吐温80合并温热诱导BGC-823胃癌细胞凋亡及对Hsp70,Bcl-2和Bax表达的影响

目的　观察膜活化剂吐温 80合并温热作用对BGC 82 3人胃癌细胞生长、凋亡及对Hsp70、Bcl 2、Bax表达的影响。方法　应用MTT法、荧光染色及DNA琼脂糖凝胶电泳 ,测定 0 1%吐温 80与 4 2℃ 10 0min合并作用对BGC 82 3细胞的抑制效应和诱导细胞凋亡的影响 ;应用免疫细胞化学染色 ,观察合并作用后不同时间 (0h、 8h、 16h、 2 4h)BGC 82 3细胞Hsp70、Bcl 2、Bax的表达改变。结果　①吐温 80合并 4 2℃温热作用对细胞具有明显的抑制效应 (P <0 0 0 1)。②合并作用后 2 4h ,可见大量肿瘤细胞凋亡。③合并作用可明显抑制BGC 82 3细胞Hsp70的表达 ;Bcl 2、Bax的表达均增加 ,且Bax的表达强于Bcl 2 ,并全部分布在胞浆。结论　吐温 80合并 4 2℃温热可通过诱导细胞凋亡来抑制肿瘤细胞生长 ,其对细胞Hsp70表达的抑制和对Bcl 2、Bax表达及分布的影响可能与凋亡的发生有关     

Moderate- and high-intensity exhaustive exercise in the heat induce a similar increase in monocyte Hsp72

This study examined the relationship between exhaustive exercise in the heat at moderate and high intensities on the intracellular heat shock protein 72 (iHsp72) response. Twelve male subjects cycled to exhaustion at 60 and 75 % of maximal oxygen uptake in hot conditions (40 °C, 50 % RH). iHsp72 concentration was measured in monocytes before, at exhaustion and 24 h after exercise. Rectal temperature, heart rate and oxygen uptake were recorded during exercise. Volitional exhaustion occurred at 58.9 ± 12.1 and 27.3 ± 9.5 min (P < 0.001) and a rectal temperature of 39.8 ± 0.4 and 39.2 ± 0.6 °C (P = 0.002), respectively, for 60 and 75 %. The area under the curve above a rectal temperature of 38.5 °C was greater at 60 % (17.5 ± 6.6 °C min) than 75 % (3.4 ± 4.8 °C min; P < 0.001), whereas the rate of increase in rectal temperature was greater at 75 % (5.1 ± 1.7 vs. 2.2 ± 1.4 °C h⁻¹; P < 0.001). iHsp72 concentration increased similarly at exhaustion relative to pre-exercise (P = 0.044) and then increased further at 24 h (P < 0.001). Multiple regression analysis revealed no predictor variables associated with iHsp72 expression; however, a correlation was observed between exercise intensities for the increase in iHsp expression at exhaustion and 24 h (P < 0.05). These results suggest that iHsp72 expression increased in relation to the level of hyperthermia attained and sustained at 60 % and the higher metabolic rate and greater rate of increase in core temperature at 75 %, with the further increase in iHsp72 concentration 24 h after exercise reinforcing its role as a chaperone and cytoprotective agent.     

Heat Shock RNA Levels in Brain and Other Tissues After Hyperthermia and Transient Ischemia

A number of studies have demonstrated increased synthesis of heat shock proteins in brain following hyperthermia or transient ischemia. In the present experiments we have characterized the time course of heat shock RNA induction in gerbil brain after ischemia, and in several mouse tissues after hyperthermia, using probes for RNAs of the 70-kilodalton heat shock protein (hsp70) family, as well as ubiquitin. A synthetic oligonucleotide selective for inducible hsp70 sequences proved to be the most sensitive indicator of the stress response whereas a related rat cDNA detected both induced RNAs and constitutively expressed sequences that were not strongly inducible in brain. Considerable polymorphism of ubiquitin sequences was evident in the outbred mouse and gerbil strains used in these studies when probed with a chicken ubiquitin cDNA. Brief hyperthermic exposure resulted in striking induction of hsp70 and several-fold increases in ubiquitin RNAs in mouse liver and kidney peaking 3 h after return to room temperature. The oligonucleotide selective for hsp70 showed equivalent induction in brain that was more rapid and transient than observed in liver, whereas minimal induction was seen with the ubiquitin and hsp70-related cDNA probes. Transient ischemia resulted in 5- to 10-fold increases in hsp70 sequences in gerbil brain which peaked at 6 h recirculation and remained above control levels at 24 h, whereas a modest 70% increase in ubiquitin sequences was noted at 6 h. These results demonstrate significant temporal and quantitative differences in heat shock RNA expression between brain and other tissues following hyperthermia in vivo, and indicate that hsp70 provides a more sensitive index of the stress response in brain than does ubiquitin after both hyperthermia and ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bax-inhibiting peptide derived from mouse and rat Ku70

Bax is a proapoptotic protein that plays a key role in the induction of apoptosis. Ku70 has activities to repair DNA damage in the nucleus and to suppress apoptosis by inhibiting Bax in the cytosol. We previously designed peptides based on the amino acid sequence of Bax-binding domain of human Ku70, and showed that these peptides bind Bax and inhibit cell death in human cell lines. In the present report, we examined the biological activities of other pentapeptides, VPTLK and VPALR, derived from mouse and rat Ku70. Cells in culture accumulated FITC-labeled VPTLK and VPALR, indicating that these peptides are cell permeable (human, mouse, rat, and porcine cells were examined). These peptides bound to Bax and suppressed cell death in various cell types including primary cultured cells. These data suggest that such Bax inhibiting peptides from three mammalian species may be used to protect healthy cells from apoptotic injury under pathological conditions.     

Multiphoton ANS fluorescence microscopy as an in vivo sensor for protein misfolding stress

The inability of cells to maintain protein folding homeostasis is implicated in the development of neurodegenerative diseases, malignant transformation, and aging. We find that multiphoton fluorescence imaging of 1-anilinonaphthalene-8-sulfonate (ANS) can be used to assess cellular responses to protein misfolding stresses. ANS is relatively nontoxic and enters live cells and cells or tissues fixed in formalin. In an animal model of Alzheimer’s disease, ANS fluorescence imaging of brain tissue sections reveals the binding of ANS to fibrillar deposits of amyloid peptide (Aβ) in amyloid plaques and in cerebrovascular amyloid. ANS imaging also highlights non-amyloid deposits of glial fibrillary acidic protein in brain tumors. Cultured cells under normal growth conditions possess a number of ANS-binding structures. High levels of ANS fluorescence are associated with the endoplasmic reticulum (ER), Golgi, and lysosomes—regions of protein folding and degradation. Nuclei are virtually devoid of ANS binding sites. Additional ANS binding is triggered by hyperthermia, thermal lesioning, proteasome inhibition, and induction of ER stress. We also use multiphoton imaging of ANS binding to follow the in vivo recovery of cells from protein-damaging insults over time. We find that ANS fluorescence tracks with the binding of the molecular chaperone Hsp70 in compartments where Hsp70 is present. ANS highlights the sensitivity of specific cellular targets, including the nucleus and particularly the nucleolus, to thermal stress and proteasome inhibition. Multiphoton imaging of ANS binding should be a useful probe for monitoring protein misfolding stress in cells.     

Distinguishing integral and receptor-bound heat shock protein 70 (Hsp70) on the cell surface by Hsp70-specific antibodies

Cell Stress & Chaperones journal has become a major outlet for papers and review articles about anti-heat shock protein (HSP) antibodies. In the last decade, it became evident that apart from their intracellular localization, members of the heat shock protein 90 (Hsp90; HSPC) and Hsp70 (HSPA) family are also found on the cell surface. In this review, we will focus on Hsp70 (HSPA1A), the major stress-inducible member of the human Hsp70 family. Depending on the cell type, the membrane association of Hsp70 comes in two forms. In tumor cells, Hsp70 appears to be integrated within the plasma membrane, whereas in non-malignantly transformed (herein termed normal) cells, Hsp70 is associated with cell surface receptors. This observation raises the question whether or not these two surface forms of Hsp70 in tumor and normal cells can be distinguished using Hsp70 specific antibodies. Presently a number of Hsp70 specific antibodies are commercially available. These antibodies were generated by immunizing mice either with recombinant or HeLa-derived human Hsp70 protein, parts of the Hsp70 protein, or with synthetic peptides. This review aims to characterize the binding of different anti-human Hsp70 antibodies and their capacity to distinguish between integrated and receptor-bound Hsp70 in tumor and normal cells.     

The discovery of Hsp70 domain with cell-penetrating activity

Chaperone Hsp70 can cross the plasma membrane of living cells using mechanisms that so far have not received much research attention. Searching the part of the molecule that is responsible for transport ability of Hsp70, we found a cationic sequence composed of 20 amino acid residues on its surface, KST peptide, which was used in further experiments. We showed that KST peptide enters living cells of various origins with the same efficiency as the full-length chaperone. KST peptide is capable of carrying cargo with a molecular weight 30 times greater than its own into cells. When we compared the membrane-crossing activity of KST peptide in complex with Avidin (KST–Av complex) with that of similarly linked canonical TAT peptide, we found that TAT peptide penetrated SK-N-SH human neuroblastoma cells at a similar rate and efficiency as the KST peptide. Furthermore, KST peptide can carry protein complexes consisting of a specific antibody coupled to the peptide through the Avidin bridge. An antibody to Hsp70 delivered to SK-N-SH cells with high expression level of Hsp70 reduced the protective power of the chaperone and sensitized the cells to the pro-apoptotic effect of staurosporine. We studied the mechanisms of penetration of KST–Av and full-length Hsp70 inside human neuroblastoma SK-N-SH and human erythroleukemia K-562 cells and found that both used an active intracellular transport mechanism that included vesicular structures and negatively charged lipid membrane domains. Competition analysis of intracellular transport showed that the chaperone reduced intracellular penetration of KST peptide and conversely KST peptide prevented Hsp70 transport in a dose-dependent manner.

Electronic supplementary material

The online version of this article (doi:10.1007/s12192-014-0554-z) contains supplementary material, which is available to authorized users.     

Hsp70/nitric oxide relationship in apoptotic modulation during obstructive nephropathy

The functional integrity of the kidney depends on normal development as well as on physiological cell turnover. Apoptosis induction is essential for these mechanisms. Multiple mechanisms are unleashed during obstructive nephropathy, one of the most complex being programmed cell death that leads to renal tubular atrophy and tubular loss. This review will focus on the interaction of nitric oxide and Hsp70 and on the regulation of renal antiapoptotic and protective oxidative stress responses.     

Hsp70蛋白自身磷酸化对其分子伴侣功能的影响

近年对分子伴侣蛋白Hsp70作用机制的研究发现,其ATP功能区域X光晶体结构有一个新的钙离子结合区域,这个新的功能区域与Hsp70分子的ADP结合、ATP水解及合成有关.有报道认为Hsp70蛋白的NDP激酶样作用,通过形成酸不稳定性自身磷酸化中间体催化γ 磷酸基团在ATP和ADP间传递,组氨酸H89与这个新的区域有密切关系,有可能与Hsp70蛋白形成自身磷酸化中间体有关.本研究运用基因定位诱导突变技术,将89位组氨酸以丝氨酸替代(H89S),通过比较Hsp70野生型及突变型蛋白的自身磷酸化过程的改变,及其对Hsp70蛋白体外荧光素酶活性影响的不同,初步探讨Hsp70作用机制.结果发现,突变的H89S蛋白自身磷酸化过程及体外变性荧光素酶重折叠受到抑制.野生型蛋白未受到影响,野生型Hsp70可以形成酸不稳定的自身磷酸化中间体,产生CDP依赖性解磷酸反应,而H89S突变型蛋白不能形成这种反应.89位组氨酸点突变能显著降低ATP酶交换反应及体外变性荧光素酶重折叠水平,但它的自身磷酸化可能并非唯一必需的介导位点或只是一个选择性的功能侧链.     

Ku70乙酰化介导TSA诱导的结肠癌细胞凋亡

目的:探讨组蛋白去乙酰化酶抑制剂(HDI)trichostatin A(TSA)对Ku70的乙酰化及其在TSA诱导结肠癌细胞凋亡中的作用。方法:以TSA处理结肠癌细胞HCT116和HT29细胞,采用免疫沉淀结合Western blot检测TSA对Ku70乙酰化的作用,流式细胞术检测TSA诱导的细胞凋亡,Western blot检测凋亡相关蛋白Bax和细胞色素c(cytochrom c)的转位和表达。结果:TSA可引起结肠癌HCT116和HT29细胞Ku70乙酰化,并与凋亡密切相关,与对照组相比,HCT116凋亡率(P=0.007)和HT29细胞凋亡率(P=0.005)均显著增高,免疫共沉淀检测到TSA处理细胞后,Bax和Ku70之间的相互作用减弱,表明TSA引起的乙酰化促进Bax从Bax-Ku70复合物中释放,Western blot结果显示TSA促进Bax由胞浆向线粒体转位,同时促进cytochrom c由线粒体向胞浆转位。结论:Ku70乙酰化作用介导了TSA诱导的结肠癌细胞凋亡。     

HSP70和JNK信号转导通路在肝癌组织中的表达及意义

目的探讨HSP70和JNK信号转导通路在肝癌组织中的作用,以及它们之间的关系。方法用SP免疫组化方法检测62例肝癌组织中HSP70、JNK1、JNK2和c-Jun的表达。应用SSPS统计软件进行数据处理。结果(1)HSP70蛋白1级染色16例(25.8%),2级染色25例(40.3%),3级染色21例(33.9%)。JNK1、JNK2和c-Jun蛋白低表达分别为40例(64.5%)、33例(53.2%)和36例(58.1%),高表达分别为22例(35.5%)、29例(46.8%)和26例(41.9%)。(2)HSP70蛋白表达与肝癌分化程度呈正相关(r=0.449,P=0.000),JNK1、JNK2和c-Jun蛋白表达均与肝癌分化程度呈负相关(r=-0.351,P=0.005;r=-0.303,P=0.017;r=-0.302,P=0.017)。(3)HSP70蛋白的表达与JNK1(r=-0.385,P=0.002)、JNK2(r=-0.309,P=0.015)和c-Jun(r=-0.302,P=0.017)蛋白的表达呈负相关。(4)Kaplan-Meier法生存分析发现HSP70和JNK1蛋白的表达与术后无复发生存时间密切相关(P<0.01)。(5)多因素Cox比例风险模型分析,结果HSP70与预后明显相关(P=0.004)。结论HSP70蛋白与肝癌的进展和预后密切相关。JNK信号转导通路与肝癌的分化有关。HSP70可能通过抑制JNK信号传导途径,而阻断由其介导的肝癌细胞的凋亡,提高了肝癌细胞在应激状态下的稳定性。     

Hsp70, a messenger from hyperthermia for the immune system

Heat shock proteins (Hsps) hold a dual role depending on their location. Inside cells, they fulfill essential survival functions as molecular chaperones forming complexes with intracellular polypeptides (self or foreign) to help in protein folding, the resolution of protein aggregates and intracellular protein transport. Released from the cell, they act as messengers communicating the cells’ interior protein composition to the immune system for initiation of immune responses against intracellular proteins. Here we describe the mechanisms by which Hsp70, the heat-inducible Hsp70 family member, crosstalks with the immune system. Further, we discuss that clinical hyperthermia could be a way to initiate the immunologic activity of Hsp70 by upregulating its expression and facilitating release through local necrosis.     

Induction of biochemical stress markers and apoptosis in transgenic Drosophila melanogaster against complex chemical mixtures: role of reactive oxygen species

The study was aimed to investigate the effect of leachates of solid waste from a flashlight battery factory and a pigment plant on 70 kDa heat shock protein (Hsp70) expression, generation of reactive oxygen species (ROS), antioxidant enzymes activities and apoptosis in Drosophila. Third instar larvae of Drosophila melanogaster transgenic for hsp70 (hsp70-lacZ) were fed on diet mixed with leachates of solid wastes (0.05-2.0%, v/v) released from two industrial plants at three different pHs (7.00, 4.93 and 2.88) for 2-48 h. A concentration- and time-dependent significant change in Hsp70 expression, ROS generation, antioxidant enzymes activities and MDA content was observed in the exposed larvae preceding the antioxidant enzymes activities. Mitochondria-mediated, caspase-dependent apoptotic cell death in the larvae exposed to 1.0 and 2.0% leachates of flashlight battery factory was concurrent with a significant regression in Hsp70 expression and a higher ROS generation. A positive correlation drawn between ROS generation and apoptotic markers and a negative correlation between apoptotic markers and Hsp70 expression in these groups indicated the important role of ROS in the leachate-induced cellular damage. Hsp70 along with antioxidant enzymes offered protection to the organisms exposed to all the tested concentrations of the leachates of pigment plant waste and 0.5% leachate of flashlight battery factory in a cooperative manner when ROS generation was less induced. Conversely, higher levels of ROS generation in the organisms treated with 1.0 and 2.0% leachate of flashlight battery factory after 24 and 48 h resulted in regression of Hsp70 expression in them leading to cell death. The study suggests that (1) leachates of flashlight battery factory waste more adversely affected the organisms in comparison to the leachates of pigment plant waste. (2) Hsp70 may be used as a biomarker of cellular damage in organisms exposed to leachates. (3) Cell based assays using D. melanogaster as an in vivo model may provide important mechanistic information about the adverse effect of xenobiotics.     

预热诱导心肌细胞表达Hsp70对Fas通路活化后细胞凋亡变化的研究

目的:研究Hsp70对Fas通路活化后细胞凋亡的作用及其可能机制.方法:水浴预热诱导培养新生大鼠心肌细胞Hsp70表达,Fas抗体活化Fas通路,Western blot测定Hsp70的表达,流式细胞仪检测细胞凋亡率,特异性底物测定caspase-8及caspase-3的活力.结果:预热可以使心肌细胞Hsp70表达升高,Fas抗体降低细胞凋亡率,高表达Hsp70可以降低Fas通路活化后心肌细胞凋亡率,同时相应使caspase-8及caspase-3活力升高的幅度降低.结论:Hsp70可能通过抑制caspase-8及caspase-3的活力而降低Fas通路活化后培养新生大鼠心肌细胞凋亡的发生.     

Hsp70 regulates the doxorubicin-mediated heart failure in Hsp70-transgenic mice

The aim of this study was to investigate the potential protective effect of the Hsp70 protein in the cardiac dysfunction induced by doxorubicin (DOX) and the mechanisms of its action. For this purpose, we used both wild-type mice (F1/F1) and Hsp70-transgenic mice (Tg/Tg) overexpressing human HSP70. Both types were subjected to chronic DOX administration (3 mg/kg intraperitoneally every week for 10 weeks, with an interval from weeks 4 to 6). Primary cell cultures isolated from embryos of these mice were also studied. During DOX administration, the mortality rate as well as weight reduction were lower in Tg/Tg compared to F1/F1 mice (P < 0.05). In vivo cardiac function assessment by transthoracic echocardiography showed that the reduction in left ventricular systolic function observed after DOX administration was lower in Tg/Tg mice (P < 0.05). The study in primary embryonic cell lines showed that the apoptosis after incubation with DOX was reduced in cells overexpressing Hsp70 (Tg/Tg), while the apoptotic pathway that was activated by DOX administration involved activated protein factors such as p53, Bax, caspase-9, caspase-3, and PARP-1. In myocardial protein extracts from identical mice with DOX-induced heart failure, the particular activated apoptotic pathway was confirmed, while the presence of Hsp70 appeared to inhibit the apoptotic pathway upstream of the p53 activation. Our results, in this DOX-induced heart failure model, indicate that Hsp70 overexpression in Tg/Tg transgenic mice provides protection from myocardial damage via an Hsp70-block in p53 activation, thus reducing the subsequent apoptotic mechanism.     

益生菌联合柳氮磺胺吡啶治疗溃疡性结肠炎的疗效观察

【摘 要】 目的 通过建立葡聚糖硫酸钠(DSS)诱导的急性期溃疡性结肠炎(UC)小鼠模型,观察嗜酸乳杆菌以及联合柳氮磺胺吡啶对小鼠溃疡性结肠炎(UC)的治疗作用,并检测Hsp70、Hsp27在肠黏膜的表达,探讨其可能的作用机制。方法　5% DSS 7 d建立急性UC动物模型。将60只BALB/c小鼠随机分为6组：正常对照组、模型组、阴性对照(生理盐水,NS)组、嗜酸乳杆菌组、柳氮磺胺吡啶组和嗜酸乳杆菌联合柳氮磺胺吡啶组,观察指标包括：疾病活动指数(DAI)、结肠黏膜肉眼改变及病理组织学积分;采用免疫组化SABC 法检测热休克蛋白(HSP70)和(HSP27)的表达量。结果 嗜酸乳杆菌可降低实验小鼠DAI积分和改善结肠组织损伤;与模型组、阴性对照组相比,嗜酸乳杆菌联合柳氮磺胺吡啶组的HSP70表达增加(P＜0.05),其中以嗜酸乳杆菌联合柳氮磺胺吡啶组效果最佳。结论 嗜酸乳杆菌和柳氮磺胺吡啶对小鼠溃疡性结肠炎都有治疗作用,且二者疗效相当;两药联合应用效果最佳。其机制可能与增加结肠黏膜HSP70的表达有关。     

Involvement of the ubiquitin pathway in decreasing Ku70 levels in response to drug-induced apoptosis

Ku70 plays an important role in DNA damage repair and prevention of cell death. Previously, we reported that apoptosis caused a decrease in cellular Ku70 levels. In this study, we analyzed the mechanism of how Ku70 levels decrease during drug-induced apoptosis. In HeLa cells, staurosporin (STS) caused a decrease in Ku70 levels without significantly affecting Ku70 mRNA levels. We found that Ku70 protein was highly ubiquitinated in various cell types, such as HeLa, HEK293T, Dami (a megakaryocytic cell line), endothelial, and rat kidney cells. An increase in ubiquitinated Ku70 protein was observed in apoptotic cells, and proteasome inhibitors attenuated the decrease in Ku70 levels in apoptotic cells. These results suggest that the ubiquitin-proteasome proteolytic pathway plays a role in decreasing Ku70 levels in apoptotic cells. Ku70 forms a heterodimer with Ku80, which is required for the DNA repair activity of Ku proteins. We also found that Ku80 levels decreased in apoptotic cells and that Ku80 is a target of ubiquitin. Ubiquitinated Ku70 was not found in the Ku70-Ku80 heterodimer, suggesting that modification by ubiquitin inhibits Ku heterodimer formation. We propose that the ubiquitin-dependent modification of Ku70 plays an important role in the control of cellular levels of Ku70.     

Nmi interacts with Hsp105β and enhances the Hsp105β-mediated Hsp70 expression

The mammalian stress protein Hsp105α is expressed constitutively and is further induced under stress conditions, whereas the alternative spliced form, Hsp105β is only expressed during mild heat shock. We previously reported that Hsp105α is localized mainly in the cytoplasm, whereas Hsp105β is localized in the nucleus. Consistent with the different localization of these proteins, Hsp105β but not Hsp105α induces the expression of the major stress protein Hsp70. We here identified N-myc and Stat interactor (Nmi), as an Hsp105β-binding protein by yeast two-hybrid screening. Immunoprecipitation and pull-down assay showed that Nmi interacts with Hsp105β in vivo and in vitro. Luciferase reporter gene assay and Western blotting showed that Nmi enhanced both the Hsp105β-induced phosphorylation of Stat3 and the Hsp105β-induced activation of the hsp70 promoter in a manner that is dependent on the Stat3-binding site, which results in an increase in Hsp70 protein levels. Most importantly, mild heat shock-induced Hsp70 expression, which is dependent on Hsp105β, is suppressed by knockdown of endogenous Nmi. These results suggest that Nmi has a role as a positive regulator of Hsp105β-mediated hsp70 gene expression along the Stat3 signaling pathway.     

The association of CaM and Hsp70 regulates S-phase arrest and apoptosis in a spatially and temporally dependent manner in human cells

The cell cycle is controlled by regulators functioning at the right time and at the right place. We have found that calmodulin (CaM) has specific distribution patterns during different cell-cycle stages. Here, we identify cell-cycle-specific binding proteins of CaM and examine their function during cell-cycle progression. We first applied immunoprecipitation methods to isolate CaM-binding proteins from cell lysates obtained at different cell-cycle phases and then identified these proteins using mass spectrometry methods. A total of 41 proteins were identified including zinc finger proteins, ribosomal proteins, and heat shock proteins operating in a Ca²⁺-dependent or independent manner. Fifteen proteins were shown to interact with CaM in a cell-phase-specific manner. The association of the selected proteins and CaM were confirmed with in vitro immunoprecipitation and immunostaining methods. One of the identified proteins, heat shock protein 70 (Hsp70), was further studied with respect to its cell-cycle-related function. In vivo fluorescence resonance energy transfer (FRET) analysis showed that the interaction of CaM and Hsp70 was found in the nucleus during the S phase. Overexpression of Hsp70 is shown to arrest cells at S phase and, thus, induce cell apoptosis. When we disrupted the CaM-Hsp70 association with HSP70 truncation without the CaM-binding domain, we found that S-phase arrest and apoptosis could be rescued. The results suggest that the spatial and temporal association of CaM and Hsp70 can regulate cell-cycle progression and cell apoptosis.