Heat shock response modulators as therapeutic tools for diseases of protein conformation

Molecular characterization of CIRBP from Takifugu fasciatus and its potential roles in cold-induced liver damage

As a potent stressor, environmental cold stress induces severe mitochondrial dysfunction with the overproduction of reactive oxygen species (ROS) in fish, resulting in liver damage. However, the molecular mechanisms underlying the cold-induced liver damage remain unclear. In the present study, the cold-inducible RNA-binding protein (CIRBP) from Takifugu fasciatus was characterized, and its role in cold-induced oxidative stress damage was investigated. An acute liver injury model was constructed by exposing T. fasciatus individuals to temperatures of 25, 19, and 13 °C. Cold exposure markedly induced histomorphological liver injury and triggered endogenous apoptosis and NLRP3 inflammatory response. Cold treatment significantly increased CIRBP gene expression. A similar expression pattern was detected for thioredoxin (TRX), suggesting that these two proteins play a role in the establishment of cold adaptation. CIRBP binds directly to the 3'-UTR of TRX. Furthermore, in vivo experiment showed that, when CIRBP expression in T. fasciatus is knocked down, the time to loss equilibrium significantly shortened at 13 °C. Taken together, our study revealed that CIRBP is a critical protective factor against cold induced liver damage and that the CIRBP/TRX pathway could function as an underlying mechanism for cold adaptation in teleosts.

Isolation and Identification of Yeasts in Marcha, a Rice Wine Starter Culture From Nepal

Nepal harbors a rich diversity of cultures and traditions, including the unique practice of creating an indigenous grain called Marcha by various ethnic groups such as Newar, Tamang, Sherpa, Rai, Limbu, Gurung, Magar, and Tharu people. In the eastern region of Nepal, Marcha producers utilize over 42 different plants, including Vernonia cinerea, Clematis grewiae, Polygala arillata, Buddleja asiatica, Inula sp., Scoparia, and more, which shows regional diversity. The primary objective of the study was to explore the diversity of yeast present in Marcha samples. The studied Marcha samples were collected from 10 different geographic regions of Nepal, which included altogether 27 samples. The isolates were grouped into Groups A, B, and C based on morphological and physiological characteristics. Notably, Group B yeast displayed high amylase production, an enzyme responsible for starch breakdown, and exhibited the ability to produce ethanol. To further investigate the potential of these isolates, stress exclusion tests were conducted, with 30 isolates (70%) showing positive responses. The yeast isolates demonstrated resilience to high glucose concentrations of up to 36% (w/v) at a pH above 3 and a temperature of 37°C, which is the ideal growth condition. The study observed a direct correlation between the yeast isolates' ethanol production capabilities and their tolerance to different ethanol concentrations. Considering that all tested Marcha samples contained yeast capable of starch degradation and ethanol production, it was expected that these yeast isolates would actively participate in the fermentation of starch-based alcohol.

Mapping stress-responsive signaling pathways induced by mitochondrial proteostasis perturbations

Imbalances in mitochondrial proteostasis are associated with pathologic mitochondrial dysfunction implicated in etiologically diverse diseases. This has led to considerable interest in defining the mechanisms responsible for regulating mitochondria in response to mitochondrial stress. Numerous stress-responsive signaling pathways have been suggested to regulate mitochondria in response to proteotoxic stress. These include the integrated stress response (ISR), the heat shock response (HSR), and the oxidative stress response (OSR). Here, we define the stress signaling pathways activated in response to chronic mitochondrial proteostasis perturbations by monitoring the expression of sets of genes regulated downstream of each of these signaling pathways in published Perturb-seq datasets from K562 cells CRISPRi-depleted of mitochondrial proteostasis factors. Interestingly, we find that the ISR is preferentially activated in response to chronic, genetically-induced mitochondrial proteostasis stress, with no other pathway showing significant activation. Further, we demonstrate that CRISPRi depletion of other mitochondria-localized proteins similarly shows preferential activation of the ISR relative to other stress-responsive signaling pathways. These results both establish our gene set profiling approach as a viable strategy to probe stress responsive signaling pathways induced by perturbations to specific organelles and identify the ISR as the predominant stress-responsive signaling pathway activated in response to chronic disruption of mitochondrial proteostasis.

Proteostasis in neurodegenerative diseases

Proteostasis is essential for normal function of proteins and vital for cellular health and survival. Proteostasis encompasses all stages in the "life" of a protein, that is, from translation to functional performance and, ultimately, to degradation. Proteins need native conformations for function and in the presence of multiple types of stress, their misfolding and aggregation can occur. A coordinated network of proteins is at the core of proteostasis in cells. Among these, chaperones are required for maintaining the integrity of protein conformations by preventing misfolding and aggregation and guide those with abnormal conformation to degradation. The ubiquitin-proteasome system (UPS) and autophagy are major cellular pathways for degrading proteins. Although failure or decreased functioning of components of this network can lead to proteotoxicity and disease, like neuron degenerative diseases, underlying factors are not completely understood. Accumulating misfolded and aggregated proteins are considered major pathomechanisms of neurodegeneration. In this chapter, we have described the components of three major branches required for proteostasis-chaperones, UPS and autophagy, the mechanistic basis of their function, and their potential for protection against various neurodegenerative conditions, like Alzheimer's, Parkinson's, and Huntington's disease. The modulation of various proteostasis network proteins, like chaperones, E3 ubiquitin ligases, proteasome, and autophagy-associated proteins as therapeutic targets by small molecules as well as new and unconventional approaches, shows promise.

Mapping Stress-Responsive Signaling Pathways Induced by Mitochondrial Proteostasis Perturbations

Imbalances in mitochondrial proteostasis are associated with pathologic mitochondrial dysfunction implicated in etiologically-diverse diseases. This has led to considerable interest in defining the biological mechanisms responsible for regulating mitochondria in response to mitochondrial stress. Numerous stress responsive signaling pathways have been suggested to regulate mitochondria in response to proteotoxic stress, including the integrated stress response (ISR), the heat shock response (HSR), and the oxidative stress response (OSR). Here, we define the specific stress signaling pathways activated in response to mitochondrial proteostasis stress by monitoring the expression of sets of genes regulated downstream of each of these signaling pathways in published Perturb-seq datasets from K562 cells CRISPRi-depleted of individual mitochondrial proteostasis factors. Interestingly, we find that the ISR is preferentially activated in response to mitochondrial proteostasis stress, with no other pathway showing significant activation. Further expanding this study, we show that broad depletion of mitochondria-localized proteins similarly shows preferential activation of the ISR relative to other stress-responsive signaling pathways. These results both establish our gene set profiling approach as a viable strategy to probe stress responsive signaling pathways induced by perturbations to specific organelles and identify the ISR as the predominant stress-responsive signaling pathway activated in response to mitochondrial proteostasis disruption.

Genetic and Pharmacological Modulation of Cellular Proteostasis Leads to Partial Functional Rescue of Homocystinuria-Causing Cystathionine-Beta Synthase Variants

Homocystinuria (HCU), an inherited metabolic disorder caused by lack of cystathionine beta-synthase (CBS) activity, is chiefly caused by misfolding of single amino acid residue missense pathogenic variants. Previous studies showed that chemical, pharmacological chaperones or proteasome inhibitors could rescue function of multiple pathogenic CBS variants; however, the underlying mechanisms remain poorly understood. Using Chinese hamster DON fibroblasts devoid of CBS and stably overexpressing human WT or mutant CBS, we showed that expression of pathogenic CBS variant mostly dysregulates gene expression of small heat shock proteins HSPB3 and HSPB8 and members of HSP40 family. Endoplasmic reticulum stress sensor BiP was found upregulated with CBS I278T variant associated with proteasomes suggesting proteotoxic stress and degradation of misfolded CBS. Co-expression of the main effector HSP70 or master regulator HSF1 rescued steady-state levels of CBS I278T and R125Q variants with partial functional rescue of the latter. Pharmacological proteostasis modulators partially rescued expression and activity of CBS R125Q likely due to reduced proteotoxic stress as indicated by decreased BiP levels and promotion of refolding as indicated by induction of HSP70. In conclusion, targeted manipulation of cellular proteostasis may represent a viable therapeutic approach for the permissive pathogenic CBS variants causing HCU.

Repression motif in HSF1 regulated by phosphorylation

The heat shock factor 1 (HSF1) is a transcription factor that itself is a sensor for stress and integrates various intrinsic or environmental stress sensing pathways. Thus HSF1 orchestrates the heat shock response (HSR) by translating these pathways into a distinct transcriptional program that aids the cells to cope with and adapt to proteotoxic stress. Although heavily researched the regulation of HSF1 activation is still not completely understood. A conserved reaction to stress is the hyperphosphorylation of the otherwise confined constitutive phosphorylated HSF1. Therefore, this stress specific phosphorylation is believed to be involved in the regulatory mechanism and hence, was and is focus of many studies, ascribing various effects to single phosphorylation sites. To gain additional insight into effects of phosphorylation, HSF1 carrying amino acid substitutions on up to 18 amino acids were tested for their transactivation potential on an HSR reporter plasmid. A pattern of eleven phosphor-mimicking and diminishing amino acid substitutions on well-known phosphorylation sites of HSF1 were introduced to produce transcriptional active [11 M(+)] or repressed [11 M(-)] phenotypes. It could be confirmed that heat activates HSF1 regardless of phosphorylation. Distinct cellular stress, obtained by chemical HSR inducers or mimicked by a constitutively active HSF1, showed clear differences in the activation potential of HSF1-11 M(+) and 11 M(-). Further refinement to the single amino acid level identified the S303/307 double-phosphorylation motif, wherein phosphorylation of S303 was sole responsible for the repressing effect. The effect could be reproduced in different cell lines and is not entirely based on degradation. A small repression motif could be dissociated from the HSF1 context, which is still capable of repressing the background transcription of a specifically designed reporter plasmid. Taken together these results indicate, that besides already described mechanisms of pS303/307 mediated repression of HSF1 activation, an additional mechanism repressing the transcriptional output of the entire HSE containing promoter is mediated by this small repressive motif.

Genetic Deletion of DNAJB3 Using CRISPR-Cas9, Produced Discordant Phenotypes

Several pathways and/or genes have been shown to be dysregulated in obesity-induced insulin resistance (IR) and type 2 diabetes (T2D). We previously showed, for the first time, impaired expression of DNAJB3 mRNA and protein in subjects with obesity, which was concomitant with increased metabolic stress. Restoring the normal expression of DNAJB3 attenuated metabolic stress and improved insulin signaling both in vivo and in vitro, suggesting a protective role of DNAJB3 against obesity and T2D. The precise underlying mechanisms remained, however, unclear. This study was designed to confirm the human studies in a mouse model of dietary obesity-induced insulin resistance, and, if validated, to understand the underlying mechanisms. We hypothesized that mice lacking DNAJB3 would be more prone to high-fat (HF)-diet-induced increase in body weight and body fat, inflammation, glucose intolerance and insulin resistance as compared with wild-type (WT) littermates. Three DNAJB3 knockout (KO) lines were generated (KO 30, 44 and 47), using CRISPR-Cas9. Male and female KO and WT mice were fed a HF diet (45% kcal fat) for 16 weeks. Body weight was measured biweekly, and a glucose tolerance test (GTT) and insulin tolerance test (ITT) were conducted at week 13 and 14, respectively. Body composition was determined monthly by nuclear magnetic resonance (NMR). Following euthanasia, white adipose tissue (WAT) and skeletal muscle were harvested for further analyses. Compared with WT mice, male and female KO 47 mice demonstrated higher body weight and fat mass. Similarly, KO 47 mice also showed a slower rate of glucose clearance in GTT that was consistent with decreased mRNA expression of the GLUT4 gene in WAT but not in the muscle. Both male and female KO 47 mice exhibited higher mRNA levels of the pro-inflammatory marker TNF-a in WAT only, whereas increased mRNA levels of MCP1 chemokine and the ER stress marker BiP/Grp78 were observed in male but not in female KO 47 mice. However, we did not observe the same changes in the other KO lines. Taken together, the phenotype of the DNAJB3 KO 47 mice was consistent with the metabolic changes and low levels of DNAJB3 reported in human subjects. These findings suggest that DNAJB3 may play an important role in metabolic functions and glucose homeostasis, which warrants further phenotyping and intervention studies in other KO 47 and other KO mice, as well as investigating this protein as a potential therapeutic target for obesity and T2D.

Stress Factors as Possible Regulators of Pluripotent Stem Cell Survival and Differentiation

In recent years, extensive research efforts have been directed toward pluripotent stem cells, primarily due to their remarkable capacity for pluripotency. This unique attribute empowers these cells to undergo self-renewal and differentiate into various cell types originating from the ectoderm, mesoderm, and endoderm germ layers. The delicate balance and precise regulation of self-renewal and differentiation are essential for the survival and functionality of these cells. Notably, exposure to specific environmental stressors can activate numerous transcription factors, initiating a diverse array of stress response pathways. These pathways play pivotal roles in regulating gene expression and protein synthesis, ultimately aiming to preserve cell survival and maintain cellular functions. Reactive oxygen species, heat shock, hypoxia, osmotic stress, DNA damage, endoplasmic reticulum stress, and mechanical stress are among the examples of such stressors. In this review, we comprehensively discuss the impact of environmental stressors on the growth of embryonic cells. Furthermore, we provide a summary of the distinct stress response pathways triggered when pluripotent stem cells are exposed to different environmental stressors. Additionally, we highlight recent discoveries regarding the role of such stressors in the generation, differentiation, and self-renewal of induced pluripotent stem cells.

Molecular Chaperones' Potential against Defective Proteostasis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neuronal degenerative condition identified via a build-up of mutant aberrantly folded proteins. The native folding of polypeptides is mediated by molecular chaperones, preventing their pathogenic aggregation. The mutant protein expression in ALS is linked with the entrapment and depletion of chaperone capacity. The lack of a thorough understanding of chaperones' involvement in ALS pathogenesis presents a significant challenge in its treatment. Here, we review how the accumulation of the ALS-linked mutant FUS, TDP-43, SOD1, and C9orf72 proteins damage cellular homeostasis mechanisms leading to neuronal loss. Further, we discuss how the HSP70 and DNAJ family co-chaperones can act as potential targets for reducing misfolded protein accumulation in ALS. Moreover, small HSPB1 and HSPB8 chaperones can facilitate neuroprotection and prevent stress-associated misfolded protein apoptosis. Designing therapeutic strategies by pharmacologically enhancing cellular chaperone capacity to reduce mutant protein proteotoxic effects on ALS pathomechanisms can be a considerable advancement. Chaperones, apart from directly interacting with misfolded proteins for protein quality control, can also filter their toxicity by initiating strong stress-response pathways, modulating transcriptional expression profiles, and promoting anti-apoptotic functions. Overall, these properties of chaperones make them an attractive target for gaining fundamental insights into misfolded protein disorders and designing more effective therapies against ALS.

MicroRNAs in Age-Related Proteostasis and Stress Responses

Aging is associated with the accumulation of damaged and misfolded proteins through a decline in the protein homeostasis (proteostasis) machinery, leading to various age-associated protein misfolding diseases such as Huntington's or Parkinson's. The efficiency of cellular stress response pathways also weakens with age, further contributing to the failure to maintain proteostasis. MicroRNAs (miRNAs or miRs) are a class of small, non-coding RNAs (ncRNAs) that bind target messenger RNAs at their 3'UTR, resulting in the post-transcriptional repression of gene expression. From the discovery of aging roles for lin-4 in C. elegans, the role of numerous miRNAs in controlling the aging process has been uncovered in different organisms. Recent studies have also shown that miRNAs regulate different components of proteostasis machinery as well as cellular response pathways to proteotoxic stress, some of which are very important during aging or in age-related pathologies. Here, we present a review of these findings, highlighting the role of individual miRNAs in age-associated protein folding and degradation across different organisms. We also broadly summarize the relationships between miRNAs and organelle-specific stress response pathways during aging and in various age-associated diseases.

Potential roles of the endoplasmic reticulum stress pathway in amyotrophic lateral sclerosis

The endoplasmic reticulum (ER) is a major organelle involved in protein quality control and cellular homeostasis. ER stress results from structural and functional dysfunction of the organelle, along with the accumulation of misfolded proteins and changes in calcium homeostasis, it leads to ER stress response pathway such as unfolded protein response (UPR). Neurons are particularly sensitive to the accumulation of misfolded proteins. Thus, the ER stress is involved in neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, prion disease and motor neuron disease (MND). Recently, the complex involvement of ER stress pathways has been demonstrated in experimental models of amyotrophic lateral sclerosis (ALS)/MND using pharmacological and genetic manipulation of the unfolded protein response (UPR), an adaptive response to ER stress. Here, we aim to provide recent evidence demonstrating that the ER stress pathway is an essential pathological mechanism of ALS. In addition, we also provide therapeutic strategies that can help treat diseases by targeting the ER stress pathway.

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. Here, we describe a knock-in mouse model where these two serine residues were replaced by alanine residues and have determined the impact of these mutations on cellular proliferation and drug resistance. Our previous study using this mouse model indicated the susceptibility of the mutant mice to become obese with age due to an increase in basal levels of heat shock proteins (HSPs) and chronic inflammation. Since HSF1 transcriptional activity is increased in many tumor types, this mouse model may be a useful tool for studies related to cellular transformation and cancer.

Role of Heat Shock Proteins in Atrial Fibrillation: From Molecular Mechanisms to Diagnostic and Therapeutic Opportunities

Heat shock proteins (HSPs) are endogenous protective proteins and biomarkers of cell stress response, of which examples are HSP70, HSP60, HSP90, and small HSPs (HSPB). HSPs protect cells and organs, especially the cardiovascular system, against harmful and cytotoxic conditions. More recent attention has focused on the roles of HSPs in the irreversible remodeling of atrial fibrillation (AF), which is the most common arrhythmia in clinical practice and a significant contributor to mortality. In this review, we investigated the relationship between HSPs and atrial remodeling mechanisms in AF. PubMed was searched for studies using the terms "Heat Shock Proteins" and "Atrial Fibrillation" and their relevant abbreviations up to 10 July 2022. The results showed that HSPs have cytoprotective roles in atrial cardiomyocytes during AF by promoting reverse electrical and structural remodeling. Heat shock response (HSR) exhaustion, followed by low levels of HSPs, causes proteostasis derailment in cardiomyocytes, which is the basis of AF. Furthermore, potential implications of HSPs in the management of AF are discussed in detail. HSPs represent reliable biomarkers for predicting and staging AF. HSP inducers may serve as novel therapeutic modalities in postoperative AF. HSP induction, either by geranylgeranylacetone (GGA) or by other compounds presently in development, may therefore be an interesting new approach for upstream therapy for AF, a strategy that aims to prevent AF whilst minimizing the ventricular proarrhythmic risks of traditional anti-arrhythmic agents.

Advances in the study of HSP70 inhibitors to enhance the sensitivity of tumor cells to radiotherapy

The 70 kDa heat shock protein (HSP70) is one of the most conserved proteins and a ubiquitous molecular chaperone that plays a role in the folding, remodeling, and degradation of various proteins to maintain proteostasis. It has been shown that HSP70 is abundantly expressed in cancer and enhances tumor resistance to radiotherapy by inhibiting multiple apoptotic pathways, such as interfering with the cellular senescence program, promoting angiogenesis, and supporting metastasis. Thus, HSP70 provides an effective target for enhancing the effects of radiation therapy in the clinical management of cancer patients. Inhibition of HSP70 enhances the radiation-induced tumor-killing effect and thus improves the efficacy of radiotherapy. This article reviews the sensitivity of Hsp70 and its related inhibitors to radiotherapy of tumor cells.

Multidimensional insights into the repeated electromagnetic field stimulation and biosystems interaction in aging and age-related diseases

We provide a multidimensional sequence of events that describe the electromagnetic field (EMF) stimulation and biological system interaction. We describe this process from the quantum to the molecular, cellular, and organismal levels. We hypothesized that the sequence of events of these interactions starts with the oscillatory effect of the repeated electromagnetic stimulation (REMFS). These oscillations affect the interfacial water of an RNA causing changes at the quantum and molecular levels that release protons by quantum tunneling. Then protonation of RNA produces conformational changes that allow it to bind and activate Heat Shock Transcription Factor 1 (HSF1). Activated HSF1 binds to the DNA expressing chaperones that help regulate autophagy and degradation of abnormal proteins. This action helps to prevent and treat diseases such as Alzheimer's and Parkinson's disease (PD) by increasing clearance of pathologic proteins. This framework is based on multiple mathematical models, computer simulations, biophysical experiments, and cellular and animal studies. Results of the literature review and our research point towards the capacity of REMFS to manipulate various networks altered in aging (Reale et al. PloS one 9, e104973, 2014), including delay of cellular senescence (Perez et al. 2008, Exp Gerontol 43, 307-316) and reduction in levels of amyloid-β peptides (Aβ) (Perez et al. 2021, Sci Rep 11, 621). Results of these experiments using REMFS at low frequencies can be applied to the treatment of patients with age-related diseases. The use of EMF as a non-invasive therapeutic modality for Alzheimer's disease, specifically, holds promise. It is also necessary to consider the complicated and interconnected genetic and epigenetic effects of the REMFS-biological system's interaction while avoiding any possible adverse effects.

Small Heat Shock Proteins in Retinal Diseases

This review summarizes the latest findings on small heat shock proteins (sHsps) in three major retinal diseases: glaucoma, diabetic retinopathy, and age-related macular degeneration. A general description of the structure and major cellular functions of sHsps is provided in the introductory remarks. Their role in specific retinal diseases, highlighting their regulation, role in pathogenesis, and possible use as therapeutics, is discussed.

Quantitative Comparison of HSF1 Activators

The heat shock response (HSR) pathway is a highly conserved rescue mechanism, which protects the cells from harmful insults disturbing the cellular protein homeostasis via expression of chaperones. Furthermore, it was demonstrated to play crucial roles in various diseases like neurodegeneration and cancer. For neurodegenerative diseases, an overexpression of chaperones is a potential therapeutic approach to clear the cells from non-functional protein aggregates. Therefore, activators of the HSR pathway and its master regulator HSF1 are under close observation. There are numerous HSR activators published in the literature using different model systems, experimental designs, and readout assays. The aim of this work was to provide a quantitative comparison of a broad range of published activators using a newly developed HSF responsive dual-luciferase cell line. Contrary to natural target genes, which are regulated by multiple input pathways, the artificial reporter exclusively reacts to HSF activity. In addition, the results were compared to endogenous heat shock protein expression. As a result, great differences in the intensity of pathway activation were observed. In addition, a parallel viability assessment revealed high variability in the specificity of the drugs. Furthermore, the differences seen compared to published data indicate that some activators exhibit tissue-specific differences leading to interesting assumptions about the regulation of HSF1.

Placental miRNAs Targeting Cellular Stress Response Pathways Are Highly Expressed in Non-Hispanic Black People

Non-Hispanic Black (NHB) people have a 2.5-fold higher risk of maternal mortality when compared to non-Hispanic White (NHW) people. Neonates of NHB people are more likely to be born preterm and small for gestational age, which may be driven by structural racism. The placenta is very sensitive to the maternal environment and may play a critical role in the translation of environmental stressors to pregnancy outcomes. Our aim was to assess the placental miRNA expression profile in both NHB and NHW people and the association between differentially expressed miRNAs and pregnancy outcomes. Placentas were collected from 50 NHB and 74 NHW people with a normal singleton pregnancy undergoing elective cesarean section at term prior to the onset of labor. Placental miRNA expression was measured via whole-genome small RNA-sequencing in a subset of 77 placentas. Fifteen miRNAs were more highly expressed in the placentas of NHB people. Several of these miRNAs were associated with cellular stress response pathways, suggesting that they may be responding to environmental stressors. Placental miR-192-5p expression was lower among NHB people and was positively associated with neonatal adiposity, suggesting it may be sensitive to structural racism with potential impacts on fetal growth.

Impact of Heat Shock Proteins in Neurodegeneration: Possible Therapeutical Targets

Human neurodegenerative diseases occur as a result of various factors. Regardless of the variety in the etiology of development, many of these diseases are characterized by the accumulation of pathological, misfolded proteins; hence, such diseases are considered as proteinopathies. While plenty of research study has been conducted in order to identify the pathophysiology of these proteinopathies, there is still a lack of understanding in terms of potential therapeutic targets. Molecular chaperones present the main workforce for cellular protection and stress response. Therefore, considering these functions, molecular chaperones present a promising target for research within the field of conformational diseases that arise from proteinopathies. Since the association between neurodegenerative disorders and their long-term consequences is well documented, the need for the development of new therapeutic strategies becomes even more critical. In this review, we summarized the molecular function of heat shock proteins and recent progress on their role, involvement, and other mechanisms related to neurodegeneration caused by different etiological factors. Based on the relevant scientific data, we will highlight the functional classification of heat shock proteins, regulatin, and their therapeutic potential for neurodegenerative disorders.

Heat Shock Factors in Protein Quality Control and Spermatogenesis

Proper regulation of cellular protein quality control is crucial for cellular health. It appears that the protein quality control machinery is subjected to distinct regulation in different cellular contexts such as in somatic cells and in germ cells. Heat shock factors (HSFs) play critical role in the control of quality of cellular proteins through controlling expression of many genes encoding different proteins including those for inducible protein chaperones. Mammalian cells exert distinct mechanism of cellular functions through maintenance of tissue-specific HSFs. Here, we have discussed different HSFs and their functions including those during spermatogenesis. We have also discussed the different heat shock proteins induced by the HSFs and their activities in those contexts. We have also identified several small molecule activators and inhibitors of HSFs from different sources reported so far.

Effects of dinoflagellate Gymnodinium catenatum on swimming behavior and expression of heat shock protein (hsp) genes in the brine shrimp Artemia franciscana

To understand the effects of the toxic marine dinoflagellate, Gymnodinium catenatum, on the brine shrimp, Artemia franciscana, we examined the acute toxicity and swimming behavior parameters such as swimming speed, swimming distance, and swimming path trajectory with transcriptional regulation of heat shock protein (hsp) genes in response to G. catenatum exposure. Mortality was not observed in response to G. catenatum. In the case of swimming behavior parameters, swimming speed and swimming distance were significantly decreased (P < 0.05) for 5 min at three concentrations (240, 360, and 600 cells/mL) of G. catenatum, whereas no significant change in swimming path trajectory was observed, suggesting that G. catenatum has potential adverse effects on the swimming behavior of A. franciscana. Additionally, the four A. franciscana-hsp genes (hsp26, hsp40, hsp70, and hsp90) were upregulated in response to G. catenatum. In particular, A. franciscana-hsp40 was significantly upregulated in response to 600 cells/mL G. catenatum, suggesting that A. franciscana-hsp genes are highly associated with cellular defense mechanisms and that A. franciscana-hsp40 is a potential biomarker for G. catenatum exposure. Overall, this study improves our understanding of the effects of G. catenatum on the swimming behavior and cellular defense mechanisms of A. franciscana.

Mechanisms and Treatments in Demyelinating CMT

Demyelinating forms of Charcot-Marie-Tooth disease (CMT) are genetically and phenotypically heterogeneous and result from highly diverse biological mechanisms including gain of function (including dominant negative effects) and loss of function. While no definitive treatment is currently available, rapid advances in defining the pathomechanisms of demyelinating CMT have led to promising pre-clinical studies, as well as emerging clinical trials. Especially promising are the recently completed pre-clinical genetic therapy studies in PMP-22, GJB1, and SH3TC2-associated neuropathies, particularly given the success of similar approaches in humans with spinal muscular atrophy and transthyretin familial polyneuropathy. This article focuses on neuropathies related to mutations in PMP-22, MPZ, and GJB1, which together comprise the most common forms of demyelinating CMT, as well as on select rarer forms for which promising treatment targets have been identified. Clinical characteristics and pathomechanisms are reviewed in detail, with emphasis on therapeutically targetable biological pathways. Also discussed are the challenges facing the CMT research community in its efforts to advance the rapidly evolving biological insights to effective clinical trials. These considerations include the limitations of currently available animal models, the need for personalized medicine approaches/allele-specific interventions for select forms of demyelinating CMT, and the increasing demand for optimal clinical outcome assessments and objective biomarkers.

Heat shock factor 1 in brain tumors: a link with transient receptor potential channels TRPV1 and TRPA1

Novel data report a "cross-talk" between Heat-Shock Factor 1 (HSF1) and the transient receptor potential vanilloid 1 cation channel (TRPV1) located in the cell membrane, introducing these channels as possible drug targets for the regulation of HSF1 activation. This study aims to investigate the co-expression of TRPV1 and HSF1 in human brain tumors. Additionally, the expression of the transient receptor potential ankyrin 1 channel (TRPA1), which is co-operated with TRPV1 in a plethora of cells, was studied. Immunohistochemical staining for HSF1, TRPV1 and TRPA1 expression was quantitatively analyzed in paraffin-embedded semi-serial tissue sections from 74 gliomas and 71 meningiomas. mRNA levels of HSF1, TRPV1 and TRPA1 were evaluated using real-time PCR. Although HSF1 was significantly increased compared with TRPV1/TRPA1 (p ≤ 0.001) in both gliomas and meningiomas, high co-expression levels for HSF1, TRPV1 and TRPA1 were found in 62.50% of diffuse fibrillary astrocytomas (WHO, grade II), 37.50% of anaplastic astrocytomas (WHO, grade III), 16.32% of glioblastomas multiforme (WHO, grade IV), and 42.25% of meningiomas (WHO, grade I and II). Correlation analysis revealed a relationship of HSF1 with TRPV1/TRPA1 in diffuse fibrillary astrocytomas (WHO, grade II) and benign meningiomas (WHO, grade I) contrary to glioblastomas multiforme (WHO, grade IV) and high grade meningiomas (WHO, grade II). Importantly, TRPA1 and TRPV1 expression levels were significantly increased in meningiomas compared with astrocytic tumors (p < 0.05). In conclusion, HSF1 and TRPV1/TRPA1 co-expression may be implicated in the pathogenesis of human brain tumors and should be considered for the therapeutic approaches for these tumors.

Mathematical modeling and analysis of the heat shock protein response during thermal stress in fish and HeLa cells

The climate change has the potential to dramatically affect species' thermal physiology and may change the ecology and evolution of species' lineages. In this work, we investigated the transition of dynamics in the heat shock response when the thermal stress approaches the upper thermal limits of species to understand how the climate change may affect the heat shock responses in ectotherms and endotherms. The heat shock protein 70, HSP70, prevents protein denaturation or misfolding under thermal stresses. When thermal stress increases, the number of misfolded proteins increases, which leads to high levels of HSP70 protein. However, when temperatures approach limits of thermal tolerance (i.e., the critical thermal maximum, CTmax, for ectotherms and the superior critical temperature, SCT, for endotherms), levels of HSP70 protein synthesis start to decrease. Thus, we hypothesized that the temperature at the first reduction of HSP abundance indicates the thermal limits of the species. In this work, we provide a mathematical model to investigate the behavior of the heat shock responses related to HSP70 protein. This model captures the dynamics of HSP70 protein and Hsp70 mRNA, in HeLa cells (i.e., representative for endotherms) and multiple species of fishes (i.e., representative for ectotherms) with different acclimation histories. Based on our hypothesis of the relationship between the HSP70 protein level and CTmax/SCT, our model provides three methods to predict the CTmax of fishes with varying acclimation temperature and the SCT of HeLa cells. The CTmax increases as the acclimation temperature increases in fishes, however the CTmax plateaus when the acclimation temperature is higher than 20°C in brook trout, a representative cool water salmonid. Our model also captures the situation that the heat shock reaction in fish is more sensitive to the heat shock temperature than HeLa cells, when the heat shock temperature is lower than the upper thermal tolerance. However, both fish and HeLa cells are sensitive to the heat shock temperature when the temperature reaches the thermal tolerance limits. Additionally, our sensitive analysis result indicates that the status of some components in the heat shock reaction changes when the temperature reaches the thermal tolerance resulting in failure in protein refolding in fish and speeding up the refolding process in HeLa cells. Mathematical analysis is also applied on a simplified mathematical model to investigate the detailed dynamics of the model, such as the steady states of the substrate, Hsp70 mRNA, and HSP70 protein, at different thermal stresses. The comparison between the original model and simplified model shows that the inhibition on HSP70 protein transcription by thermal stresses leads to the reduction in HSP70 protein at extreme temperatures.

A Gene Expression Biomarker Predicts Heat Shock Factor 1 Activation in a Gene Expression Compendium

The United States Environmental Protection Agency (US EPA) recently developed a tiered testing strategy to use advances in high-throughput transcriptomics (HTTr) testing to identify molecular targets of thousands of environmental chemicals that can be linked to adverse outcomes. Here, we describe a method that uses a gene expression biomarker to predict chemical activation of heat shock factor 1 (HSF1), a transcription factor critical for proteome maintenance. The HSF1 biomarker was built from transcript profiles derived from A375 cells exposed to a HSF1-activating heat shock protein (HSP) 90 inhibitor in the presence or absence of HSF1 expression. The resultant 44 identified genes included those that (1) are dependent on HSF1 for regulation, (2) have direct interactions with HSF1 assessed by ChIP-Seq, and (3) are in the molecular chaperone family. To test for accuracy, the biomarker was compared in a pairwise manner to gene lists derived from treatments with known HSF1 activity (HSP and proteasomal inhibitors) using the correlation-based Running Fisher test; the balanced accuracy for prediction was 96%. A microarray compendium consisting of 12,092 microarray comparisons from human cells exposed to 2670 individual chemicals was screened using our approach; 112 and 19 chemicals were identified as putative HSF1 activators or suppressors, respectively, and most appear to be novel modulators. A large percentage of the chemical treatments that induced HSF1 also induced oxidant-activated NRF2 (∼46%). For five compounds or mixtures, we found that NRF2 activation occurred at lower concentrations or at earlier times than HSF1 activation, supporting the concept of a tiered cellular protection system dependent on the level of chemical-induced stress. The approach described here could be used to identify environmentally relevant chemical HSF1 activators in HTTr data sets.

Persistent pesticides: effects of endosulfan at the molecular level on the aquatic invertebrate Chironomus riparius

Although banned in multiple areas, due to its persistence in the environment, endosulfan constitutes a significant environmental concern. In this work, fourth instar Chironomus riparius larvae were exposed at environmentally relevant endosulfan concentrations of 0.1, 1, and 10 μg/L for 24 h to analyze the possible effects of this acaricide on gene expression and enzymatic activity. Transcriptional changes were studied through the implementation of a real-time polymerase chain reaction array with 42 genes related to several metabolic pathways (endocrine system, detoxification response, stress response, DNA reparation, and immune system). Moreover, glutathione-S-transferase (GST), phenoloxidase (PO), and acetylcholinesterase (AChE) activities were assessed. The five pathways were differentially altered by endosulfan exposure with significant changes in the E93, Dis, MAPR, Met, InR, GSTd3, GSTt3, MRP1, hsp70, hsp40, hsp24, ATM, PARP, Proph, and Def genes. Besides, all of the measured enzymatic activities were modified, with increased activity of GST, followed by PO and AChE. In summary, the results reflected the effects provoked in C. riparius at molecular level despite the absence of lethality. These data raise concerns about the strong alteration on different metabolic routes despite the low concentrations used. Therefore, new risk assessment strategies should consider include the effects at the sub-organismal level as endpoints in addition to the classical ecologically relevant parameters (such as survival). This endeavor will facilitate a comprehensive evaluation of toxicants in the environment.

Proteostasis in the Male and Female Germline: A New Outlook on the Maintenance of Reproductive Health

For fully differentiated, long lived cells the maintenance of protein homeostasis (proteostasis) becomes a crucial determinant of cellular function and viability. Neurons are the most well-known example of this phenomenon where the majority of these cells must survive the entire course of life. However, male and female germ cells are also uniquely dependent on the maintenance of proteostasis to achieve successful fertilization. Oocytes, also long-lived cells, are subjected to prolonged periods of arrest and are largely reliant on the translation of stored mRNAs, accumulated during the growth period, to support meiotic maturation and subsequent embryogenesis. Conversely, sperm cells, while relatively ephemeral, are completely reliant on proteostasis due to the absence of both transcription and translation. Despite these remarkable, cell-specific features there has been little focus on understanding protein homeostasis in reproductive cells and how/whether proteostasis is "reset" during embryogenesis. Here, we seek to capture the momentum of this growing field by highlighting novel findings regarding germline proteostasis and how this knowledge can be used to promote reproductive health. In this review we capture proteostasis in the context of both somatic cell and germline aging and discuss the influence of oxidative stress on protein function. In particular, we highlight the contributions of proteostasis changes to oocyte aging and encourage a focus in this area that may complement the extensive analyses of DNA damage and aneuploidy that have long occupied the oocyte aging field. Moreover, we discuss the influence of common non-enzymatic protein modifications on the stability of proteins in the male germline, how these changes affect sperm function, and how they may be prevented to preserve fertility. Through this review we aim to bring to light a new trajectory for our field and highlight the potential to harness the germ cell's natural proteostasis mechanisms to improve reproductive health. This manuscript will be of interest to those in the fields of proteostasis, aging, male and female gamete reproductive biology, embryogenesis, and life course health.

Critical Effects on Akt Signaling in Adult Zebrafish Brain Following Alterations in Light Exposure

Evidence from human and animal studies indicate that disrupted light cycles leads to alterations of the sleep state, poor cognition, and the risk of developing neuroinflammatory and generalized health disorders. Zebrafish exhibit a diurnal circadian rhythm and are an increasingly popular model in studies of neurophysiology and neuropathophysiology. Here, we investigate the effect of alterations in light cycle on the adult zebrafish brain: we measured the effect of altered, unpredictable light exposure in adult zebrafish telencephalon, homologous to mammalian hippocampus, and the optic tectum, a significant visual processing center with extensive telencephalon connections. The expression of heat shock protein-70 (HSP70), an important cell stress mediator, was significantly decreased in optic tectum of adult zebrafish brain following four days of altered light exposure. Further, pSer473-Akt (protein kinase B) was significantly reduced in telencephalon following light cycle alteration, and pSer9-GSK3β (glycogen synthase kinase-3β) was significantly reduced in both the telencephalon and optic tectum of light-altered fish. Animals exposed to five minutes of environmental enrichment showed significant increase in pSer473Akt, which was significantly attenuated by four days of altered light exposure. These data show for the first time that unpredictable light exposure alters HSP70 expression and dysregulates Akt-GSK3β signaling in the adult zebrafish brain.

Andrographolide upregulates protein quality control mechanisms in cell and mouse through upregulation of mTORC1 function

BACKGROUND

Heat shock response (HSR), a component of cellular protein quality control mechanisms, is defective in different neurodegenerative conditions such as Parkinson's disease (PD). Forced upregulation of heat shock factor 1 (HSF1), an HSR master regulator, showed therapeutic promise in PD models. Many of the reported small-molecule HSF1 activators have limited functions. Therefore, identification and understanding the molecular bases of action of new HSF1 activating molecules is necessary.

METHOD

We used a cell-based reporter system to screen Andrographis paniculata leaf extract to isolate andrographolide as an inducer of HSF1 activity. The andrographolide activity was characterized by analyzing its role in different protein quality control mechanisms.

RESULT

We find that besides ameliorating the PD in MPTP-treated mice, andrographolide upregulated different machineries controlled by HSF1 and NRF2 in both cell and mouse brain. Andrographolide achieves these functions through mTORC1 activated via p38 MAPK and ERK pathways. NRF2 activation is reflected in the upregulation of proteasome as well as autophagy pathways. We further show that NRF2 activation is mediated through mTORC1 driven phosphorylation of p62/sequestosome 1. Studies with different cell types suggested that andrographolide-mediated induction of ROS level underlies all these activities in agreement with the upregulation of mTORC1 and NRF2-antioxidant pathway in mice.

CONCLUSION

Andrographolide through upregulating HSF1 activity ameliorates protein aggregation induced cellular toxicity.

GENERAL SIGNIFICANCE

Our results provide a reasonable basis for use of andrographolide in the therapy regimen for the treatment of PD.

AlphaB-crystallin and breast cancer: role and possible therapeutic strategies

AlphaB-crystallin (HSPB5) is one of the most prominent and well-studied members of the small heat shock protein (sHsp) family. To date, it is known that this protein modulates significant cellular processes and therefore, it is not surprising that its deregulation is involved in various human pathologies, including cancer diseases. Despite the pathogenic significance of HSPB5 in cancer and its regulatory mechanism related to aggressiveness is poorly understood, several reports describe the association of breast carcinoma progression with HSPB5, whose expression is also considered an independent predictor of breast cancer metastasis to the brain. Indeed, numerous authors indicate HSPB5 as a new valuable biomarker for clinicopathological parameters and poor prognosis in breast cancer. Considering the cytoprotective, anti-apoptotic, pro-angiogenic, and pro-metastatic properties of the sHsps, it is not surprising that they are considered as promising targets for anticancer treatment, even though, at present, a deeper understanding of their mode of action is needed to allow the development of precise therapeutic interventions. Data on the direct inhibition of different sHsps demonstrate promising results in cancer pathologies; however, specific strategies against HSPB5 have not been considered. This review highlights the most relevant findings on HSPB5 and its role in breast cancer, as well as the possible strategies in using HSPB5 inhibition for therapeutic purposes.

Regulatory effect of heat shock transcription factor-1 gene on heat shock proteins and its transcriptional regulation analysis in small abalone Haliotis diversicolor

Background

The effects of diverse stresses ultimately alter the structures and functions of proteins. As molecular chaperones, heat shock proteins (HSPs) are a group of highly conserved proteins that help in the refolding of misfolded proteins and the elimination of irreversibly damaged proteins. They are mediated by a family of transcription factors called heat shock factors (HSFs). The small abalone Haliotis diversicolor is a species naturally distributed along the southern coast of China. In this study, the expression of HdHSF1 was inhibited by RNAi in hemocytes in order to further elucidate the regulatory roles of HdHSF1 on heat shock responsive genes in abalone. Meanwhile, to understand the transcriptional regulation of the HdHSF1 gene, the 5′-upstream regulatory region of HdHSF1 was characterized, and the relative promoter activity was examined by dual-luciferase reporter gene assay system in HEK293T cell lines.

Results

After the inhibition of the H. diversicolor HSF1 gene (HdHSF1) by dsRNA (double-stranded RNA), the expression of most heat shock related-genes was down-regulated (p < 0.05). It indicated the importance of HdHSF1 in the heat shock response of H. diversicolor. Meanwhile, 5′-flanking region sequence (2633 bp) of the HdHSF1 gene was cloned; it contained a putative core promoter region, TATA box, CAAT box, CpG island, and many transcription elements. In HEK293T cells, the 5′-flanking region sequence can drive expression of the enhanced green fluorescent protein (EGFP), proving its promoter function. Exposure of cells to the high-temperature (39 °C and 42 °C) resulted in the activation of HdHSF1 promoter activity, which may explain why the expression of the HdHSF1 gene participates in heat shock response. Luciferase activity of different recombinant plasmids, which contained different truncated promoter fragments of the HdHSF1 gene in HEK293T cells, revealed the possible active regions of the promoter. To further identify the binding site of the critical transcription factor in the region, an expression vector with the site-directed mutation was constructed. After being mutated on the GATA-1 binding site, we found that the luciferase activity was significantly increased, which suggested that the GATA-1 binding site has a certain weakening effect on the activity of the HdHSF1 promoter.

Conclusions

These findings suggest that GATA-1 may be one of the transcription factors of HdHSF1, and a possible signaling pathway mediated by HdHSF1 may exist in H. diversicolor to counteract the adverse effects of heat shock stress.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12860-020-00323-9.

Genome-wide identification and structural analysis of heat shock protein gene families in the marine rotifer Brachionus spp.: Potential application in molecular ecotoxicology

Heat shock proteins (Hsp) are class of conserved and ubiquitous stress proteins present in all living organisms from primitive to higher level. Various studies have demonstrated multiple cellular functions of Hsp in living organisms as an important biomarker in response to abiotic and biotic stressors including temperature, salinity, pH, hypoxia, environmental pollutants, and pathogens. However, full understanding on the mechanism and pathway involved in the induction of Hsp still remains challenging, especially in aquatic invertebrates. In this study, the entire Hsp family and subfamily members in the marine rotifers Brachionus spp., one of the cosmopolitan ecotoxicological model organisms, have been genome-widely identified. In Brachionus spp. Hsp family was comprised of Hsp10, small hsp (sHsp), Hsp40, Hsp60, Hsp70/105, and Hsp90, with highest number of genes found within Hsp40 DnaJ homolog subfamily C members. Also, the differences in the orientation of the conserved motifs within Hsp family may have induced differences in transcriptional gene modulation in response to thermal stress in Brachionus koreanus. Overall, Hsp family-specific domains were highly conserved in all three Brachionus spp., relative to Homo sapiens and across other animal taxa and these findings will be helpful for future ecotoxicological studies focusing on Hsps.

Molecular adaptation to calsequestrin 2 (CASQ2) point mutations leading to catecholaminergic polymorphic ventricular tachycardia (CPVT): comparative analysis of R33Q and D307H mutants

Homozygous calsequestrin 2 (CASQ2) point mutations leads to catecholaminergic polymorphic ventricular tachycardia: a common pathogenetic feature appears to be the drastic reduction of mutant CASQ2 in spite of normal transcription. Comparative biochemical analysis of R33Q and D307H knock in mutant mice identifies different pathogenetic mechanisms for CASQ2 degradation and different molecular adaptive mechanisms. In particular, each CASQ2 point mutation evokes specific adaptive cellular and molecular processes in each of the four adaptive pathways investigated. Thus, similar clinical phenotypes and identical cellular mechanism for cardiac arrhythmia might imply different molecular adaptive mechanisms.

HSP90 Inhibition and Modulation of the Proteome: Therapeutical Implications for Idiopathic Pulmonary Fibrosis (IPF)

Idiopathic Pulmonary fibrosis (IPF) is a catastrophic disease with poor outcomes and limited pharmacological approaches. Heat shock protein 90 (HSP90) has been recently involved in the wound-healing pathological response that leads to collagen deposition in patients with IPF and its inhibition represents an exciting drug target against the development of pulmonary fibrosis. Under physiological conditions, HSP90 guarantees proteostasis through the refolding of damaged proteins and the degradation of irreversibly damaged ones. Additionally, its inhibition, by specific HSP90 inhibitors (e.g., 17 AAG, 17 DAG, and AUY-922) has proven beneficial in different preclinical models of human disease. HSP90 inhibition modulates a complex subset of kinases and interferes with intracellular signaling pathways and proteome regulation. In this review, we evaluated the current evidence and rationale for the use of HSP90 inhibitors in the treatment of pulmonary fibrosis, discussed the intracellular pathways involved, described the limitations of the current understanding and provided insights for future research.

Identifying and Characterizing Stress Pathways of Concern for Consumer Safety in Next-Generation Risk Assessment

Many substances for which consumer safety risk assessments need to be conducted are not associated with specific toxicity modes of action, but rather exhibit nonspecific toxicity leading to cell stress. In this work, a cellular stress panel is described, consisting of 36 biomarkers representing mitochondrial toxicity, cell stress, and cell health, measured predominantly using high content imaging. To evaluate the panel, data were generated for 13 substances at exposures consistent with typical use-case scenarios. These included some that have been shown to cause adverse effects in a proportion of exposed humans and have a toxicological mode-of-action associated with cellular stress (eg, doxorubicin, troglitazone, and diclofenac), and some that are not associated with adverse effects due to cellular stress at human-relevant exposures (eg, caffeine, niacinamide, and phenoxyethanol). For each substance, concentration response data were generated for each biomarker at 3 timepoints. A Bayesian model was then developed to quantify the evidence for a biological response, and if present, a credibility range for the estimated point of departure (PoD) was determined. PoDs were compared with the plasma Cmax associated with the typical substance exposures, and indicated a clear differentiation between "low" risk and "high" risk chemical exposure scenarios. Developing robust methods to characterize the in vitro bioactivity of xenobiotics is an important part of non-animal safety assessment. The results presented in this work show that the cellular stress panel can be used, together with other new approach methodologies, to identify chemical exposures that are protective of consumer health.

Targeting metabolic syndrome with phytochemicals: Focus on the role of molecular chaperones and hormesis in drug discovery

Adaptive cellular stress response confers stress tolerance against inflammatory and metabolic disorders. In response to metabolic stress, the key mediator of cellular adaptation and tolerance is a class of molecules called the molecular chaperones (MCs). MCs are highly conserved molecules that play critical role in maintaining protein stability and functionality. Hormesis in this context is a unique adaptation mechanism where a low dose of a stressor (which is toxic at high dose) confers a stress-resistant adaptive cellular phenotype. Hormesis can be observed at different level of biological organization at various measurable endpoints. The MCs are believed to play a key role in adaptation during hormesis. Several phytochemicals are known for their hormetic response and are called phytochemical hormetins. The role of phytochemical-mediated hormesis on the adaptive cellular processes is proposed as a potential therapeutic approach to target inflammation associated with metabolic syndrome. However, the screening of phytochemical hormetins would require a paradigm shift in the methods currently used in drug discovery.

Pharmacologic Approaches for Adapting Proteostasis in the Secretory Pathway to Ameliorate Protein Conformational Diseases

Maintenance of the proteome, ensuring the proper locations, proper conformations, appropriate concentrations, etc., is essential to preserve the health of an organism in the face of environmental insults, infectious diseases, and the challenges associated with aging. Maintaining the proteome is even more difficult in the background of inherited mutations that render a given protein and others handled by the same proteostasis machinery misfolding prone and/or aggregation prone. Maintenance of the proteome or maintaining proteostasis requires the orchestration of protein synthesis, folding, trafficking, and degradation by way of highly conserved, interacting, and competitive proteostasis pathways. Each subcellular compartment has a unique proteostasis network compromising common and specialized proteostasis maintenance pathways. Stress-responsive signaling pathways detect the misfolding and/or aggregation of proteins in specific subcellular compartments using stress sensors and respond by generating an active transcription factor. Subsequent transcriptional programs up-regulate proteostasis network capacity (i.e., ability to fold and degrade proteins in that compartment). Stress-responsive signaling pathways can also be linked by way of signaling cascades to nontranscriptional means to reestablish proteostasis (e.g., by translational attenuation). Proteostasis is also strongly influenced by the inherent kinetics and thermodynamics of the folding, misfolding, and aggregation of individual proteins, and these sequence-based attributes in combination with proteostasis network capacity together influence proteostasis. In this review, we will focus on the growing body of evidence that proteostasis deficits leading to human pathology can be reversed by pharmacologic adaptation of proteostasis network capacity through stress-responsive signaling pathway activation. The power of this approach will be exemplified by focusing on the ATF6 arm of the unfolded protein response stress responsive-signaling pathway that regulates proteostasis network capacity of the secretory pathway.

Serotonin signaling by maternal neurons upon stress ensures progeny survival

Germ cells are vulnerable to stress. Therefore, how organisms protect their future progeny from damage in a fluctuating environment is a fundamental question in biology. We show that in Caenorhabditis elegans, serotonin released by maternal neurons during stress ensures the viability and stress resilience of future offspring. Serotonin acts through a signal transduction pathway conserved between C. elegans and mammalian cells to enable the transcription factor HSF1 to alter chromatin in soon-to-be fertilized germ cells by recruiting the histone chaperone FACT, displacing histones, and initiating protective gene expression. Without serotonin release by maternal neurons, FACT is not recruited by HSF1 in germ cells, transcription occurs but is delayed, and progeny of stressed C. elegans mothers fail to complete development. These studies uncover a novel mechanism by which stress sensing by neurons is coupled to transcription response times of germ cells to protect future offspring.

Identification of HSF1 Target Genes Involved in Thermal Stress in the Pacific Oyster Crassostrea gigas by ChIP-seq

The Pacific oyster Crassostrea gigas, a commercially important species inhabiting the intertidal zone, facing enormous temperature fluctuations. Therefore, it is important to identify candidate genes and key regulatory relationships associated with thermal tolerance, which can aid the molecular breeding of oysters. Heat shock transcription factor 1 (HSF1) plays an important role in the thermal stress resistance. However, the regulatory relationship between the expansion of heat shock protein (HSP) HSP 70 and HSF1 is not yet clear in C. gigas. In this study, we analyzed genes regulated by HSF1 in response to heat shock by chromatin immunoprecipitation followed by sequencing (ChIP-seq), determined the expression patterns of target genes by qRT-PCR, and validated the regulatory relationship between one HSP70 and HSF1. We found 916 peaks corresponding to HSF1 binding sites, and these peaks were annotated to the nearest genes. In Gene Ontology analysis, HSF1 target genes were related to signal transduction, energy production, and response to biotic stimulus. Four HSP70 genes, two HSP40 genes, and one small HSP gene exhibited binding to HSF1. One HSP70 with a binding site in the promoter region was validated to be regulated by HSF1 under heat shock. These results provide a basis for future studies aimed at determining the mechanisms underlying thermal tolerance and provide insights into gene regulation in the Pacific oyster.

Ivermectin inhibits HSP27 and potentiates efficacy of oncogene targeting in tumor models

HSP27 is highly expressed in, and supports oncogene addiction of, many cancers. HSP27 phosphorylation is a limiting step for activation of this protein and a target for inhibition, but its highly disordered structure challenges rational structure-guided drug discovery. We performed multistep biochemical, structural, and computational experiments to define a spherical 24-monomer complex composed of 12 HSP27 dimers with a phosphorylation pocket flanked by serine residues between their N-terminal domains. Ivermectin directly binds this pocket to inhibit MAPKAP2-mediated HSP27 phosphorylation and depolymerization, thereby blocking HSP27-regulated survival signaling and client-oncoprotein interactions. Ivermectin potentiated activity of anti-androgen receptor and anti-EGFR drugs in prostate and EGFR/HER2-driven tumor models, respectively, identifying a repurposing approach for cotargeting stress-adaptive responses to overcome resistance to inhibitors of oncogenic pathway signaling.

Proteasome Inhibitors in Cancer Therapy and their Relation to Redox Regulation

Redox homeostasis is important for the maintenance of cell survival. Under physiological conditions, redox system works in a balance and involves activation of many signaling molecules. Regulation of redox balance via signaling molecules is achieved by different pathways and proteasomal system is a key pathway in this process. Importance of proteasomal system on signaling pathways has been investigated for many years. In this direction, many proteasome targeting molecules have been developed. Some of them are already in the clinic for cancer treatment and some are still under investigation to highlight underlying mechanisms. Although there are many studies done, molecular mechanisms of proteasome inhibitors and related signaling pathways need more detailed explanations. This review aims to discuss redox status and proteasomal system related signaling pathways. In addition, cancer therapies targeting proteasomal system and their effects on redox-related pathways have been summarized.

Intracellular Targeting of Heat Shock Proteins in Differentiated Human Neuronal Cells Following Proteotoxic Stress

HSPA6 (Hsp70B') is an inducible member of the Hsp70 (HSPA) family of heat shock proteins that is present in the human genome and not found in mouse and rat. Hence it is lacking in current animal models of neurodegenerative diseases. To advance knowledge of the little studied HSPA6, differentiated human neuronal SH-SY5Y cells were treated with the proteotoxic stress-inducing agent MG132. A robust induction of HSPA6 was apparent which localized to the periphery of MG132-induced protein aggregates in the neuronal cytoplasm. Components of the protein disaggregation/refolding machine that co-operate with Hsp70 also targeted the periphery of cytoplasmic protein aggregates, including DNAJB1 (Hsp40-1), HSPH1 (Hsp105α), and HSPB1 (Hsp27). These data suggest that HSPA6 is involved in the response of human neuronal cells to proteotoxic stress that is a feature of neurodegenerative diseases which have been characterized as protein misfolding disorders. Constitutively expressed HSPA8 (Hsc70) also localized tothe periphery of cytoplasmic protein aggregates following the treatment of differentiated human neuronal cells with MG132. HSPA8 could provide a rapid response to proteotoxic stress in neuronal cells, circumventing the time required to upregulate inducible Hsps.