Targeted Replacement of HSF1 Phosphorylation Sites at S303/S307 with Alanine Residues in Mice Increases Cell Proliferation and Drug Resistance.

Mammalian heat shock factor HSF1 transcriptional activity is controlled by a multitude of phosphorylations that occur under physiological conditions or following exposure of cells to a variety of stresses. One set of HSF1 phosphorylation is on serine 303 and serine 307 (S303/S307). These HSF1 phosphorylation sites are known to repress its transcriptional activity.

Dusp26 phosphatase regulates mitochondrial respiration and oxidative stress and protects neuronal cell death.

The dual specificity protein phosphatases (Dusps) control dephosphorylation of mitogen-activated protein kinases (MAPKs) as well as other substrates. Here, we report that Dusp26, which is highly expressed in neuroblastoma cells and primary neurons is targeted to the mitochondrial outer membrane via its NH-terminal mitochondrial targeting sequence. Loss of Dusp26 has a significant impact on mitochondrial function that is associated with increased levels of reactive oxygen species (ROS), reduction in ATP generation, reduction in mitochondria motility and release of mitochondrial HtrA2 protease into the cytoplasm.

HSF1-Mediated Control of Cellular Energy Metabolism and mTORC1 Activation Drive Acute T-Cell Lymphoblastic Leukemia Progression.

Deregulated oncogenic signaling linked to PI3K/AKT and mTORC1 pathway activation is a hallmark of human T-cell acute leukemia (T-ALL) pathogenesis and contributes to leukemic cell resistance and adverse prognosis. Notably, although the multiagent chemotherapy of leukemia leads to a high rate of complete remission, options for salvage therapy for relapsed/refractory disease are limited due to the serious side effects of augmenting cytotoxic chemotherapy. We report that ablation of HSF1, a key transcriptional regulator of the chaperone response and cellular bioenergetics, from mouse T-ALL tumors driven by PTEN loss or human T-ALL cell lines, has significant therapeutic effects in reducing tumor burden and sensitizing malignant cell death.

The Molecular Chaperone Heat Shock Protein 70 Controls Liver Cancer Initiation and Progression by Regulating Adaptive DNA Damage and Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase Signaling Pathways.

Delineating the mechanisms that drive hepatic injury and hepatocellular carcinoma (HCC) progression is critical for development of novel treatments for recurrent and advanced HCC but also for the development of diagnostic and preventive strategies. Heat shock protein 70 (HSP70) acts in concert with several cochaperones and nucleotide exchange factors and plays an essential role in protein quality control that increases survival by protecting cells against environmental stressors. Specifically, the HSP70-mediated response has been implicated in the pathogenesis of cancer, but the specific mechanisms by which HSP70 may support malignant cell transformation remains to be fully elucidated.

Modulation of Heat Shock Factor 1 Activity through Silencing of Ser303/Ser307 Phosphorylation Supports a Metabolic Program Leading to Age-Related Obesity and Insulin Resistance.

Activation of the adaptive response to cellular stress orchestrated by heat shock factor 1 (HSF1), which is an evolutionarily conserved transcriptional regulator of chaperone response and cellular bioenergetics in diverse model systems, is a central feature of organismal defense from environmental and cellular stress. HSF1 activity, induced by proteostatic, metabolic, and growth factor signals, is regulated by posttranscriptional modifications, yet the mechanisms that regulate HSF1 and particularly the functional significance of these modifications in modulating its biological activity remain unknown. HSF1 phosphorylation at both Ser303 (S303) and Ser307 (S307) has been shown to repress HSF1 transcriptional activity under normal physiological growth conditions.

Targeted Deletion of Hsf1, 2, and 4 Genes in Mice.

Heat shock transcription factors (Hsfs) regulate transcription of heat shock proteins as well as other genes whose promoters contain heat shock elements (HSEs). There are at least five Hsfs in mammalian cells, Hsf1, Hsf2, Hsf3, Hsf4, and Hsfy (Wu, Annu Rev Cell Dev Biol 11:441-469, 1995; Morimoto, Genes Dev 12:3788-3796, 1998; Tessari et al., Mol Hum Repord 4:253-258, 2004; Fujimoto et al.

WITHDRAWN: Abrogation of heat shock factor 1 (Hsf1) phosphorylation deregulates its activity and lowers activation threshold, leading to obesity in mice.

This article has been withdrawn by the authors. During preparation of this manuscript, a number of errors occurred in the preparation/assembly of Figs 2D, 2E, S1C, S1E, and S4. The authors apologize for not acknowledging that Fig.

The transcriptional regulator of the chaperone response HSF1 controls hepatic bioenergetics and protein homeostasis.

Metabolic energy reprogramming facilitates adaptations to a variety of stress conditions and cellular dysfunction, but how the energetic demands are monitored and met in response to physiological stimuli remains elusive. Our data support a model demonstrating that heat shock factor 1 (HSF1), a master transcriptional regulator of the chaperone response, has been coopted from its role as a critical protein quality-control regulator to having a central role in systemic energy sensing and for metabolic adaptation to nutrient availability. We found that in the absence of HSF1, levels of NAD and ATP are not efficiently sustained in hepatic cells, largely because of transcriptional repression of nicotinamide phosphoribosyltransferase in the NAD salvage pathway.

Therapeutic inducers of the HSP70/HSP110 protect mice against traumatic brain injury.

Traumatic brain injury (TBI) induces severe harm and disability in many accident victims and combat-related activities. The heat-shock proteins Hsp70/Hsp110 protect cells against death and ischemic damage. In this study, we used mice deficient in Hsp110 or Hsp70 to examine their potential requirement following TBI.

An essential role for heat shock transcription factor binding protein 1 (HSBP1) during early embryonic development.

Heat shock factor binding protein 1 (HSBP1) is a 76 amino acid polypeptide that contains two arrays of hydrophobic heptad repeats and was originally identified through its interaction with the oligomerization domain of heat shock factor 1 (Hsf1), suppressing Hsf1's transcriptional activity following stress. To examine the function of HSBP1 in vivo, we generated mice with targeted disruption of the hsbp1 gene and examined zebrafish embryos treated with HSBP1-specific morpholino oligonucleotides. Our results show that hsbp1 is critical for preimplantation embryonic development.

Heat shock factor Hsf1 cooperates with ErbB2 (Her2/Neu) protein to promote mammary tumorigenesis and metastasis.

ErbB2/Neu oncogene is overexpressed in 25% of invasive/metastatic breast cancers. We have found that deletion of heat shock factor Hsf1 in mice overexpressing ErbB2/Neu significantly reduces mammary tumorigenesis and metastasis. Hsf1(+/-)ErbB2/Neu(+) tumors exhibit reduced cellular proliferative and invasive properties associated with reduced activated ERK1/2 and reduced epithelial-mesenchymal transition (EMT).

Inactivation of heat shock factor Hsf4 induces cellular senescence and suppresses tumorigenesis in vivo.

Studies suggest that Hsf4 expression correlates with its role in cell growth and differentiation. However, the role of Hsf4 in tumorigenesis in vivo remains unexplored. In this article, we provide evidence that absence of the Hsf4 gene suppresses evolution of spontaneous tumors arising in p53- or Arf-deficient mice.

Targeted deletion of Hsf1, 2, and 4 genes in mice.

Heat-shock transcription factors (Hsfs) regulate transcription of heat-shock proteins as well as other genes whose promoters contain heat-shock elements. There are at least five Hsfs in mammalian cells, Hsf1, Hsf2, Hsf3, Hsf4, and Hsfy. To understand the physiological roles of Hsf1, Hsf2, and Hsf4 in vivo, we generated knockout mouse lines for these factors.

Heat shock transcription factor 1 is a key determinant of HCC development by regulating hepatic steatosis and metabolic syndrome.

Hepatocellular carcinoma (HCC) occurrence and progression are linked tightly to progressive hepatic metabolic syndrome associated with insulin resistance, hepatic steatosis, and chronic inflammation. Heat shock transcription factor 1 (HSF1), a major transactivator of stress proteins, increases survival by protecting cells against environmental stressors. It has been implicated in the pathogenesis of cancer, but specific mechanisms by which HSF1 supports cancer development remain elusive.

Loss of Hsp110 leads to age-dependent tau hyperphosphorylation and early accumulation of insoluble amyloid beta.

Accumulation of tau into neurofibrillary tangles is a pathological consequence of Alzheimer's disease and other tauopathies. Failures of the quality control mechanisms by the heat shock proteins (Hsps) positively correlate with the appearance of such neurodegenerative diseases. However, in vivo genetic evidence for the roles of Hsps in neurodegeneration remains elusive.

Heat shock factor 1 deficiency via its downstream target gene alphaB-crystallin (Hspb5) impairs p53 degradation.

Heat shock factor Hsf1 regulates the stress-inducibility of heat shock proteins (Hsps) or molecular chaperones. One of the functions attributed to Hsps is their participation in folding and degradation of proteins. We recently showed that hsf1(-/-) cells accumulate ubiquitinated proteins.

Genomic and biological characterization of aggressive and docile strains of lymphocytic choriomeningitis virus rescued from a plasmid-based reverse-genetics system.

Arenaviruses include several causative agents of haemorrhagic fever disease in humans. In addition, the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) is a superb model for the study of virus-host interactions, including the basis of viral persistence and associated diseases. There is little understanding about the molecular mechanisms concerning the regulation and specific role of viral proteins in modulating arenavirus-host cell interactions either associated with an acute or persistent infection, and associated disease.

Regulation of immune response and inflammatory reactions against viral infection by VCAM-1.

The migration of activated antigen-specific immune cells to the target tissues of virus replication is controlled by the expression of adhesion molecules on the vascular endothelium that bind to ligands on circulating lymphocytes. Here, we demonstrate that the adhesion pathway mediated by vascular cell adhesion molecule 1 (VCAM-1) plays a role in regulating T-cell-mediated inflammation and pathology in nonlymphoid tissues, including the central nervous system (CNS) during viral infection. The ablation of VCAM-1 expression from endothelial and hematopoietic cells using a loxP-Cre recombination strategy had no major effect on the induction or overall tissue distribution of antigen-specific T cells during a systemic infection with lymphocytic choriomeningitis virus (LCMV), except in the case of lung tissue.

Control of virus-specific CD8+ T-cell exhaustion and immune-mediated pathology by E3 ubiquitin ligase Cbl-b during chronic viral infection.

A characteristic feature in the immune response to many persistent viral infections is the dysfunction or deletion of antigen-specific T cells (exhaustion). This down-regulation of virus-specific T-cell response represents a critical control mechanism that exists within T-cell activation pathways to prevent lethal disease by inappropriate responses against disseminating virus infections. However, the molecular mechanisms by which the immune system determines whether to mount a full response to such infections remain largely unexplored.

Insights into function and regulation of small heat shock protein 25 (HSPB1) in a mouse model with targeted gene disruption.

The mammalian small heat shock protein (sHSPs) family is comprised of 10 members and includes HSPB1, which is proposed to play an essential role in cellular physiology, acting as a molecular chaperone to regulate diverse cellular processes. Whilst differential roles for sHSPs are suggested for specific tissues, the relative contribution of individual sHSP family members in cellular and organ physiology remains unclear. To address the function of HSPB1 in vivo and determine its tissue-specific expression during development and in the adult, we generated knock-in mice where the coding sequence of hspb1 is replaced by a lacZ reporter gene.

Perforin and Fas cytolytic pathways coordinately shape the selection and diversity of CD8+-T-cell escape variants of influenza virus.

Antigenic variation is a viral strategy exploited to promote survival in the face of the host immune response and represents a major challenge for efficient vaccine development. Influenza viruses are pathogens with high transmissibility and mutation rates, enabling viral escape from immunity induced by prior infection or vaccination. Intense selection from neutralizing antibody drives antigenic changes in the surface glycoproteins, resulting in emergence of new strains able to reinfect hosts immune to previously circulating viruses.

Unique contribution of heat shock transcription factor 4 in ocular lens development and fiber cell differentiation.

Mammalian ocular lens development results via a differentiation program that is highly regulated by tissue-specific transcription factors. Central to this is the terminal differentiation of fiber cells, which develop from epithelial cells on the anterior surface of the lens, accompanied by a change in cell shape and expression of structural proteins (such as membrane proteins MP19, MIP26, connexin 43, 46, and 50, cytoskeletal proteins CP49, CP115, and alpha, beta, and gamma crystallins), creating a transparent, refractive index gradient in the lens. Mutations in genes controlling eye development and in lens structural protein genes are associated with multiple ocular developmental disorders, including cataracts and other opacities of the lens.

TCR affinity and negative regulation limit autoimmunity.

Autoimmune diseases are often mediated by self-reactive T cells, which must be activated to cause immunopathology. One mechanism, known as molecular mimicry, proposes that self-reactive T cells may be activated by pathogens expressing crossreactive ligands. Here we have developed a model to investigate how the affinity of the T-cell receptor (TCR) for the activating agent influences autoimmunity.

Differential tissue-specific regulation of antiviral CD8+ T-cell immune responses during chronic viral infection.

The hallmarks of the immune response to viral infections are the expansion of antigen-specific CD8(+) cytotoxic T lymphocytes (CTLs) after they encounter antigen-presenting cells in the lymphoid tissues and their subsequent redistribution to nonlymphoid tissues to deal with the pathogen. Control mechanisms exist within CTL activation pathways to prevent inappropriate CTL responses against disseminating infections with a broad distribution of pathogen in host tissues. This is demonstrated during overwhelming infection with the noncytolytic murine lymphocytic choriomeningitis virus, in which clonal exhaustion (anergy and/or deletion) of CTLs prevents immune-mediated pathology but allows persistence of the virus.

Essential requirement for both hsf1 and hsf2 transcriptional activity in spermatogenesis and male fertility.

Heat shock factors (Hsfs) are major transactivators of heat shock proteins but are also involved in regulation of other genes active in embryonic development. High expression levels of Hsfs in mouse testis during development suggest a role for these factors in spermatogenesis, a cyclic process of spermatogonia cell-differentiation into mature spermatozoa. In contrast to hsf1(-/-) mice, which exhibit normal spermatogenesis, targeted disruption of hsf2 results in reduced testicular size but only a small impairment in male fertility.