scholarly journals The HSP90 inhibitor Onalespib exerts synergistic anti-cancer effects when combined with radiotherapy: an in vitro and in vivo approach

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Diana Spiegelberg ◽  
Andris Abramenkovs ◽  
Anja Charlotte Lundgren Mortensen ◽  
Sara Lundsten ◽  
Marika Nestor ◽  
...  
Keyword(s):  
Tumor Growth ◽  
External Beam Radiotherapy ◽  
Heat Shock Protein 90 ◽  
Hsp90 Inhibitor ◽  
Control Group ◽  
A431 Cells ◽  
Anti Cancer ◽  
Client Proteins

AbstractOncogenic client-proteins of the chaperone Heat shock protein 90 (HSP90) insure unlimited tumor growth and are involved in resistance to chemo- and radiotherapy. The HSP90 inhibitor Onalespib initiates the degradation of oncoproteins, and might also act as a radiosensitizer. The aim of this study was therefore to evaluate the efficacy of Onalespib in combination with external beam radiotherapy in an in vitro and in vivo approach. Onalespib downregulated client proteins, lead to increased apoptosis and caused DNA-double-strands. Monotherapy and combination with radiotherapy reduced colony formation, proliferation and migration assessed in radiosensitive HCT116 and radioresistant A431 cells. In vivo, a minimal treatment regimen for 3 consecutive days of Onalespib (3 × 10 mg/kg) doubled survival, whereas Onalespib with radiotherapy (3 × 2 Gy) caused a substantial delay in tumor growth and prolonged the survival by a factor of 3 compared to the HCT116 xenografted control group. Our results demonstrate that Onalespib exerts synergistic anti-cancer effects when combined with radiotherapy, most prominent in the radiosensitive cell models. We speculate that the depletion and downregulation of client proteins involved in signalling, migration and DNA repair mechanisms is the cause. Thus, individually, or in combination with radiotherapy Onalespib inhibits tumor growth and has the potential to improve radiotherapy outcomes, prolonging the overall survival of cancer patients.

Heat Shock Protein 90 Inhibitor NVP-AUY922 Has Potent Anti-Tumor Activity With Adult T-Cell Leukemia-Lymphoma Cells

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1829-1829
Author(s):  
Hiroaki Taniguchi ◽  
Hiroo Hasegawa ◽  
Daisuke Sasaki ◽  
Koji Ando ◽  
Yasushi Sawayama ◽  
...  
Keyword(s):  
T Cell ◽  
Cell Survival ◽  
Cell Lines ◽  
Heat Shock Protein 90 ◽  
Hsp90 Inhibitor ◽  
Adult T Cell Leukemia ◽  
Pim Kinases ◽  
Client Proteins

Abstract Background Adult T-cell leukemia-lymphoma (ATL) is a chemo-resistant malignancy. Heat shock protein 90 (HSP90) is involved in folding and functions as a chaperone for multiple client proteins, many of which are important in tumorigenesis. The HSP90 inhibitor 17-AAG, derived from geldanamycin, has potent antitumor activity against ATL. However, geldanamycin derivatives have several limitations, including poor solubility, formulation difficulties, and severe hepatotoxicity in clinical settings, which have prompted development of second generation synthetic HSP90 inhibitors including NVP-AUY922 (AUY922), a second generation isoxazole-based non-geldanamycin HSP90 inhibitor that inhibits the ATPase activity of HSP90. AUY922 has shown nanomolar efficacy against a wide range of human cancer cells in vitro and also inhibits progression of a variety of tumors in vivo. Phase I/II studies of AUY922 with advanced solid tumors and hematological malignancies are presently underway. Here, we studied the effects of AUY922 on ATL in vitro and in vivo. Results We initially analyzed the effects of AUY922 (Novartis Pharmaceuticals) on survival of ATL-derived cell lines (KK1, SO4, LM-Y1, KOB, ST1) and HTLV-I-infected T-cell lines (MT2, HuT102). Cells cultured with various concentrations of AUY922 for 72 hours showed survival suppression in a dose-dependent manner in MTS assay findings. The concentrations of AUY922 required to inhibit cell survival by 50% (IC50) varied from 12.5 to 25.0 nM. We also found that the inhibitory effect of AUY was superior to that of 17-AAG. We further assessed AUY922-induced cell survival inhibition with peripheral blood mononuclear cells (PBMCs) obtained from patients with ATL and healthy donors. AUY922 induced apparent cell survival suppression in primary ATL cells, but not in normal PBMCs, while FACS analysis revealed that AUY922 induced cell-cycle arrest and apoptosis in these cell lines. Interestingly, AUY922 induced down-regulation of PIM kinases, which was confirmed by DNA microarray, qRT-PCR, and WB analysis results. Furthermore, SGI-1776, a PIM kinase inhibitor, successfully induced cell survival suppression in ATL and HTLV-1 infected cell lines in both dose- and cell-dependent manners. To elucidate the molecular mechanisms of cytotoxicity, we also examined the expressions of several client proteins using WB analysis. AUY922 treatment led to strong up-regulation of HSP70, a surrogate marker of HSP90 inhibition, and a dose-dependent decrease of HSP90 client proteins associated with cell survival, proliferation, and cell cycle in the G1 phase, including p-Akt, Akt, IκBα, IKKα, IKKβ, IKKγ, Cdk4, Cdk6, and survivin. In a xenograft model created with C.B-17/Icr-SCID mice, intraperitoneal administration of the vehicle or AUY922 was given after injection of HuT102 cells. In the control mice, bulky tumors grew within 4 weeks, whereas daily administrations of AUY922 significantly impaired tumor growth. Conclusion Together, our findings suggest that AUY922 may be an effective therapeutic agent for ATL and PIM kinases are a novel therapeutic target. Disclosures: No relevant conflicts of interest to declare.

scholarly journals A Brain Penetrating Heat-Shock Protein 90 Inhibitor NXD30001 Inhibits Glioblastoma as a Monotherapy or in Combination With Radiation

Neurosurgery ◽  
2019 ◽  
Vol 66 (Supplement_1) ◽  
Author(s):  
Hao Chen ◽  
Jialiang Wang ◽  
Hengli Tian
Keyword(s):  
Stem Cells ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Median Survival ◽  
Therapeutic Potential ◽  
Heat Shock Protein 90 ◽  
Tumor Bearing ◽  
Client Proteins

Abstract INTRODUCTION It has been increasingly recognized that glioblastoma multiforme (GBM) is a highly heterogeneous disease, which is initiated and sustained by molecular alterations in an array of signal transduction pathways. Heat-shock protein 90 (Hsp90) is a molecular chaperone to be critically implicated in folding and activation of a diverse group of client proteins, many of which are key regulators of important glioblastoma biology. METHODS To determine the therapeutic potential of targeting Hsp90 in glioblastoma, we assessed the anti-neoplastic efficacy of NXD30001, a brain-penetrating Hsp90 inhibitor as a monotherapy or in combination with radiation, both in Vitro and in Vivo. RESULTS Our results demonstrated that NXD30001 potently inhibited neurosphere formation, growth and survival of CD133 + glioblastoma stem cells (GSCs) with the half maximal inhibitory concentrations (IC50) at low nanomolar concentrations. At suboptimal concentrations, inhibition of Hsp90 did not exert cytotoxic activity but rather increased radiosensitivity in GSCs. CD133- GBM cells were less sensitive and not radiosensitized by NXD30001. In lines with its cytotoxic and radiosensitizing effects, NXD30001 dose-dependently decreased phosphorylation protein levels of multiple Hsp90 client proteins, including those playing key roles in GSCs, such as EGFR, Akt, c-Myc, and Notch1. In addition, combining NXD30001 with radiation could impair DNA damage response and ER stress response to induce apoptosis of GSCs. Treatment of orthotopic glioblastoma tumors with NXD30001 extended median survival of tumor-bearing mice by approximately 20% (treated 37 days vs vehicle 31 d, P = .0026). Radiation alone increased median survival of tumor-bearing mice from 31 to 38 d, combination with NXD30001 further extended survival to 43 d (P = .0089). CONCLUSION Our results suggest that GBM stem cells (CD133+) are more sensitive to NXD30001 than non-stem GBM cells (CD133-). Furthermore, combination NXD30001 with radiation significantly inhibits GBM progression than use it as a monotherapy by targeting GSCs.

scholarly journals Sildenafil triggers tumor lethality through altered expression of HSP90 and degradation of PKD2

2020 ◽  
Vol 41 (10) ◽  
pp. 1421-1431 ◽  
Author(s):  
Lu Chen ◽  
Yang Liu ◽  
Alexander Becher ◽  
Kristina Diepold ◽  
Evi Schmid ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Cancer Cells ◽  
Hsp90 Inhibitor ◽  
Altered Expression ◽  
Cancer Subtypes ◽  
Low Concentrations ◽  
Underlying Mechanisms ◽  
Approved Drugs

Abstract The repurposing of existing drugs has emerged as an attractive additional strategy to the development of novel compounds in the fight against cancerous diseases. Inhibition of phosphodiesterase 5 (PDE5) has been claimed as a potential approach to target various cancer subtypes in recent years. However, data on the treatment of tumors with PDE5 inhibitors as well as the underlying mechanisms are as yet very scarce. Here, we report that treatment of tumor cells with low concentrations of Sildenafil was associated with decreased cancer cell proliferation and augmented apoptosis in vitro and resulted in impaired tumor growth in vivo. Notably, incubation of cancer cells with Sildenafil was associated with altered expression of HSP90 chaperone followed by degradation of protein kinase D2, a client protein previously reported to be involved in tumor growth. Furthermore, the involvement of low doses of PU-H71, an HSP90 inhibitor currently under clinical evaluation, in combination with low concentrations of Sildenafil, synergistically and negatively impacted on the viability of cancer cells in vivo. Taken together, our study suggests that repurposing of already approved drugs, alone or in combination with oncology-dedicated compounds, may represent a novel cancer therapeutic strategy.

Evaluation of Anti-Tumor Potential of Lactobacillus acidophilus ATCC4356 Culture Supernatants in MCF-7 Breast Cancer

2020 ◽  
Vol 21 ◽  
Author(s):  
Ramazan Behzadi ◽  
Ahmad Hormati ◽  
Karim Eivaziatashbeik ◽  
Sajjad Ahmadpour ◽  
Fatemeh Khodadust ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Nude Mice ◽  
Control Group ◽  
Bacterial Strains ◽  
Anti Cancer ◽  
99Mtc Mibi ◽  
Culture Supernatants ◽  
Mcf 7

Background: Anti-cancer activity of some lactic acid bacterial strains is well documented in several literatures. Lactobacillus strains have received considerable attention as a beneficial microbiota. The aim of this study is to evaluate the effects of anti-tumor activities of L. acidophilus ATCC4356 culture supernatants on the MCF-7 human breast cancer cells. Materials and methods: Anti-cancer effect of 24h and 48h culture supernatants at various concentrations (1.25, 2.5, 5, 10 and 20 µg/ml) were determined by various in vitro and in vivo assays including MTT, tumor volume measurement as well as 99mTc-MIBI biodistribution in MCF-7 tumor bearing nude mice and histopathology test. For evaluation of the related mechanism of action, quantitative PCR was conducted. Results: The 48h culture supernatants at 10 and 20 µg/ml exhibited significant in vitro inhibition of MCF-7 cell proliferation. However, this inhibition was not observed for HUVEC human endothelial normal cells. Q-PCR indicated that treatment by the supernatant led to a significant downregulation of VEGFR ( ̴ 0.009 fold) and Bcl-2 ( ̴ 0.5 fold) and upregulation of p53 ( ̴ 1.3 fold). In vivo study using MCF-7 xenograft mouse models demonstrated reduction in tumor weight and volume by both 24h and 48h supernatants (10 µg/ml and 20 µg/ml) after 15 days. According to the 99mTc-MIBI biodistribution result, treatment of MCF-7 bearing nude mice with both 24h and 48h supernatant (20 µg/ml) led to significant decrease in tumor uptake compared with the control group. Conclusion: These results suggest that the culture supernatants of L. acidophilus ATCC4356 at suitable concentrations can be considered as a good alternative nutraceutical with promising therapeutic indexes for breast cancer.

A Novel Heat Shock Protein (HSP) 90 Inhibitor KW-2478 shows Activity in B-Cell Malignancies in Vitro and in Vivo.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1625-1625
Author(s):  
Simone Juliger ◽  
Takayuki Nakashima ◽  
Lenushka Maharaj ◽  
Toshihiko Ishii ◽  
Hiroshi Nakagawa ◽  
...  
Keyword(s):  
Cell Growth ◽  
B Cell ◽  
Cell Lines ◽  
Cell Lymphoma ◽  
Hsp90 Inhibitor ◽  
Anti Tumour Activity ◽  
Client Proteins ◽  
Tumour Activity

Abstract Background : HSP90 plays an important role in chaperoning key proteins implicated in malignant disease and is a promising therapeutic target. We now report the in vitro and in vivo activity of a novel HSP90 inhibitor of non-ansamycin, non-purine analogue class, KW-2478, (Kyowa Hakko Kirin) in B-cell malignancies including multiple myeloma (MM), B-cell lymphoma (BCL) and mantle cell lymphoma (MCL) cells, and in primary tumour cells from MM and BCL patients. Procedures: The binding affinity of KW-2478 to HSP90 was examined using immobilised human HSP90a and a biotinylated HSP90 binding agent, radicicol (bRD). The effect of KW-2478 on cell viability, cell growth and apoptosis induction were evaluated in cell lines, with KW-2478 induced changes in major HSP90 client proteins studied by Western blotting analysis. The in vivo anti-tumour activity of KW-2478 was evaluated in a human MM xenograft mouse model,. Primary MM cells were studied using a co-culture system with the HS-5 bone marrow stromal cell line (BMSCs), while primary BCL samples were cultured on CHO cells stably transfected to produce CD40L. Results: KW-2478 inhibited the binding of bRD to HSP90α in concentration-dependent manner with an IC50 value of 3.8 nM. KW-2478 clearly inhibited cancer cell growth in all cell lines, with EC50 values from 101–252 nM in BCL, 81.4–91.4 nM in MCL and 120–622 nM in MM. The drug also exhibited potent growth inhibitory activity in primary CLL (n=3) and NHL (n=2) cells with EC50 values of 40–170 nM and 200–400 nM, respectively. In 2 of 4 human primary myeloma cells, KW-2478 at 2 μM inhibited cell growth by at least 50%. The presence of BMSCs did not affect drug activity against primary MM cells and importantly there was little or no effect on cell number or viability of normal BMSCs at up to 20 μM KW-2478. Exposure of MM and BCL cell lines to KW-2478 for 24 hours resulted in the degradation of HSP90 client proteins (IGF-1Rβ and Raf-1) and the induction of HSP70. KW-2478 also induced PARP cleavage and dephosphorylated Erk1/2 in NCI-H929 cells. Further studies in selected cell lines showed that exposure to 1 μM KW-2478 or lower resulted in the depletion of p53 and Akt proteins, a reduction in nuclear NFKB, and the cleavage of caspase-3. In the NCI-H929 xenograft model, KW-2478 (qd×5, i.v.) showed a statistically significant suppression of tumour growth at the doses of 25, 50, 100 and 200 mg/kg. Moreover, tumour regressions were observed at doses of 100 and 200 mg/kg, with a significant decrease in serum M protein concentration at doses of 50, 100 and 200 mg/kg. No severe KW-2478 toxicity was observed as assessed by treatment-related mortality and body weight change. Conclusions: The novel HSP90 inhibitor KW-2478 showed a potent anti-tumour activity both in vitro and in vivo, including activity in primary patient samples. The agent retained its activity in primary myeloma cells in the presence of BMSCs, suggesting that KW-2478 can overcome the protective effect of the bone marrow microenvironment. Additional pharmacokinetic and safety data support the further development of KW-2478 and the drug is currently undergoing clinical evaluation in a phase I trial.

scholarly journals Rosiglitazone impairs proliferation of human adrenocortical cancer: preclinical study in a xenograft mouse model

2010 ◽  
Vol 17 (1) ◽  
pp. 169-177 ◽  
Author(s):  
Michaela Luconi ◽  
Monica Mangoni ◽  
Stefania Gelmini ◽  
Giada Poli ◽  
Gabriella Nesi ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Day Treatment ◽  
Xenograft Model ◽  
Preclinical Study ◽  
Histological Evaluation ◽  
Control Group ◽  
Adrenocortical Cancer ◽  
Ki 67

Adrenocortical carcinoma (ACC) is a rare aggressive tumor with a poor prognosis. The lack of a specific and effective medical treatment is due to the poor knowledge of the mechanisms underlying tumor growth. Research on potential drugs able to specifically interfere with tumor proliferation is essential to develop more efficacious therapies. We evaluated for the first time the in vivo effect of rosiglitazone (RGZ), an anti-diabetic drug with in vitro anti-tumor properties, on ACC proliferation in a xenograft model obtained by s.c. injection of human ACC H295R cells in athymic mice. When the tumor size reached 5 mm, animals were allocated to 5 mg/kg RGZ- or water-treated groups. Tumor volume was measured twice a week. A significant reduction of tumor growth in RGZ versus control (control) group was observed and was already maximal following 17 day treatment (1−T/C=75.4% (43.7–93.8%)). After 31 days of treatment, mice were killed and tumor analyzed. Tumor histological evaluation revealed characteristics of invasiveness, richness in small vessels and mitotic figures in control group, while RGZ group tumors presented non infiltrating borders, few vessels, and many apoptotic bodies. Tumor immunohistochemistry showed that Ki-67 was reduced in RGZ versus control group. Quantitative real-time RT-PCR demonstrated a significant reduction in the expression of angiogenic (VEGF), vascular (CD31), proliferation (BMI-1), and anti-apoptotic (Bcl-2) genes in RGZ versus control group tumors. The same inhibitory effects were confirmed in in vitro RGZ-treated H295R. Our findings support and expand the role of RGZ in controlling ACC proliferation and angiogenesis in vivo and in vitro.

scholarly journals Definition of the minimal fragments of Sti1 required for dimerization, interaction with Hsp70 and Hsp90 and in vivo functions

2007 ◽  
Vol 404 (1) ◽  
pp. 159-167 ◽  
Author(s):  
Gary Flom ◽  
Robert H. Behal ◽  
Luke Rosen ◽  
Douglas G. Cole ◽  
Jill L. Johnson
Keyword(s):  
Current Model ◽  
Heat Shock Protein 90 ◽  
C Terminus ◽  
Client Proteins ◽  
Definition Of ◽  
Necessary And Sufficient ◽  
In Vitro Interaction

The molecular chaperone Hsp (heat-shock protein) 90 is critical for the activity of diverse cellular client proteins. In a current model, client proteins are transferred from Hsp70 to Hsp90 in a process mediated by the co-chaperone Sti1/Hop, which may simultaneously interact with Hsp70 and Hsp90 via separate TPR (tetratricopeptide repeat) domains, but the mechanism and in vivo importance of this function is unclear. In the present study, we used truncated forms of Sti1 to determine the minimal regions required for the Hsp70 and Hsp90 interaction, as well as Sti1 dimerization. We found that both TPR1 and TPR2B contribute to the Hsp70 interaction in vivo and that mutations in both TPR1 and TPR2B were required to disrupt the in vitro interaction of Sti1 with the C-terminus of the Hsp70 Ssa1. The TPR2A domain was required for the Hsp90 interaction in vivo, but the isolated TPR2A domain was not sufficient for the Hsp90 interaction unless combined with the TPR2B domain. However, isolated TPR2A was both necessary and sufficient for purified Sti1 to migrate as a dimer in solution. The DP2 domain, which is essential for in vivo function, was dispensable for the Hsp70 and Hsp90 interaction, as well as Sti1 dimerization. As evidence for the role of Sti1 in mediating the interaction between Hsp70 and Hsp90 in vivo, we identified Sti1 mutants that result in reduced recovery of Hsp70 in Hsp90 complexes. We also identified two Hsp90 mutants that exhibit a reduced Hsp70 interaction, which may help clarify the mechanism of client transfer between the two molecular chaperones.

scholarly journals Hsp90-stabilized MIF supports tumor progression via macrophage recruitment and angiogenesis in colorectal cancer

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Luisa Klemke ◽  
Tiago De Oliveira ◽  
Daria Witt ◽  
Nadine Winkler ◽  
Hanibal Bohnenberger ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Epithelial Cells ◽  
Tumor Growth ◽  
Tumor Progression ◽  
Hsp90 Inhibitor ◽  
Growth Defects ◽  
Macrophage Recruitment ◽  
Upstream Regulator

AbstractMacrophage migration inhibitory factor (MIF) is an upstream regulator of innate immunity, but its expression is increased in some cancers via stabilization with HSP90-associated chaperones. Here, we show that MIF stabilization is tumor-specific in an acute colitis-associated colorectal cancer (CRC) mouse model, leading to tumor-specific functions and selective therapeutic vulnerabilities. Therefore, we demonstrate that a Mif deletion reduced CRC tumor growth. Further, we define a dual role for MIF in CRC tumor progression. Mif deletion protects mice from inflammation-associated tumor initiation, confirming the action of MIF on host inflammatory pathways; however, macrophage recruitment, neoangiogenesis, and proliferative responses are reduced in Mif-deficient tumors once the tumors are established. Thus, during neoplastic transformation, the function of MIF switches from a proinflammatory cytokine to an angiogenesis promoting factor within our experimental model. Mechanistically, Mif-containing tumor cells regulate angiogenic gene expression via a MIF/CD74/MAPK axis in vitro. Clinical correlation studies of CRC patients show the shortest overall survival for patients with high MIF levels in combination with CD74 expression. Pharmacological inhibition of HSP90 to reduce MIF levels decreased tumor growth in vivo, and selectively reduced the growth of organoids derived from murine and human tumors without affecting organoids derived from healthy epithelial cells. Therefore, novel, clinically relevant Hsp90 inhibitors provide therapeutic selectivity by interfering with tumorigenic MIF in tumor epithelial cells but not in normal cells. Furthermore, Mif-depleted colonic tumor organoids showed growth defects compared to wild-type organoids and were less susceptible toward HSP90 inhibitor treatment. Our data support that tumor-specific stabilization of MIF promotes CRC progression and allows MIF to become a potential and selective therapeutic target in CRC.

Dual effects for lovastatin in anaplastic thyroid cancer: the pivotal effect of transketolase (TKT) on lovastatin and tumor proliferation

2018 ◽  
Vol 66 (5) ◽  
pp. 1.4-9 ◽  
Author(s):  
Chih-Yuan Wang ◽  
Hao-Ai Shui ◽  
Tien-Chun Chang
Keyword(s):  
Thyroid Cancer ◽  
Cell Growth ◽  
Protein Expression ◽  
Tumor Growth ◽  
Anaplastic Thyroid Cancer ◽  
Control Group ◽  
Cancer Cell Growth ◽  
Protein Levels

This study tested the hypothesis that the effects of lovastatin on anaplastic thyroid cancer cell growth are mediated by upregulation of transketolase (TKT) expression. The effects of lovastatin on TKT protein levels in ARO cells were determined using western blot and proteomic analyses. After treatment with lovastatin and oxythiamine, the in vitro and in vivo growth of ARO cells was determined using 3-(4,5-Dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assays and tumor xenografts in nude mice. TKT protein expression in the ARO tumors was assessed using immunohistochemistry analysis. Proteomic analysis revealed that 25 µM lovastatin upregulated TKT expression. Co-treatment of ARO cells with 1 µM lovastatin + 1 µM oxythiamine increased TKT protein expression compared with control levels; however, no differences were observed with 10 µM lovastatin + 1 µM oxythiamine. Furthermore, treatment with either oxythiamine or lovastatin alone reduced ARO tumor expression of TKT, as well as decreased ARO cell proliferation in vitro and tumor growth in vivo. However, mice treated with both lovastatin and oxythiamine at the same time had tumor volumes similar to that of the untreated control group. We conclude that either lovastatin or oxythiamine reduced ARO cell growth; however, the combination of these drugs resulted in antagonism of ARO tumor growth.

scholarly journals Functional and physical interaction between yeast Hsp90 and Hsp70

2018 ◽  
Vol 115 (10) ◽  
pp. E2210-E2219 ◽  
Author(s):  
Andrea N. Kravats ◽  
Joel R. Hoskins ◽  
Michael Reidy ◽  
Jill L. Johnson ◽  
Shannon M. Doyle ◽  
...  
Keyword(s):  
Hormone Receptors ◽  
Heat Shock Protein 90 ◽  
Steroid Hormone Receptors ◽  
Physical Interaction ◽  
Mutant Proteins ◽  
Client Proteins ◽  
Protein Remodeling ◽  
The Many

Heat shock protein 90 (Hsp90) is a highly conserved ATP-dependent molecular chaperone that is essential in eukaryotes. It is required for the activation and stabilization of more than 200 client proteins, including many kinases and steroid hormone receptors involved in cell-signaling pathways. Hsp90 chaperone activity requires collaboration with a subset of the many Hsp90 cochaperones, including the Hsp70 chaperone. In higher eukaryotes, the collaboration between Hsp90 and Hsp70 is indirect and involves Hop, a cochaperone that interacts with both Hsp90 and Hsp70. Here we show that yeast Hsp90 (Hsp82) and yeast Hsp70 (Ssa1), directly interact in vitro in the absence of the yeast Hop homolog (Sti1), and identify a region in the middle domain of yeast Hsp90 that is required for the interaction. In vivo results using Hsp90 substitution mutants showed that several residues in this region were important or essential for growth at high temperature. Moreover, mutants in this region were defective in interaction with Hsp70 in cell lysates. In vitro, the purified Hsp82 mutant proteins were defective in direct physical interaction with Ssa1 and in protein remodeling in collaboration with Ssa1 and cochaperones. This region of Hsp90 is also important for interactions with several Hsp90 cochaperones and client proteins, suggesting that collaboration between Hsp70 and Hsp90 in protein remodeling may be modulated through competition between Hsp70 and Hsp90 cochaperones for the interaction surface.

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