIzol Reagent法提取K562细胞总RNA,通过RT-PCR获得Hsp90α-cDNA.以该cDNA为模板PCR扩增Hsp90α基因,目的基因和质粒pET28a(+)经Nco Ⅰ和Xho Ⅰ双酶切后,连接酶切片段,将重组DNA转化DH5α,酶切及测序鉴定重组体.将构建好的重组质粒转化Rosetta(DE3)菌株,IPTG诱导,经条件优化后进行中试发酵、纯化以及Western blot鉴定.结果:原核表达载体pET28a(+)-Hsp90α成功构建,可在Rosetta(DE3)中正确表达,中试发酵收菌574g且表达产物以可溶性形式存在,纯化产物纯度为97%.结论:利用分子克隆技术建立了Hsp90α基因的原核表达和中试发酵的条件,为更深入地研究其在抗肿瘤治疗中的作用打下基础.     

植物热激蛋白90的结构和功能

文章从结构和功能两个方面介绍植物热激蛋白90的研究进展。     

热休克蛋白90 抑制剂的活性初步评价

目的:初步评价经计算机模拟筛选的Fs系列化合物对A549细胞的增殖抑制作用与对热休克蛋白90活性的抑制。方法:首先采用SRB(磺基罗丹明B)法观察26个化合物对A549肿瘤细胞增殖抑制活性,再进一步应用Western Blot方法对此类化合物在蛋白水平上对热休克蛋白90活性的抑制进行评价。以热休克蛋白70的表达增加作为热休克蛋白90活性是否被抑制的参考指标。结果:在Fs系列化合物中Fs-1、Fs-8、Fs-24对A549细胞增殖有明显抑制,且能明显上调Hsp70蛋白的表达,但同时Hsp90蛋白的表达量并不受影响。其余化合物在两种方法中显示均无明显抑制作用。结论:在经计算机模拟筛选出的26种Fs系列化合物中Fs-1、Fs-8、Fs-24可抑制A549细胞的增殖,可能是通过对Hsp90活性的抑制而发挥作用,经筛选其余Fs系列化合物抑制A549细胞增殖与抑制Hsp90活性作用均不显著。Fs-1、Fs-8、Fs-24类化合物作用的初步探索将为研制Hsp90靶向抑制剂类药物开辟新途径。     

The 90-kDa Heat Shock Protein Hsp90 Protects Tubulin against Thermal Denaturation

Hsp90 and tubulin are among the most abundant proteins in the cytosol of eukaryotic cells. Although Hsp90 plays key roles in maintaining its client proteins in their active state, tubulin is essential for fundamental processes such as cell morphogenesis and division. Several studies have suggested a possible connection between Hsp90 and the microtubule cytoskeleton. Because tubulin is a labile protein in its soluble form, we investigated whether Hsp90 protects it against thermal denaturation. Both proteins were purified from porcine brain, and their interaction was characterized in vitro by using spectrophotometry, sedimentation assays, video-enhanced differential interference contrast light microscopy, and native polyacrylamide gel electrophoresis. Our results show that Hsp90 protects tubulin against thermal denaturation and keeps it in a state compatible with microtubule polymerization. We demonstrate that Hsp90 cannot resolve tubulin aggregates but that it likely binds early unfolding intermediates, preventing their aggregation. Protection was maximal at a stoichiometry of two molecules of Hsp90 for one of tubulin. This protection does not require ATP binding and hydrolysis by Hsp90, but it is counteracted by geldanamycin, a specific inhibitor of Hsp90.     

Interaction of Heat Shock Protein 90 and the Co-chaperone Cpr6 with Ura2, a Bifunctional Enzyme Required for Pyrimidine Biosynthesis

The molecular chaperone heat shock protein 90 (Hsp90) is an essential protein required for the activity and stability of multiple proteins termed clients. Hsp90 cooperates with a set of co-chaperone proteins that modulate Hsp90 activity and/or target clients to Hsp90 for folding. Many of the Hsp90 co-chaperones, including Cpr6 and Cpr7, contain tetratricopeptide repeat (TPR) domains that bind a common acceptor site at the carboxyl terminus of Hsp90. We found that Cpr6 and Hsp90 interacted with Ura2, a protein critical for pyrimidine biosynthesis. Mutation or inhibition of Hsp90 resulted in decreased accumulation of Ura2, indicating it is an Hsp90 client. Cpr6 interacted with Ura2 in the absence of stable Cpr6-Hsp90 interaction, suggesting a direct interaction. However, loss of Cpr6 did not alter the Ura2-Hsp90 interaction or Ura2 accumulation. The TPR domain of Cpr6 was required for Ura2 interaction, but other TPR containing co-chaperones, including Cpr7, failed to interact with Ura2 or rescue CPR6-dependent growth defects. Further analysis suggests that the carboxyl-terminal 100 amino acids of Cpr6 and Cpr7 are critical for specifying their unique functions, providing new information about this important class of Hsp90 co-chaperones.     

热激蛋白90与热激应答

热激蛋白90(heat shock protein 90,HSP90)作为机体重要的分子伴侣之一,主要是维持机体内环境的稳态.在机体遭受内外界刺激时,体内氧化-抗氧化平衡失调诱发机体热激应答,诱导HSP90高表达来抵御刺激对机体造成的损伤.     

A Novel C-Terminal Homologue of Aha1 Co-Chaperone Binds to Heat Shock Protein 90 and Stimulates Its ATPase Activity in Entamoeba histolytica

Cytosolic heat shock protein 90 (Hsp90) has been shown to be essential for many infectious pathogens and is considered a potential target for drug development. In this study, we have carried out biochemical characterization of Hsp90 from a poorly studied protozoan parasite of clinical importance, Entamoeba histolytica. We have shown that Entamoeba Hsp90 can bind to both ATP and its pharmacological inhibitor, 17-AAG (17-allylamino-17-demethoxygeldanamycin), with K_d values of 365.2 and 10.77 μM, respectively, and it has a weak ATPase activity with a catalytic efficiency of 4.12 × 10^− 4 min^− 1 μM^− 1. Using inhibitor 17-AAG, we have shown dependence of Entamoeba on Hsp90 for its growth and survival. Hsp90 function is regulated by various co-chaperones. Previous studies suggest a lack of several important co-chaperones in E. histolytica. In this study, we describe the presence of a novel homologue of co-chaperone Aha1 (activator of Hsp90 ATPase), EhAha1c, lacking a canonical Aha1 N-terminal domain. We also show that EhAha1c is capable of binding and stimulating ATPase activity of EhHsp90. In addition to highlighting the potential of Hsp90 inhibitors as drugs against amoebiasis, our study highlights the importance of E. histolytica in understanding the evolution of Hsp90 and its co-chaperone repertoire.