Heat Shock Factor 1 Overexpression Research Articles

Heat shock factor 1 suppresses the HIV-induced inflammatory response by inhibiting nuclear factor-κB

The persistent inflammation aggravated by a disordered immune response is considered to be the major cause of CD4+ T cell depletion in lymphoid tissue, which impels the progression of AIDS. Here, we report that heat shock factor 1 (HSF1) works as an innate repressor of HIV-induced inflammation. The activation of HSF1 was found to accompany inflammation during HIV infection. Further research uncovered that HSF1 activation inhibited HIV-induced inflammation. In addition, HSF1 overexpression suppressed the inflammatory response induced by HIV, while HSF1 deficiency exacerbated that inflammation. Mechanistically, HSF1 was found to compete with nuclear factor-κB (NF-κB) in the nucleus. Generally, our report highlights that HSF1 is an important host factor in regulating HIV-induced inflammation and may work as a potential target for curing AIDS.

Heat Shock Factor 1 Predicts Poor Prognosis of Gastric Cancer.

PurposeHeat shock factor 1 (HSF1) is a key regulator of the heat shock response and plays an important role in various cancers. However, the role of HSF1 in gastric cancer is still unknown. The present study evaluated the function of HSF1 and related mechanisms in gastric cancer.Materials and MethodsThe expression levels of HSF1 in normal and gastric cancer tissues were compared using cDNA microarray data from the NCBI Gene Expression Omnibus (GEO) dataset. The proliferation of gastric cancer cells was analyzed using the WST assay. Transwell migration and invasion assays were used to evaluate the migration and invasion abilities of gastric cancer cells. Protein levels of HSF1 were analyzed using immunohistochemical staining of tissue microarrays from patients with gastric cancer.ResultsHSF1 expression was significantly higher in gastric cancer tissue than in normal tissue. Knockdown of HSF1 reduced the proliferation, migration, and invasion of gastric cancer cells, while HSF1 overexpression promoted proliferation, migration, and invasion of gastric cancer cells. Furthermore, HSF1 promoted the proliferation of gastric cancer cells in vivo. In Kaplan-Meier analysis, high levels of HSF1 were associated with poor prognosis for patients with gastric cancer (p=0.028).ConclusionHSF1 may be closely associated with the proliferation and motility of gastric cancer cells and poor prognosis of patients with gastric cancer. Accordingly, HSF1 could serve as a prognostic marker for gastric cancer.

Abstract 21075: Heat Shock Factor 1 Modulates Exosomes Biogenesis and Cargo

Introduction: Cardiac Progenitor cells (CPCs, identified by ckit+/CD45-/lin-) are being used in 21 clinical trials (recruiting and completed) to restore heart function and promote tissue regeneration in response to injury and their exosomes (EXO) has been identified to be critical for their functional activity. Hypothesis: We hypothesized that heat shock factor 1 (HSF1) modulates EXO biogenesis from CPCs and their enrichment with therapeutic miRs. Methods and Results: EXOs were isolated from cultured CPCs, generated from the biopsies of right atrial appendage (RAA) at the time of cardiac surgery from neonatal (nCPCs, < 1 month) and adult (aCPCs, > 40 years) patients with normal functioning myocardium using size exclusion chromatography (CL-2B). EXOs were analyzed by transmission electron microscopy, Nanosight (LM10) and the flow cytometry for EXO markers as CD63 and ALIX. Our results showed that physiological changes as ageing affects EXOs biogenesis and their functional potential as nCPCs generate significantly more EXOs than aCPCs. HSF1 overexpression in aCPCs significantly enhanced their EXO biogenesis. nCPCs derived EXOs (nEXOs) are significantly more effective (nEXOs 62.14±2.9% vs aEXO 56 ± 3.6%, p<0.05) to improve cardiac function and tissue repair in a myocardial infarction (MI) model in rats as compared to aCPCs derived EXOs. In a rat MI model, using florescent labelled HLA-A antibodies, nEXOs were identified to be retained for longer duration in rat serum as compared to aEXOs, which correlated with myocardial functional recovery. miRNA sequencing of EXOs identified significantly higher expression of cardio protective miRs like miR199a, 146a, 454, 590, 130a in nEXOs as compared to aEXOs. We also identified that HSF1 overexpression in aCPCs significantly enriched them with miR199a, miR130a and miR590 suggesting that HSF1 can affect EXO biogenesis and its miR Cargo. The results of large scale production of EXOs using hollow fibre systems will also be presented. Conclusion: We showed that nEXOs are functionally more active and modulation of HSF1 can affect EXOs biogenesis and its cargo from CPCs. These results also suggest that nEXOs has the potential to be utilized as an off the shelf cell-free therapy.

Abstract 197: Heat Shock Factor 1 Enhances Therapeutic Potential of c-kit+ Cardiac Progenitor Cells Derived Exosomes

Background: Cardiac Progenitor cells (CPCs, identified by ckit+/CD45-/lin-) are being studied in 21 clinical trials (recruiting and completed) to restore heart function and promote tissue regeneration in response to injury. We have recently identified that CPCs derived exosomes (EXO) are critical for their functional activity. Hypothesis: We hypothesized that heat shock factor 1 (HSF1) modulates EXO biogenesis from CPCs and their enrichment with therapeutic miRs. Methods and Results: EXOs were isolated from cultured CPCs, generated from the biopsies of right atrial appendage (RAA) at the time of cardiac surgery from neonatal (nCPCs, < 1 month) and adult (aCPCs, > 40 years) patients with normal functioning myocardium using size exclusion chromatography (CL-2B). EXOs were analyzed by transmission electron microscopy, Nanosight (LM10) and the flow cytometry for EXO markers as CD63 and ALIX. Our results showed that chronological ageing affects EXOs biogenesis and their functional potential since nCPCs generate significantly more EXOs than aCPCs. HSF1 overexpression in aCPCs significantly enhanced their EXO biogenesis. nCPCs derived EXOs (nEXOs) are significantly more effective (nEXOs 62.14±2.9% vs aEXO 56 ± 3.6%, p<0.05) to improve cardiac function and tissue repair in a myocardial infarction (MI) model in rats as compared to aCPCs derived EXOs. In a rat MI model, using florescent labelled HLA-A antibodies, nEXOs were retained for longer duration in rat serum as compared to aEXOs, which correlated with myocardial functional recovery. miRNA sequencing of EXOs identified significantly higher expression of cardio protective miRs like miR199b, 146a, 454, 590, 21 in nEXOs as compared to aEXOs. We also identified that HSF1 overexpression in aCPCs significantly enriched them with miR21 and miR590, suggesting that HSF1 can affect EXO biogenesis and its miR Cargo. Conclusion: We showed that nEXOs are functionally more active and modulation of HSF1 can affect EXOs biogenesis and its cargo from CPCs. These results also suggest that nEXOs has the potential to be utilized as an off the shelf cell-free therapy.

Hepatic Activation of the FAM3C-HSF1-CaM Pathway Attenuates Hyperglycemia of Obese Diabetic Mice.

FAM3C is a member of the family with sequence similarity 3 (FAM3) gene family, and this study determined its role and mechanism in regulation of hepatic glucose/lipid metabolism. In obese diabetic mice, FAM3C expression was reduced in the liver, and hepatic FAM3C restoration improved insulin resistance, hyperglycemia, and fatty liver. FAM3C overexpression increased the expression of heat shock factor 1 (HSF1), calmodulin (CaM), and phosphorylated protein kinase B (Akt) and reduced that of gluconeogenic and lipogenic genes in diabetic mouse livers with the suppression of gluconeogenesis and lipid deposition. In cultured hepatocytes, FAM3C overexpression upregulated HSF1 expression, which elevated CaM protein level by inducing CALM1 transcription to activate Akt in a Ca2+- and insulin-independent manner. Furthermore, FAM3C overexpression promoted nuclear exclusion of FOXO1 and repressed gluconeogenic gene expression and gluconeogenesis in a CaM-dependent manner in hepatocytes. Hepatic HSF1 overexpression activated the CaM-Akt pathway to repress gluconeogenic and lipogenic gene expression and improve hyperglycemia and fatty liver in obese diabetic mice. In conclusion, the FAM3C-HSF1-CaM-Akt pathway plays important roles in regulating glucose and lipid metabolism in hepatocytes independent of insulin and calcium. Restoring hepatic FAM3C expression is beneficial for the management of type 2 diabetes and fatty liver.

Overexpression of heat shock factor 1 maintains TAR DNA binding protein 43 solubility via induction of inducible heat shock protein 70 in cultured cells.

TAR DNA binding protein 43 (TDP-43) is a nuclear protein that has been shown to have altered homeostasis in the form of neuronal nuclear and cytoplasmic aggregates in some familial and almost all cases of sporadic amyotrophic lateral sclerosis as well as 51% of frontotemporal lobar degeneration and 57% of Alzheimer's disease cases. Heat shock proteins (HSPs), such as HSP70, recognize misfolded or aggregated proteins and refold, disaggregate, or turn them over and are upregulated by the master transcription factor heat shock factor 1 (HSF1). Here, we explore the effect of HSF1 overexpression on proteotoxic stress-related alterations in TDP-43 solubility, proteolytic processing, and cytotoxicity. HSF1 overexpression reduced TDP-43-positive puncta concomitantly with upregulating HSP70 and HSP90 protein levels. HSF1 overexpression or pharmacological activation sustained TDP-43 solubility and significantly reduced truncation of TDP-43 in response to inhibition of the proteasome with Z-Leu-Leu-Leu-al, and this was reversed by HSF1 inhibition. HSF1 activation conferred protection against toxicity associated with TDP-43 C-terminal fragments without globally increasing the activity of the ubiquitin proteasome system (UPS) while concomitantly reducing the induction of autophagy, suggesting that HSF1 protection is an early event. In support of this, inhibition of HSP70 ATPase activity further reduced TDP-43 solubility. HSF1 knockout significantly increased TDP-43 insolubility and accelerated TDP-43 fragmentation in response to proteotoxic stress. Overall, this study shows that HSF1 overexpression protects against TDP-43 pathology by upregulation of chaperones, especially HSP70, rather than enhancing autophagy or the UPS during times of proteotoxic stress. © 2016 Wiley Periodicals, Inc.

The Impact of Hyperthermia on Receptor-Mediated Interleukin-6 Regulation in Mouse Skeletal Muscle.

In inflammatory cells, hyperthermia inhibits lipopolysaccharide (LPS)-induced interleukin-6 (IL-6) gene expression and protein secretion. Since hyperthermia alone stimulates IL-6 in skeletal muscle, we hypothesized that it would amplify responses to other receptor-mediated stimuli. IL-6 regulation was tested in C2C12 myotubes and in soleus during treatment with epinephrine (EPI) or LPS. In EPI-treated myotubes (100 ng/ml), 1 h exposure at 40.5°C-42°C transiently increased IL-6 mRNA compared to EPI treatment alone at 37°C. In LPS-treated myotubes (1 μg/ml), exposure to 41°C-42°C also increased IL-6 mRNA. In isolated mouse soleus, similar amplifications of IL-6 gene expression were observed in 41°C, during both low (1 ng/ml) and high dose (100 ng/ml) EPI, but only in high dose LPS (1 μg/ml). In myotubes, heat increased IL-6 secretion during EPI exposure but had no effect or inhibited secretion with LPS. In soleus there were no effects of heat on IL-6 secretion during either EPI or LPS treatment. Mechanisms for the effects of heat on IL-6 mRNA were explored using a luciferase-reporter in C2C12 myotubes. Overexpression of heat shock factor-1 (HSF-1) had no impact on IL-6 promoter activity during EPI stimulation, but elevated IL-6 promoter activity during LPS stimulation. In contrast, when the activator protein-1 (AP-1) element was mutated, responses to both LPS and EPI were suppressed in heat. Using siRNA against activating transcription factor-3 (ATF-3), a heat-stress-induced inhibitor of IL-6, no ATF-3-dependent effects were observed. The results demonstrate that, unlike inflammatory cells, hyperthermia in muscle fibers amplifies IL-6 gene expression to EPI and LPS. The effect appears to reflect differential engagement of HSF-1 and AP-1 sensitive elements on the IL-6 gene, with no evidence for involvement of ATF-3. The functional significance of increased IL-6 mRNA expression during heat may serve to overcome the well-known suppression of protein synthetic pathways occurring during heat shock.

Heat shock factor 1 induces cancer stem cell phenotype in breast cancer cell lines.

Heat shock factor 1 (HSF1) has long been recognized as the master transcription factor that regulates heat shock proteins (HSPs). More recently HSF1 has been associated with a broader role in regulating response to a variety of cellular stresses beyond heat-shock. We previously found that high HSF1 expression is associated with poor outcome in lung, breast and colon cancers. Importantly, however, the HSF1 signature correlated with poor outcome in these studies was not related to the heat shock response, which suggested that tumor outcome associated with high HSF expression may be due to processes other than stress response. Hence, we explored the question whether high HSF1 expression might be associated with the cancer stem cell (CSC) phenotype. To do so, we examined the association of HSF1 with CSC phenotype by FACS and immunofluorescence. In addition, we evaluated the effects of HSF1 over-expression and knock-down on sphere formation and CSC marker expression in breast cancer cell lines. Here, we report results demonstrating that high HSF1 not only correlates with CSC marker expression, but inducible HSF1 over-expression augments and HSF1 knock-down inhibits CSC phenotype. Furthermore, HSF1 expression confers resistance to chemotherapeutic drugs and increases CSC frequency. In conclusion, our study indicates that one of the potential HSP-independent HSF1 driven mechanisms that may contribute to poor outcome in human tumors involves regulation of the CSC phenotype. Hence, therapeutic inhibition of HSF1 may be one route to target CSCs in human tumors.Electronic supplementary materialThe online version of this article (doi:10.1007/s10549-015-3521-1) contains supplementary material, which is available to authorized users.

Upregulation of Nuclear Heat Shock Factor 1 Contributes to Tumor Angiogenesis and Poor Survival in Patients With Non–Small Cell Lung Cancer

The aim of this study was to detect the expression of heat shock factor 1 (HSF1) and microvessel density (MVD) in patients with non-small cell lung cancer (NSCLC) and to examine the relevance between HSF1 and angiogenesis, clinicopathologic factors, and prognosis. Immunohistochemical staining was used to examine the level of expression of HSF1 and CD34. MVD was used to detect the number of microvessels by counting CD34(+) endothelial cells. Their relationship with clinicopathologic factors and prognosis in patients with NSCLC was determined using IBM SPSS Statistics, version 19 (SPSS Inc, Chicago, IL). The level of expression of HSF1 was increased significantly in NSCLC. HSF1 overexpression was observed in 45 patients and was significantly associated with MVD (p= 0.005). The overexpression of HSF1 was not associated with patient sex, age, tumor size, histologic type, or differentiation, but it was significantly associated with node metastasis (p= 0.005) and clinical stage (p=0.006). HSF1 overexpression and high MVD were significantly associated with poor 5-year disease-free survival (p= 0.001 and p= 0.006, respectively). Patients with HSF1 overexpression and high MVD had a significantly poor overall survival (p= 0.006 and p= 0.019, respectively) and disease-specific survival (p= 0.005 and p= 0.016, respectively). Multivariate analysis showed that HSF1 overexpression was an independent prognosticator for poor overall, disease-specific, and disease-free survival (p= 0.040, p= 0.046, and p= 0.004, respectively). Overexpression of HSF1 is common and significantly correlated with tumor angiogenesis in NSCLC. Patients with high HSF1 expression had poorer overall, disease-free, and disease-specific survival. These current findings suggest that HSF1 may serve as a novel prognostic marker and potential therapeutic target molecule for antiangiogenic therapy in patients with NSCLC.

HSF1 functions as a transcription regulator for Dp71 expression.

Heat shock factor 1 (HSF1) is one of the most important transcriptional molecules in the heat shock process; however, HSF1 can also regulate the expression of other proteins. Dystrophin Dp71 is one of the most widely expressed isoforms of the dystrophin gene family. In our experiments, we showed for the first time that HSF1 can function as a transcriptional factor for endogenous Dp71 expression in vivo and in vitro. We demonstrated that the messenger RNA (mRNA) and protein expression of Dp71 were significantly reduced in HSF1-knockout mice compared with wild-type mice in brain, lung, liver, spleen, and kidney. Overexpression of HSF1 significantly enhanced the mRNA and protein expression of Dp71 in HeLa cells. Inhibiting the expression of HSF1 in HeLa cells significantly reduced the expression of Dp71. By use of the EMSA technique, the chromatin immunoprecipitation assay, and the luciferase reporter system, we demonstrated that HSF1 can directly bind the HSE in the Dp71 promoter region. We concluded from our data that HSF1 functions as a transcriptional regulator of Dp71 expression.

HSF1 deficiency and impaired HSP90-dependent protein folding are hallmarks of aneuploid human cells.

Aneuploidy is a hallmark of cancer and is associated with malignancy and poor prognosis. Recent studies have revealed that aneuploidy inhibits proliferation, causes distinct alterations in the transcriptome and proteome and disturbs cellular proteostasis. However, the molecular mechanisms underlying the changes in gene expression and the impairment of proteostasis are not understood. Here, we report that human aneuploid cells are impaired in HSP90-mediated protein folding. We show that aneuploidy impairs induction of the heat shock response suggesting that the activity of the transcription factor heat shock factor 1 (HSF1) is compromised. Indeed, increased levels of HSF1 counteract the effects of aneuploidy on HSP90 expression and protein folding, identifying HSF1 overexpression as the first aneuploidy-tolerating mutation in human cells. Thus, impaired HSF1 activity emerges as a critical factor underlying the phenotypes linked to aneuploidy. Finally, we demonstrate that deficient protein folding capacity directly shapes gene expression in aneuploid cells. Our study provides mechanistic insight into the causes of the disturbed proteostasis in aneuploids and deepens our understanding of the role of HSF1 in cytoprotection and carcinogenesis.

Heat shock factor 1 is required for migration and invasion of human melanoma in vitro and in vivo

Heat shock factor 1 (HSF1) is a major transactivator of the heat shock response. Recent studies have demonstrated that HSF1 is involved in tumor initiation, maintenance, and progression by regulating the expression of heat shock proteins (HSPs) and other molecular targets. Furthermore, HSF1 was identified as a potent proinvasion oncogene in human melanomas. However, the biological functions of HSF1 in human melanoma remain poorly understood. To determine the functional role of HSF1 in melanoma, we used short hairpin RNA (shRNA) to silence HSF1 in human melanoma cell lines and investigated its effect on cell migration and invasive ability in vitro. We found that HSF1 knockdown led to a marked reduction in migration and invasive ability, and these functions were restored by overexpression of wild-type HSF1. To confirm the in vitro results, we performed subcutaneous xenograft experiments in athymic nude mice. We found that HSF1 was required for melanoma invasion and metastasis, as well as tumorigenic potential in vivo. Overall, these results show that HSF1 is indispensable for melanoma progression and metastasis, and suggests that HSF1 could be a promising therapeutic target for melanoma.

SPICING THING UP – WHAT CAN WE LEARN FROM SYNTHETIC CANNABINOIDS ABOUT THE LINK BETWEEN CANNABINOIDS AND PSYCHOSIS

Heat shock factor 1 (HSF1) is a major transactivator of the heat shock response. Recent studies have demonstrated that HSF1 is involved in tumor initiation, maintenance, and progression by regulating the expression of heat shock proteins (HSPs) and other molecular targets. Furthermore, HSF1 was identified as a potent proinvasion oncogene in human melanomas. However, the biological functions of HSF1 in human melanoma remain poorly understood. To determine the functional role of HSF1 in melanoma, we used short hairpin RNA (shRNA) to silence HSF1 in human melanoma cell lines and investigated its effect on cell migration and invasive ability in vitro. We found that HSF1 knockdown led to a marked reduction in migration and invasive ability, and these functions were restored by overexpression of wild-type HSF1. To confirm the in vitro results, we performed subcutaneous xenograft experiments in athymic nude mice. We found that HSF1 was required for melanoma invasion and metastasis, as well as tumorigenic potential in vivo. Overall, these results show that HSF1 is indispensable for melanoma progression and metastasis, and suggests that HSF1 could be a promising therapeutic target for melanoma.

Akt phosphorylates and activates HSF-1 independent of heat shock, leading to Slug overexpression and epithelial–mesenchymal transition (EMT) of HER2-overexpressing breast cancer cells

Epithelial-mesenchymal transition (EMT) is an essential step for tumor progression, although the mechanisms driving EMT are still not fully understood. In an effort to investigate these mechanisms, we observed that heregulin-mediated activation of HER2, or HER2 overexpression, resulted in EMT, which is accompanied with increased expression of a known EMT regulator Slug, but not TWIST or Snail. We then investigated how HER2 induced Slug expression and found, for the first time, that there are four consensus HSF Sequence-binding Elements (HSEs), the binding sites for heat shock factor-1 (HSF-1), located in the Slug promoter. HSF-1 bound to and transactivated the Slug promoter independent of heat shock, leading to Slug expression in breast cancer cells. Mutation of the putative HSEs ablated Slug transcriptional activation induced by heregulin or HSF-1 overexpression. Knockdown of HSF-1 expression by siRNA reduced Slug expression and heregulin-induced EMT. The positive association between HSF-1 and Slug was confirmed by immunohistochemical staining of a cohort of 100 invasive breast carcinoma specimens. While investigating how HER2 activated HSF-1 independent of heat shock, we observed that HER2 activation resulted in concurrent phosphorylation of Akt and HSF-1. We then observed, also for the first time, that Akt directly interacted with HSF-1 and phosphorylated HSF-1 at S326. Inhibition of Akt using siRNA, dominant-negative Akt mutant, or small molecule inhibitors prevented heregulin-induced HSF-1 activation and Slug expression. Conversely, constitutively active Akt induced HSF-1 phosphorylation and Slug expression. HSF-1 knockdown reduced the ability of Akt to induce Slug expression, indicating an essential that HSF-1 plays in Akt-induced Slug upregulation. Together, our study uncovered the existence of a novel Akt-HSF-1 signaling axis that leads to Slug upregulation and EMT, and potentially contributes to progression of HER2-positive breast cancer.

Curcumin augments the efficacy of antitumor drugs used in leukemia by modulation of heat shock proteins via HDAC6.

Heat shock proteins (HSPs) and histone deacetylase 6 (HDAC6) are induced under oxidative stress, which promotes oncogenesis. HSPs are regulated by heat shock factor1 (HSF1). HDAC6, a class IIb deacetylase, plays an essential role in tumorigenesis and cell stress response. HSPs, HSF1 and HDAC6 are up-regulated in cancer. In the present study, we explored the effect of curcumin, a phytochemical, on HSPs (27, 70, 90), HSF1 and HDAC6 in two different leukemia cell lines (K-562 and HL-60). The association between HDAC6, HSPs, and intrinsic oxidative stress was also investigated. Overexpression of HSPs (27, 70, 90), HSF1, and HDAC6 in leukemia cells were down-regulated by curcumin, and the effects on HSPs 27and 70 were less than that on HSP 90. This resulted in cell cycle arrest at the G2/M stage, leading to apoptosis. Different cell cycle regulatory proteins (p53, p21, cyclin B1, CDK1, Cdc25C) and some apoptosis-related proteins (Bcl-2, Bax, Bid, Bad, Apaf1, AIF and Cyt c) were altered by curcumin. Increased ROS levels in leukemia cells were quenched by curcumin. A probable association between high ROS level and the overexpression of the tumor markers was established in this study. Thus, curcumin enhanced the efficacy of anti-tumor drugs imatinib-mesylate and cytarabine through the inhibition of the tumor markers.

Heat shock factor 1 over-expression protects against exposure of hydrophobic residues on mutant SOD1 and early mortality in a mouse model of amyotrophic lateral sclerosis

BackgroundMutations in the Cu/Zn superoxide dismutase gene (SOD1) are responsible for 20% of familial forms of amyotrophic lateral sclerosis (ALS), and mutant SOD1 has been shown to have increased surface hydrophobicity in vitro. Mutant SOD1 may adopt a complex array of conformations with varying toxicity in vivo. We have used a novel florescence-based proteomic assay using 4,4’-bis-1-anilinonaphthalene-8-sulfonate (bisANS) to assess the surface hydrophobicity, and thereby distinguish between different conformations, of SOD1and other proteins in situ.ResultsCovalent bisANS labeling of spinal cord extracts revealed that alterations in surface hydrophobicity of H46R/H48Q mutations in SOD1 provoke formation of high molecular weight SOD1 species with lowered solubility, likely due to increased exposure of hydrophobic surfaces. BisANS was docked on the H46R/H48Q SOD1 structure at the disordered copper binding and electrostatic loops of mutant SOD1, but not non-mutant WT SOD1. 16 non-SOD1 proteins were also identified that exhibited altered surface hydrophobicity in the H46R/H48Q mutant mouse model of ALS, including proteins involved in energy metabolism, cytoskeleton, signaling, and protein quality control. Heat shock proteins (HSPs) were also enriched in the detergent-insoluble fractions with SOD1. Given that chaperones recognize proteins with exposed hydrophobic surfaces as substrates and the importance of protein homeostasis in ALS, we crossed SOD1 H46R/H48Q mutant mice with mice over-expressing the heat shock factor 1 (HSF1) transcription factor. Here we showed that HSF1 over-expression in H46R/H48Q ALS mice enhanced proteostasis as evidenced by increased expression of HSPs in motor neurons and astrocytes and increased solubility of mutant SOD1. HSF1 over-expression significantly reduced body weight loss, delayed ALS disease onset, decreases cases of early disease, and increased survival for the 25th percentile in an H46R/H48Q SOD1 background. HSF1 overexpression did not affect macroautophagy in the ALS background, but was associated with maintenance of carboxyl terminus of Hsp70 interacting protein (CHIP) expression which declined in H46R/H48Q mice.ConclusionOur results uncover the potential importance of changes in protein surface hydrophobicity of SOD1 and other non-SOD1 proteins in ALS, and how strategies that activate HSF1 are valid therapies for ALS and other age-associated proteinopathies.

Heat shock factor 1 accelerates hepatocellular carcinoma development by activating nuclear factor-κB/mitogen-activated protein kinase

Heat shock factor 1 (HSF1), a major transactivator of stress responses, has been implicated in carcinogenesis in various organs. However, little is known about the biological functions of HSF1 in the development of hepatocellular carcinoma (HCC). To clarify the functional role of HSF1 in HCC, we established HSF1-knockdown (HSF1 KD) KYN2 HCC cells by stably expressing either small hairpin RNA (shRNA) against HSF1 (i.e. HSF1 KD) or control shRNA (HSF1 control). Tumorigenicity was significantly reduced in orthotopic mice with HSF1 KD cells compared with those with HSF1 control cells. Reduced tumorigenesis in HSF1 KD cells appeared attributable to increased apoptosis and decreased proliferation. Tumor necrosis factor-α-induced apoptosis was increased in HSF1 KD cells and HSF1(-/-) mouse hepatocytes compared with controls. Decreased expression of IκB kinase γ, a positive regulator of nuclear factor-κB, was also observed in HSF1 KD cells and HSF1(-/-) mouse hepatocytes. Furthermore, expression of bcl-2-associated athanogene domain 3 (BAG3) was dramatically reduced in HSF1 KD cells and HSF1(-/-) mouse hepatocytes. We also found that epidermal growth factor-stimulated mitogen-activated protein kinase signaling was impaired in HSF1 KD cells. Clinicopathological analysis demonstrated frequent overexpression of HSF1 in human HCCs. Significant correlations between HSF1 and BAG3 protein levels and prognosis were also observed. In summary, these results identify a mechanistic link between HSF1 and liver tumorigenesis and may provide as a potential molecular target for the development of anti-HCC therapies.

Skeletal muscle interleukin-6 regulation in hyperthermia

We previously reported that IL-6 production is acutely elevated in skeletal muscles exposed to ≥41°C, but the regulatory pathways are poorly understood. The present study characterizes the heat-induced transcriptional control of IL-6 in C2C12 muscle fibers. Hyperthermia exposure (42°C for 1 h) induced transcription from an IL-6 promoter-luciferase reporter plasmid. Heat shock factor-1 (HSF-1), a principal mediator of the heat shock response, was then tested for its role in IL-6 regulation. Overexpression of a constitutively active HSF-1 construct increased basal (37°C) promoter activity, whereas overexpression of a dominant negative HSF-1 reduced IL-6 promoter activity during basal and hyperthermia conditions. Since hyperthermia also induces stress-activated protein kinase (SAPK) signaling, we tested whether mutation of a transcription site downstream of SAPK, (i.e., activator protein-1, AP-1) influences IL-6 transcription in hyperthermia. The mutation had no effect on baseline reporter activity but completely inhibited heat-induced activity. We then tested whether pharmacologically induced states of protein stress, characteristic of cellular responses to hyperthermia and known to induce SAPKs and HSF-1, would induce IL-6 production in the absence of heat. The proteasome was inhibited with MG-132 in one set of experiments, and the unfolded protein response was stimulated with dithiothreitol, thapsigargin, tunicamycin, or castanospermine in other experiments. All treatments stimulated IL-6 protein secretion in the absence of hyperthermia. These studies demonstrate that IL-6 regulation in hyperthermia is directly controlled by HSF-1 and AP-1 signaling and that the IL-6 response in C2C12 myotubes is sensitive to categories of protein stress that reflect accumulation of damaged or unfolded proteins.

Heavy metal response of the heat shock protein 70 gene is mediated by duplicated heat shock elements and heat shock factor 1

Heavy metals induce transcription of a number of mammalian genes, but in most cases the mechanism of induction has not been well characterized. The human heat shock protein 70 gene (hsp70) is activated by several heavy metals such as Cd and Zn, and the heat shock element (HSE) has been proposed to mediate metal response by previous studies. However, it was observed that the lack of further upstream sequences rendered the hsp70 promoter unresponsive to metals. A detailed deletion analysis of the promoter revealed that the distal HSE-like sequence (dHSE) is required for heavy metal response. A supershift assay showed that the heat shock factor 1 (HSF1) recognized dHSE, as well as the proximal HSE (pHSE). An hsp70 promoter variant with a dHSE mutation that blocks HSF1 binding completely lost metal response, demonstrating that the HSF1/dHSE interaction is crucial. Another promoter variant with a similar pHSE mutation partially lost metal response, indicating that both HSEs are required for full activity. Knockdown of HSF1 dramatically reduced the metal response of hsp70, demonstrating its essential role. Furthermore, a reporter gene regulated by the human hsp70 promoter, which lacked metal response in HSF1-null mouse cells, acquired the response upon over-expression of a recombinant human HSF1. These results demonstrate that the duplicated HSEs and HSF1 constitute the mechanism for the heavy metal response of hsp70, which is distinct from the known metal regulatory system for the metallothionein genes.

A Novel mouse model of enhanced proteostasis: Full-length human heat shock factor 1 transgenic mice

The heat shock response (HSR) is controlled by the master transcriptional regulator heat shock factor 1 (HSF1). HSF1 maintains proteostasis and resistance to stress through production of heat shock proteins (HSPs). No transgenic model exists that overexpresses HSF1 in tissues of the central nervous system (CNS). We generated a transgenic mouse overexpressing full-length non-mutant HSF1 and observed a 2–4-fold increase in HSF1 mRNA and protein expression in all tissues studied of HSF1 transgenic (HSF1 +/0) mice compared to wild type (WT) littermates, including several regions of the CNS. Basal expression of HSP70 and 90 showed only mild tissue-specific changes; however, in response to forced exercise, the skeletal muscle HSR was more elevated in HSF1 +/0 mice compared to WT littermates and in fibroblasts following heat shock, as indicated by levels of inducible HSP70 mRNA and protein. HSF1 +/0 cells elicited a significantly more robust HSR in response to expression of the 82 repeat polyglutamine-YFP fusion construct (Q82YFP) and maintained proteasome-dependent processing of Q82YFP compared to WT fibroblasts. Overexpression of HSF1 was associated with fewer, but larger Q82YFP aggregates resembling aggresomes in HSF1 +/0 cells, and increased viability. Therefore, our data demonstrate that tissues and cells from mice overexpressing full-length non-mutant HSF1 exhibit enhanced proteostasis.