Stress-inducible regulation of heat shock factor 1 by the deacetylase SIRT1

Augmentation of the heat shock axis during exceptional longevity in Ames dwarf mice

How the heat shock axis, repair pathways, and proteostasis impact the rate of aging is not fully understood. Recent reports indicate that normal aging leads to a 50% change in several regulatory elements of the heat shock axis. Most notably is the age-dependent enhancement of inhibitory signals associated with accumulated heat shock proteins and hyper-acetylation associated with marked attenuation of heat shock factor 1 (HSF1)–DNA binding activity. Because exceptional longevity is associated with increased resistance to stress, this study evaluated regulatory check points of the heat shock axis in liver extracts from 12 months and 24 months long-lived Ames dwarf mice and compared these findings with aging wild-type mice. This analysis showed that 12M dwarf and wild-type mice have comparable stress responses, whereas old dwarf mice, unlike old wild-type mice, preserve and enhance activating elements of the heat shock axis. Old dwarf mice thwart negative regulation of the heat shock axis typically observed in usual aging such as noted in HSF1 phosphorylation at Ser307 residue, acetylation within its DNA binding domain, and reduction in proteins that attenuate HSF1–DNA binding. Unlike usual aging, dwarf HSF1 protein and mRNA levels increase with age and further enhance by stress. Together these observations suggest that exceptional longevity is associated with compensatory and enhanced HSF1 regulation as an adaptation to age-dependent forces that otherwise downregulate the heat shock axis.

Sirtuin 1 and Skin: Implications in Intrinsic and Extrinsic Aging-A Systematic Review

Skin, as the outermost organ of the body, is constantly exposed to both intrinsic and extrinsic causative factors of aging. Intrinsic aging is related to compromised cellular proliferative capacity, and may be accelerated by harmful environmental influences with the greatest significance of ultraviolet radiation exposure, contributing not only to premature aging, but also to skin carcinogenesis. The overall skin cancer burden and steadily increasing global antiaging market provide an incentive for searching novel targets to improve skin resistance against external injury. Sirtuin 1, initially linked to extension of yeast and rodent lifespan, plays a key role in epigenetic modification of proteins, histones, and chromatin by which regulates the expression of genes implicated in the oxidative stress response and apoptosis. The spectrum of cellular pathways regulated by sirtuin 1 suggests its beneficial impact on skin aging. However, the data on its role in carcinogenesis remains controversial. The aim of this review was to discuss the relevance of sirtuin 1 in skin aging, in the context of intrinsic factors, related to genetic premature aging syndromes, as well as extrinsic modifiable ones, with the assessment of its future application. PubMed were searched from inception to 4 January 2021 for relevant papers with further search carried out on ClinicalTrials.gov. The systematic review included 46 eligible original articles. The evidence from numerous studies proves sirtuin 1 significance in both chronological and premature aging as well as its dual role in cancer development. Several botanical compounds hold the potential to improve skin aging symptoms.

Molecular Chaperones in Osteosarcoma: Diagnosis and Therapeutic Issues

Osteosarcoma (OS) is the most common form of primary bone tumor affecting mainly children and young adults. Despite therapeutic progress, the 5-year survival rate is 70%, but it drops drastically to 30% for poor responders to therapies or for patients with metastases. Identifying new therapeutic targets is thus essential. Heat Shock Proteins (HSPs) are the main effectors of Heat Shock Response (HSR), the expression of which is induced by stressors. HSPs are a large family of proteins involved in the folding and maturation of other proteins in order to maintain proteostasis. HSP overexpression is observed in many cancers, including breast, prostate, colorectal, lung, and ovarian, as well as OS. In this article we reviewed the significant role played by HSPs in molecular mechanisms leading to OS development and progression. HSPs are directly involved in OS cell proliferation, apoptosis inhibition, migration, and drug resistance. We focused on HSP27, HSP60, HSP70 and HSP90 and summarized their potential clinical uses in OS as either biomarkers for diagnosis or therapeutic targets. Finally, based on different types of cancer, we consider the advantage of targeting heat shock factor 1 (HSF1), the major transcriptional regulator of HSPs in OS.

Schizandrin A exhibits potent anticancer activity in colorectal cancer cells by inhibiting heat shock factor 1

Heat shock factor 1 (HSF1) is a powerful multifaceted oncogenic modifier that plays a role in maintaining the protein balance of cancer cells under various stresses. In recent studies, there have been reports of increased expression of HSF1 in colorectal cancer (CRC) cells, and the depletion of the HSF1 gene knockdown has inhibited colon cancer growth both in vivo and in vitro. Therefore, HSF1 is a promising target for colon cancer treatment and chemoprevention. In the present study, we found that Schizandrin A (Sch A) significantly inhibited the growth of CRC cell lines by inducing cell cycle arrest, apoptosis and death. Through HSE luciferase reporter assay and quantitative PCR (qPCR), we identified Sch A as a novel HSF1 inhibitor. In addition, Sch A could effectively inhibit the induction of HSF1 target proteins such as heat-shock protein (HSP) 70 (HSP70) and HSP27, whether in heat shock or normal temperature culture. In the Surface Plasmon Resonance (SPR) experiment, Sch A showed moderate affinity with HSF1, further confirming that Sch A might be a direct HSF1 inhibitor. The molecular docking and molecular dynamic simulation results of HSF1/Sch A suggested that Sch A formed key hydrogen bond and hydrophobic interactions with HSF1, which may contribute to its potent HSF1 inhibition. These findings provide clues for the design of novel HSF1 inhibitors and drug candidates for colon cancer treatment.

Potential roles of natural products in the targeting of proteinopathic neurodegenerative diseases

Defective proteostasis is associated with the gradual accumulations of misfolded proteins and is a hallmark of many age-associated neurodegenerative diseases. In the aged brain, maintenance of the proteostasis network presents a substantial challenge, and its loss contributes to the onset and progression of neurological diseases associated with cognitive decline due to the generation of toxic protein aggregates, a process termed 'proteinopathy'. Emerging evidence suggests that reversing proteinopathies by boosting proteostasis might provide an effective means of preventing neurodegeneration. From this perspective, phytochemicals may play significant roles as potent modulators of the proteostasis network, as previous reports have suggested they can interact with various network components to modify pathologies and confer neuroprotection. This review focuses on some potent phytochemicals that directly or indirectly modulate the proteostasis network and on their possible molecular targets. In addition, we propose strategies for the natural product-based modulation of proteostasis machinery that target proteinopathies.

The Emerging Role of Macrophages in Immune System Dysfunction under Real and Simulated Microgravity Conditions

In the process of exploring space, the astronaut's body undergoes a series of physiological changes. At the level of cellular behavior, microgravity causes significant alterations, including bone loss, muscle atrophy, and cardiovascular deconditioning. At the level of gene expression, microgravity changes the expression of cytokines in many physiological processes, such as cell immunity, proliferation, and differentiation. At the level of signaling pathways, the mitogen-activated protein kinase (MAPK) signaling pathway participates in microgravity-induced immune malfunction. However, the mechanisms of these changes have not been fully elucidated. Recent studies suggest that the malfunction of macrophages is an important breakthrough for immune disorders in microgravity. As the first line of immune defense, macrophages play an essential role in maintaining homeostasis. They activate specific immune responses and participate in large numbers of physiological activities by presenting antigen and secreting cytokines. The purpose of this review is to summarize recent advances on the dysfunction of macrophages arisen from microgravity and to discuss the mechanisms of these abnormal responses. Hopefully, our work will contribute not only to the future exploration on the immune system in space, but also to the development of preventive and therapeutic drugs against the physiological consequences of spaceflight.

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.

Maintenance of protein homeostasis in glia extends lifespan in C. elegans

Mounting evidence support that glia play a key role in organismal ageing. However, the mechanisms by which glia impact ageing are not understood. One of the processes that has significant impact on the rate of ageing is the unfolded protein response. The more robust the UPR, the more the organism can counteract the effect of environmental and genetic stressors. However, how decline of cellular UPR translates into organismal ageing and eventual death is not fully understood. Here we discuss recent findings highlighting that neuropeptides released by glia act long distance to regulate ageing in C. elegans. Taking advantage of the short lifespan and the genetic amenability of this organism, the endoplasmic reticulum unfolded protein responses (UPR^ER) can be activated in C. elegans glia. This leads to cell-nonautonomous activation of the UPR^ER in the intestine. Activation of intestinal UPR^ER requires the function of genes involved in neuropeptide processing and release, suggesting that neuropeptides signal from glia to the intestine to regulate ER stress response. Importantly, the cell-nonautonomous activation of UPR^ER leads to extension of lifespan. Taken together, these data suggest that environmental and genetic factors that impact the response of glia to stress have the potential to influence organismal ageing. Further research on the specific neuropeptides involved should cast new light on the mechanism of ageing and may suggest novel anti-ageing therapies.

Sirtuins and the prevention of immunosenescence

Aging of hematopoietic stem cells (HSCs) has been largely described as one underlying cause of senescence of the immune-hematopoietic system (immunosenescence). A set of well-defined hallmarks characterizes aged HSCs contributing to unbalanced hematopoiesis and aging-associated functional alterations of both branches of the immune system. In this chapter, the contribution of sirtuins, a family of conserved NAD⁺ dependent deacetylases with key roles in metabolism, genome integrity, aging and lifespan, to immunosenescence, will be addressed. In particular, the role of SIRT6 will be deeply analyzed highlighting a multifaceted part of this deacetylase in HSCs aging as well as in the immunosenescence of dendritic cells (DCs). These and other emerging data are currently paving the way for future design and development of rejuvenation means aiming at rescuing age-related changes in immune function in the elderly and combating age-associated hematopoietic diseases.

Heat shock transcription factor 1 is SUMOylated in the activated trimeric state

The heat shock response is a transcriptional program of organisms to counteract an imbalance in protein homeostasis. It is orchestrated in all eukaryotic cells by heat shock transcription factor 1 (Hsf1). Despite very intensive research, the intricacies of the Hsf1 activation-attenuation cycle remain elusive at a molecular level. Post-translational modifications belong to one of the key mechanisms proposed to adapt the Hsf1 activity to the needs of individual cells, and phosphorylation of Hsf1 at multiple sites has attracted much attention. According to cell biological and proteomics data, Hsf1 is also modified by small ubiquitin-like modifier (SUMO) at several sites. How SUMOylation affects Hsf1 activity at a molecular level is still unclear. Here, we analyzed Hsf1 SUMOylation in vitro with purified components to address questions that could not be answered in cell culture models. In vitro Hsf1 is primarily conjugated at lysine 298 with a single SUMO, though we did detect low-level SUMOylation at other sites. Different SUMO E3 ligases such as protein inhibitor of activated STAT 4 enhanced the efficiency of in vitro modification but did not alter SUMO site preferences. We provide evidence that Hsf1 trimerization and phosphorylation at serines 303 and 307 increases SUMOylation efficiency, suggesting that Hsf1 is SUMOylated in its activated state. Hsf1 can be SUMOylated when DNA bound, and SUMOylation of Hsf1 does neither alter DNA-binding affinity nor affects heat shock cognate 71kDa protein (HSPA8)+DnaJ homolog subfamily B member 1-mediated monomerization of Hsf1 trimers and concomitant dislocation from DNA. We propose that SUMOylation acts at the transcription level of the heat shock response.

Telomeres: history, health, and hallmarks of aging

The escalating social and economic burden of an aging world population has placed aging research at center stage. The hallmarks of aging comprise diverse molecular mechanisms and cellular systems that are interrelated and act in concert to drive the aging process. Here, through the lens of telomere biology, we examine how telomere dysfunction may amplify or drive molecular biological processes underlying each hallmark of aging and contribute to development of age-related diseases such as neurodegeneration and cancer. The intimate link of telomeres to aging hallmarks informs preventive and therapeutic interventions designed to attenuate aging itself and reduce the incidence of age-associated diseases.

The aging proteostasis decline: From nematode to human

The aging proteostasis decline manifests in a failure of aging cells and organisms to properly respond to proteotoxic challenges. This proteostasis collapse has long been considered a hallmark of aging in nematodes, and has recently been shown to occur also in human cells upon entry to senescence, opening the way to exploring the phenomenon in the broader context of human aging. Cellular senescence is part of the normal human physiology of aging, with senescent cell accumulation as a prominent feature of aged tissues. Being highly resistant to cell death, senescent cells, as they accumulate, become pro-inflammatory and promote disease. Here we discuss the causes of human senescence proteostasis decline, in view of the current literature on nematodes, on the one hand, and senescence, on the other hand. We review two major aspects of the phenomenon: (1) the decline in transcriptional activation of stress-response pathways, and (2) impairments in proteasome function. We further outline potential underlying mechanisms of transcriptional proteostasis decline, focusing on reduced chromatin dynamics and compromised nuclear integrity. Finally, we discuss potential strategies for reinforcing proteostasis as a means to improve organismal health and address the relationship to senolytics.

Hippocampal insulin resistance and the Sirtuin 1 signaling pathway in diabetes-induced cognitive dysfunction

In the peripheral nervous system, the activation of Sirtuin 1 can improve insulin resistance; however, the role played by Sirtuin 1 in the central nervous system remains unknown. In this study, rat models of diabetes mellitus were generated by a single injection of streptozotocin. At 8 weeks after streptozotocin injection, the Morris water maze test and western blot assays confirmed that the diabetic model rats had learning and memory deficits, insulin resistance, and Sirtuin 1 expression could be detected in the hippocampus. Insulin and the insulin receptor inhibitor S961 were intranasally administered to investigate the regulatory effects of insulin signaling on Sirtuin 1. The results showed that insulin administration improved the impaired cognitive function of diabetic model rats and increased the expression levels of phosphorylated insulin receptor, phosphorylated insulin receptor substrate 1, and Sirtuin 1 in the hippocampus. Conversely, S961 administration resulted in more severe cognitive dysfunction and reduced the expression levels of phosphorylated insulin receptor, phosphorylated insulin receptor substrate 1, and Sirtuin 1. The Sirtuin 1 activator SRT2104 and the inhibitor Sirtinol were injected into the lateral ventricle, which revealed that the activation of Sirtuin 1 increased the expression levels of target of rapamycin complex 1, phosphorylated cAMP-response element-binding protein, and brain-derived neurotrophic factor. Hippocampal dendritic length and spine density also increased in response to Sirtuin 1 activation. In contrast, Sirtinol decreased the expression levels of target of rapamycin complex 1, phosphorylated cAMP-response element-binding protein, and brain-derived neurotrophic factor and damaged the dendritic structure. These findings suggest that the Sirtuin 1 signaling pathway plays an important role in the development of insulin resistance-related cognitive deficits in diabetic rats. This study was approved by the Animal Ethics Welfare Committee of the First Affiliated Hospital of Hunan University of Chinese Medicine (approval No. ZYFY201811207) in November 2018.

Axonal mRNA localization and local translation in neurodegenerative disease

The regulation of mRNA localization and local translation play vital roles in the maintenance of cellular structure and function. Many human neurodegenerative diseases, such as fragile X syndrome, amyotrophic lateral sclerosis, Alzheimer's disease, and spinal muscular atrophy, have been characterized by pathological changes in neuronal axons, including abnormal mRNA translation, the loss of protein expression, or abnormal axon transport. Moreover, the same protein and mRNA molecules have been associated with variable functions in different diseases due to differences in their interaction networks. In this review, we briefly examine fragile X syndrome, amyotrophic lateral sclerosis, Alzheimer's disease, and spinal muscular atrophy, with a focus on disease pathogenesis with regard to local mRNA translation and axon transport, suggesting possible treatment directions.

The role of plant polyphenols in the health preservation: Effects on human cardiometabolic function

Regardless of the continuous improvement of diagnostic possibilities and the organizational structure of the healthcare system that contribute to the reduction of the complicated courses of diseases, modern socio-economic and environmental stressors, life habits and increased fluctuation in the psychological functioning of an individual still have a great influence on the overall burden of human diseases. At present, etiological factors and pathogenic mechanisms of numerous diseases are known, thus enabling their continuous and timely pharmacotherapy. However, for progressive diseases or those associated with numeorus complications, pharmacological treatment can lead to the side effects, and preventive measures are highlighted as the main strategy in the management of such diseases, especially in chronic non-communicable diseases such as cardiovascular diseases (CVDs). One of the preventive measures is timely and qualitative supplementation of the diet with beneficial micronutrients and oligoelements. Their main sources are represented in plant fibers that synthesize biologically active substances with a polyphenolic ring in their structure, called natural polyphenolic compounds (NPC). Decades of NPC research have brought new insights into the potential modification of existing pharmacotherapy of numeorus diseases. Currently, it is known that many polyphenols have an optimal pharmacological profile with cardioprotection and at the center of their overall effects. Research into the mechanisms of polyphenolic action is exhaustive, their interactions with numerous subcellular structures have been described, and they are refered as promising molecules, with the potential to modify key pathogenetic elements that lead to the progression of various diseases. So far, their numerous effects on endothelium, smooth muscle cells and lipid cells involved in the process of atherogenesis are known, their antidiabetic, antioxidant, anti-inflammatory and immunomodulatory properties have been proven, and the synergy with the intestinal microbial populations has recently been known to contribute to their beneficial effects. This paper has the aim to point out the most important mechanisms that NPC use to improve general functionality of the organism by stimulating its defense capacity, prolonging cell life and delaying its overall aging. As the most important cardioprotective nutrients, a special focus is given to their beneficial effects on cardiovascular and metabolic function.

Targeting therapy-resistant prostate cancer via a direct inhibitor of the human heat shock transcription factor 1

Heat shock factor 1 (HSF1) is a cellular stress-protective transcription factor exploited by a wide range of cancers to drive proliferation, survival, invasion, and metastasis. Nuclear HSF1 abundance is a prognostic indicator for cancer severity, therapy resistance, and shortened patient survival. The HSF1 gene was amplified, and nuclear HSF1 abundance was markedly increased in prostate cancers and particularly in neuroendocrine prostate cancer (NEPC), for which there are no available treatment options. Despite genetic validation of HSF1 as a therapeutic target in a range of cancers, a direct and selective small-molecule HSF1 inhibitor has not been validated or developed for use in the clinic. We described the identification of a direct HSF1 inhibitor, Direct Targeted HSF1 InhiBitor (DTHIB), which physically engages HSF1 and selectively stimulates degradation of nuclear HSF1. DTHIB robustly inhibited the HSF1 cancer gene signature and prostate cancer cell proliferation. In addition, it potently attenuated tumor progression in four therapy-resistant prostate cancer animal models, including an NEPC model, where it caused profound tumor regression. This study reports the identification and validation of a direct HSF1 inhibitor and provides a path for the development of a small-molecule HSF1-targeted therapy for prostate cancers and other therapy-resistant cancers.

Elucidating the Neuroprotective Role of Formulated Camel α-Lactalbumin-Oleic Acid Complex by Curating the SIRT1 Pathway in Parkinson's Disease Model

Parkinson's Disease (PD) is characterized by increased oxidative stress and decreased level of dopamine. At present, the therapeutic interventions of PD are associated with undesirable adverse effects. To overcome these side effects, a new candidate bioinspired molecule is needed for the management of PD. Camel α-lactalbumin (α-LA) is the most abundant protein in camel's milk and has a potential to act as a nutraceutical supplement for neurological functions. Oleic acid, a monounsaturated fatty acid, has been widely associated with a reduced risk of PD. The present study aimed to formulate the camel α-LA and oleic acid (CLOA) complex under specific conditions and to evaluate its efficacy as a neuroprotective in rotenone induced PC12 cell model of PD. Our results demonstrated that removal of Ca++ ions from camel α-LA by EDTA enhances its binding efficiency with oleic acid, and the complex was characterized by UV-CD, ANS fluorescence spectroscopy, and NMR spectroscopy. Moreover, CLOA complex treatment reduced the oxidative stress and increased the cell viability by enhancing the level of dopamine and the expression of SIRT1, FOXO3a, HIF-1α, and HSF-1. We also validated the neuroprotective role of the complex by incubating the cells with CLOA complex prior to rotenone treatment. We inferred from the outcome of the results that the individual entity, i.e., α-LA or OA, is not as effective as the complex. Taken together, our study indicates that CLOA complex might be a potential candidate for the development of future therapeutic drugs for PD.

Sirtuin3 in Neurological Disorders

Sirtuins are NAD+ dependent enzymes that have a predominant role in neurodegenerative disorders and also regulate the inflammatory process, protein aggregation, etc. The relation between Sirtuins with that of the nervous system and neurodegeneration are widely studied consequently. Sirtuins have a strong role in metabolic syndrome in mitochondria also. The activities of Sirtuins can be altered by using small molecules that would be developed into drugs and it is proven that manipulation of SIRT1 activity influences neurodegenerative disease models. They are especially thrilling since using small molecules, which would be developed into a drug, it is feasible to alter the activities of sirtuins. Different functions of Sirtuins are depended upon their subcellular localization. In this review paper, we are discussing different Sirtuins, differential expression of sirtuins, and expression of sirtuin in the brain and briefly about sirtuin3 (SIRT3).

The Critical Role of SIRT1 in Parkinson's Disease: Mechanism and Therapeutic Considerations

Silence information regulator 1 (SIRT1), a member of the sirtuin family, targets histones and many non-histone proteins and participates in various physiological functions. The enzymatic activity of SIRT1 is decreased in patients with Parkinson’s disease (PD), which may reduce their ability to resist neuronal damage caused by various neurotoxins. As far as we know, SIRT1 can induce autophagy by regulating autophagy related proteins such as AMP-activated protein kinase, light chain 3, mammalian target of rapamycin, and forkhead transcription factor 1. Furthermore, SIRT1 can regulate mitochondrial function and inhibit oxidative stress mainly by maintaining peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in a deacetylated state and thus maintaining a constant level of PGC-1α. Other studies have demonstrated that SIRT1 may play a role in the pathophysiology of PD by regulating neuroinflammation. SIRT1 deacetylases nuclear factor-kappa B and thus reduces its transcriptional activity, inhibits inducible nitric oxide synthase expression, and decreases tumor necrosis factor-alpha and interleukin-6 levels. SIRT1 can also upregulate heat shock protein 70 by deacetylating heat shock factor 1 to increase the degradation of α-synuclein oligomers. Few studies have focused on the relationship between SIRT1 single nucleotide polymorphisms and PD risk, so this topic requires further research. Based on the neuroprotective effects of SIRT1 on PD, many in vitro and in vivo experiments have demonstrated that some SIRT1 activators, notably resveratrol, have potential neuroprotective effects against dopaminergic neuronal damage caused by various neurotoxins. Thus, SIRT1 plays a critical role in PD development and might be a potential target for PD therapy.

Cellular proteostasis decline in human senescence

Protein homeostasis (proteostasis), the balance between protein synthesis, folding, and degradation, is thought to deteriorate with age, and the prevalence of protein misfolding diseases (e.g., Alzheimer’s, Parkinson’s, etc.) with human aging is increased. However, while in worms this phenomenon has been well established, in humans, it remained unclear. Here, we show that proteostasis is declined in human cellular aging, termed cellular senescence. We found that while stress sensing is enhanced in senescent cells, and their response at the level of protein synthesis is intact, they fail to properly activate multiple programs required for stress adaptation at the level of gene transcription. Our findings support the notion that proteostasis decline may have major implications on human aging.

Proteostasis collapse, the diminished ability to maintain protein homeostasis, has been established as a hallmark of nematode aging. However, whether proteostasis collapse occurs in humans has remained unclear. Here, we demonstrate that proteostasis decline is intrinsic to human senescence. Using transcriptome-wide characterization of gene expression, splicing, and translation, we found a significant deterioration in the transcriptional activation of the heat shock response in stressed senescent cells. Furthermore, phosphorylated HSF1 nuclear localization and distribution were impaired in senescence. Interestingly, alternative splicing regulation was also dampened. Surprisingly, we found a decoupling between different unfolded protein response (UPR) branches in stressed senescent cells. While young cells initiated UPR-related translational and transcriptional regulatory responses, senescent cells showed enhanced translational regulation and endoplasmic reticulum (ER) stress sensing; however, they were unable to trigger UPR-related transcriptional responses. This was accompanied by diminished ATF6 nuclear localization in stressed senescent cells. Finally, we found that proteasome function was impaired following heat stress in senescent cells, and did not recover upon return to normal temperature. Together, our data unraveled a deterioration in the ability to mount dynamic stress transcriptional programs upon human senescence with broad implications on proteostasis control and connected proteostasis decline to human aging.

Alpha lipoic acid attenuates ER stress and improves glucose uptake through DNAJB3 cochaperone

Persistent ER stress, mitochondrial dysfunction and failure of the heat shock response (HSR) are fundamental hallmarks of insulin resistance (IR); one of the early core metabolic aberrations that leads to type 2 diabetes (T2D). The antioxidant α-lipoic acid (ALA) has been shown to attenuate metabolic stress and improve insulin sensitivity in part through activation of the heat shock response (HSR). However, these studies have been focused on a subset of heat shock proteins (HSPs). In the current investigation, we assessed whether ALA has an effect on modulating the expression of DNAJB3/HSP40 cochaperone; a potential therapeutic target with a novel role in mitigating metabolic stress and promoting insulin signaling. Treatment of C2C12 cells with 0.3 mM of ALA triggers a significant increase in the expression of DNAJB3 mRNA and protein. A similar increase in DNAJB3 mRNA was also observed in HepG2 cells. We next investigated the significance of such activation on endoplasmic reticulum (ER) stress and glucose uptake. ALA pre-treatment significantly reduced the expression of ER stress markers namely, GRP78, XBP1, sXBP1 and ATF4 in response to tunicamycin. In functional assays, ALA treatment abrogated significantly the tunicamycin-mediated transcriptional activation of ATF6 while it enhanced the insulin-stimulated glucose uptake and Glut4 translocation. Silencing the expression of DNAJB3 but not HSP72 abolished the protective effect of ALA on tunicamycin-induced ER stress, suggesting thus that DNAJB3 is a key mediator of ALA-alleviated tunicamycin-induced ER stress. Furthermore, the effect of ALA on insulin-stimulated glucose uptake is significantly reduced in C2C12 and HepG2 cells transfected with DNAJB3 siRNA. In summary, our results are supportive of an essential role of DNAJB3 as a molecular target through which ALA alleviates ER stress and improves glucose uptake.

Mechanisms of Aging and the Preventive Effects of Resveratrol on Age-Related Diseases

Aging gradually decreases cellular biological functions and increases the risk of age-related diseases. Cancer, type 2 diabetes mellitus, cardiovascular disease, and neurological disorders are commonly classified as age-related diseases that can affect the lifespan and health of individuals. Aging is a complicated and sophisticated biological process involving damage to biochemical macromolecules including DNA, proteins, and cellular organelles such as mitochondria. Aging causes multiple alterations in biological processes including energy metabolism and nutrient sensing, thus reducing cell proliferation and causing cellular senescence. Among the polyphenolic phytochemicals, resveratrol is believed to reduce the negative effects of the aging process through its multiple biological activities. Resveratrol increases the lifespan of several model organisms by regulating oxidative stress, energy metabolism, nutrient sensing, and epigenetics, primarily by activating sirtuin 1. This review summarizes the most important biological mechanisms of aging, and the ability of resveratrol to prevent age-related diseases.

Low density lipoprotein receptor related protein 6 (LRP6) protects heart against oxidative stress by the crosstalk of HSF1 and GSK3β

Low density lipoprotein receptor-related protein 6 (LRP6), a Wnt co-receptor, induces multiple functions in various organs. We recently reported cardiac specific LRP6 deficiency caused cardiac dysfunction in mice. Whether cardiomyocyte-expressed LRP6 protects hearts against ischemic stress is largely unknown. Here, we investigated the effects of cardiac LRP6 in response to ischemic reperfusion (I/R) injury. Tamoxifen inducible cardiac specific LRP6 overexpression mice were generated to build I/R model by occlusion of the left anterior descending (LAD) coronary artery for 40 min and subsequent release of specific time. Cardiac specific LRP6 overexpression significantly ameliorated myocardial I/R injury as characterized by the improved cardiac function, strain pattern and infarct area at 24 h after reperfusion. I/R induced-apoptosis and endoplasmic reticulum (ER) stress were greatly inhibited by LRP6 overexpression in cardiomyocytes. LRP6 overexpression enhanced the expression of heat shock transcription factor-1(HSF1) and heat shock proteins (HSPs), the level of p-glycogen synthase kinase 3β(GSK3β)(S9) and p-AMPK under I/R. HSF1 inhibitor deteriorated the apoptosis and decreased p-GSK3β(S9) level in LRP6 overexpressed -cardiomyocytes treated with H2O2. Si-HSF1 or overexpression of active GSK3β significantly attenuated the increased expression of HSF1 and p-AMPK, and the inhibition of apoptosis and ER stress induced by LRP6 overexpression in H2O2-treated cardiomyocytes. AMPK inhibitor suppressed the increase in p-GSK3β (S9) level but didn't alter HSF1 nucleus expression in LRP6 overexpressed-cardiomyocytes treated with H2O2. Active GSK3β, but not AMPK inhibitor, attenuated the inhibition of ubiquitination of HSF1 induced by LRP6-overexpressed-cardiomyocytes treated with H2O2. LRP6 overexpression increased interaction of HSF1 and GSK3β which may be involved in the reciprocal regulation under oxidative stress. In conclusion, cardiac LRP6 overexpression significantly inhibits cardiomyocyte apoptosis and ameliorates myocardial I/R injury by the crosstalk of HSF1 and GSK3β signaling.

Enterotoxigenic Escherichia coli infection promotes enteric defensin expression via FOXO6-METTL3-m6A-GPR161 signalling axis

The production of natural antimicrobial peptides has emerged as an important mechanism of innate immunity in animals. Defensins, members of a large family of antimicrobial peptides, have been suggested as effector molecules in host defence against bacteria, fungi, protozoa and enveloped viruses. However, the molecular mechanism underlying defensin upregulation in bacterial infection remains poorly understood. The modification of mRNA by N6-adenosine methylation (m⁶A) on internal bases influences gene expression in eukaryotes. Here, we show that β-defensin production triggered by Enterotoxigenic Escherichia coli K88 (E. coli K88) infection is controlled by the cellular m⁶A methyltransferase METTL3. Adding back with METTL3 robustly stimulated the re-expression of defensin, which further supports the conclusion. Furthermore, using a MeRIP-seq approach, we identified a functional connection between m⁶A dependent GPR161 signalling and the expression of defensins. Mechanistically, we found that the transcription factor FOXO6 interacted with METTL3 to trigger the transcription of GPR161 and the subsequent regulation of β-defensin expression. The study has shed light on the mechanisms by which enterotoxigenic Escherichia coli infection promotes enteric defensin expression.

Cerebral Fructose Metabolism as a Potential Mechanism Driving Alzheimer's Disease

The loss of cognitive function in Alzheimer's disease is pathologically linked with neurofibrillary tangles, amyloid deposition, and loss of neuronal communication. Cerebral insulin resistance and mitochondrial dysfunction have emerged as important contributors to pathogenesis supporting our hypothesis that cerebral fructose metabolism is a key initiating pathway for Alzheimer's disease. Fructose is unique among nutrients because it activates a survival pathway to protect animals from starvation by lowering energy in cells in association with adenosine monophosphate degradation to uric acid. The fall in energy from fructose metabolism stimulates foraging and food intake while reducing energy and oxygen needs by decreasing mitochondrial function, stimulating glycolysis, and inducing insulin resistance. When fructose metabolism is overactivated systemically, such as from excessive fructose intake, this can lead to obesity and diabetes. Herein, we present evidence that Alzheimer's disease may be driven by overactivation of cerebral fructose metabolism, in which the source of fructose is largely from endogenous production in the brain. Thus, the reduction in mitochondrial energy production is hampered by neuronal glycolysis that is inadequate, resulting in progressive loss of cerebral energy levels required for neurons to remain functional and viable. In essence, we propose that Alzheimer's disease is a modern disease driven by changes in dietary lifestyle in which fructose can disrupt cerebral metabolism and neuronal function. Inhibition of intracerebral fructose metabolism could provide a novel way to prevent and treat this disease.

RNA aptamer capture of macromolecular complexes for mass spectrometry analysis

Specific genomic functions are dictated by macromolecular complexes (MCs) containing multiple proteins. Affinity purification of these complexes, often using antibodies, followed by mass spectrometry (MS) has revolutionized our ability to identify the composition of MCs. However, conventional immunoprecipitations suffer from contaminating antibody/serum-derived peptides that limit the sensitivity of detection for low-abundant interacting partners using MS. Here, we present AptA-MS (aptamer affinity-mass spectrometry), a robust strategy primarily using a specific, high-affinity RNA aptamer against Green Fluorescent Protein (GFP) to identify interactors of a GFP-tagged protein of interest by high-resolution MS. Utilizing this approach, we have identified the known molecular chaperones that interact with human Heat Shock Factor 1 (HSF1), and observed an increased association with several proteins upon heat shock, including translation elongation factors and histones. HSF1 is known to be regulated by multiple post-translational modifications (PTMs), and we observe both known and new sites of modifications on HSF1. We show that AptA-MS provides a dramatic target enrichment and detection sensitivity in evolutionarily diverse organisms and allows identification of PTMs without the need for modification-specific enrichments. In combination with the expanding libraries of GFP-tagged cell lines, this strategy offers a general, inexpensive, and high-resolution alternative to conventional approaches for studying MCs.

Redefining proteostasis transcription factors in organismal stress responses, development, metabolism, and health

Eukaryotic organisms have evolved complex and robust cellular stress response pathways to ensure maintenance of proteostasis and survival during fluctuating environmental conditions. Highly conserved stress response pathways can be triggered and coordinated at the cell-autonomous and cell-nonautonomous level by proteostasis transcription factors, including HSF1, SKN-1/NRF2, HIF1, and DAF-16/FOXO that combat proteotoxic stress caused by environmental challenges. While these transcription factors are often associated with a specific stress condition, they also direct “noncanonical” transcriptional programs that serve to integrate a multitude of physiological responses required for development, metabolism, and defense responses to pathogen infections. In this review, we outline the established function of these key proteostasis transcription factors at the cell-autonomous and cell-nonautonomous level and discuss a newly emerging stress responsive transcription factor, PQM-1, within the proteostasis network. We look beyond the canonical stress response roles of proteostasis transcription factors and highlight their function in integrating different physiological stimuli to maintain cytosolic organismal proteostasis.

Hsf1 on a leash - controlling the heat shock response by chaperone titration

Heat shock factor 1 (Hsf1) is an ancient transcription factor that monitors protein homeostasis (proteostasis) and counteracts disturbances by triggering a transcriptional programme known as the heat shock response (HSR). The HSR is transiently activated and upregulates the expression of core proteostasis genes, including chaperones. Dysregulation of Hsf1 and its target genes are associated with disease; cancer cells rely on a constitutively active Hsf1 to promote rapid growth and malignancy, whereas Hsf1 hypoactivation in neurodegenerative disorders results in formation of toxic aggregates. These central but opposing roles highlight the importance of understanding the underlying molecular mechanisms that control Hsf1 activity. According to current understanding, Hsf1 is maintained latent by chaperone interactions but proteostasis perturbations titrate chaperone availability as a result of chaperone sequestration by misfolded proteins. Liberated and activated Hsf1 triggers a negative feedback loop by inducing the expression of key chaperones. Until recently, Hsp90 has been highlighted as the central negative regulator of Hsf1 activity. In this review, we focus on recent advances regarding how the Hsp70 chaperone controls Hsf1 activity and in addition summarise several additional layers of activity control.

Mitochondrial Respiratory Chain and Its Regulatory Elements SIRT1 and SIRT3 Play Important Role in the Initial Process of Energy Conversion after Moxibustion at Local Skin

Objectives

To study how thermal energy is converted after moxibustion at local skin from the view of mitochondrial respiratory chain and its key regulatory elements of sirtuins 1 (SIRT1) and sirtuins 3 (SIRT3).

Methods

Two moxibustion temperatures usually used in clinical practice (38°C and 46°C) were applied to Zusanli (ST36) acupoint for 30 minutes in C57BL/6J mice. Local skin samples were harvested at 30 min and 72 h after moxibustion intervention, respectively. The activity of mitochondrial respiratory chain complexes I–V was detected by spectrophotometry. The expression of SIRT1 and SIRT3 protein was detected by immunofluorescence staining or western blot.

Results

Moxibustion at 38°C triggered more significant increase of mitochondrial respiratory chain complexes I–V expression. However, the protein expression of SIRT1 and SIRT3 at 46°C showed more obvious enhancement. In addition, the effect of mitochondrial respiratory chain complexes I–V activity on local skin of ST36 acupoint was more obvious at 30 min after moxibustion, while the expression of SIRT1 and SIRT3 protein was more significant at 72 h after moxibustion.

Conclusion

Mitochondrial respiratory chain and its key regulatory element proteins SIRT1 and SIRT3 play important role in the initial process of thermal energy conversion stimulated by different moxibustion temperatures in local skin.

Insight into AMPK regulation mechanism in vivo and in vitro: Responses to low temperatures in the olive flounder Paralichthys olivaceus

The olive flounder, Paralichthys olivaceus, is a commercially important maricultured fish in China, Japan, and Korea. Low winter temperatures influence its survival and growth and affect the output of the aquaculture industry. Energy metabolism is essential for fish survival, and the central energy-regulating factor - 5'-AMP-activated protein kinase (AMPK) - plays an important role in responses to cold stress. However, the mechanism of AMPK pathway regulation in fish coping with cold stress remains poorly understood. In the present study, the expression of AMPK and its upstream (LKB1 and CaMKKβ) and downstream genes (SITR1, FOXO1A, and TFAM) in the brain, muscle, and heart was analyzed while the flounder was under cold stress (0.2 ± 0.2 °C). The results showed that low temperatures activated LKB1, CaMKKβ, and AMPK genes in the brain, and the activated AMPK induced expression of SITR1, FOXO1A, and TFAM. In the muscle tissue, the expression patterns of these genes presented a trend of initially decreasing and then increasing, and there was a delay in the response to low temperatures. At the cellular level, comparative analysis of the effects of the activator 5-aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR) and inhibitor compound C of the AMPK pathway demonstrated that cold stress was similar to AICAR, which activated the AMPK pathway with hysteresis. Thus, the regulation mechanism of AMPK under cold stress was preliminarily analyzed. In general, AMPK was involved not only in responses to low temperatures but also in energy regulation under cold stress.

Emerging roles of HSF1 in cancer: Cellular and molecular episodes

Heat shock factor 1 (HSF1) systematically guards proteome stability and proteostasis by regulating the expression of heat shock protein (HSP), thus rendering cancer cells addicted to HSF1. The non-canonical transcriptional programme driven by HSF1, which is distinct from the heat shock response (HSR), plays an indispensable role in the initiation, promotion and progression of cancer. Therefore, HSF1 is widely exploited as a potential therapeutic target in a broad spectrum of cancers. Various molecules and signals in the cell jointly regulate the activation and attenuation of HSF1. The high-level expression of HSF1 in tumours and its relationship with patient prognosis imply that HSF1 can be used as a biomarker for patient prognosis and a target for cancer treatment. In this review, we discuss the newly identified mechanisms of HSF1 activation and regulation, the diverse functions of HSF1 in tumourigenesis, and the feasibility of using HSF1 as a prognostic marker. Disrupting cancer cell proteostasis by targeting HSF1 represents a novel anti-cancer therapeutic strategy.

Regulation of Hsf1 and the Heat Shock Response

The heat shock response (HSR) is characterized by the induction of molecular chaperones following a sudden increase in temperature. In eukaryotes, the HSR comprises the set of genes controlled by the transcription factor Hsf1. The HSR is induced by defects in co-translational protein folding, ribosome biogenesis, organellar targeting of nascent proteins, and protein degradation by the ubiquitin proteasome system. Upon heat shock, these processes may be endogenous sources of polypeptide ligands that activate the HSR. Mechanistically, these ligands are thought to titrate the chaperone Hsp70 away from Hsf1, releasing Hsf1 to induce the full arsenal of cellular chaperones to restore protein homeostasis. In metazoans, this cell-autonomous feedback loop is modulated by the microenvironment and neuronal cues to enable tissue-level and organism-wide coordination.

NAD+ Controls Circadian Reprogramming through PER2 Nuclear Translocation to Counter Aging

Disrupted sleep-wake and molecular circadian rhythms are a feature of aging associated with metabolic disease and reduced levels of NAD+, yet whether changes in nucleotide metabolism control circadian behavioral and genomic rhythms remains unknown. Here, we reveal that supplementation with the NAD+ precursor nicotinamide riboside (NR) markedly reprograms metabolic and stress-response pathways that decline with aging through inhibition of the clock repressor PER2. NR enhances BMAL1 chromatin binding genome-wide through PER2K680 deacetylation, which in turn primes PER2 phosphorylation within a domain that controls nuclear transport and stability and that is mutated in human advanced sleep phase syndrome. In old mice, dampened BMAL1 chromatin binding, transcriptional oscillations, mitochondrial respiration rhythms, and late evening activity are restored by NAD+ repletion to youthful levels with NR. These results reveal effects of NAD+ on metabolism and the circadian system with aging through the spatiotemporal control of the molecular clock.

Feedback regulation of heat shock factor 1 (Hsf1) activity by Hsp70-mediated trimer unzipping and dissociation from DNA

The heat shock response is a universal transcriptional response to proteotoxic stress orchestrated by heat shock transcription factor Hsf1 in all eukaryotic cells. Despite over 40 years of intense research, the mechanism of Hsf1 activity regulation remains poorly understood at the molecular level. In metazoa, Hsf1 trimerizes upon heat shock through a leucine‐zipper domain and binds to DNA. How Hsf1 is dislodged from DNA and monomerized remained enigmatic. Here, using purified proteins, we demonstrate that unmodified trimeric Hsf1 is dissociated from DNA in vitro by Hsc70 and DnaJB1. Hsc70 binds to multiple sites in Hsf1 with different affinities. Hsf1 trimers are monomerized by successive cycles of entropic pulling, unzipping the triple leucine‐zipper. Starting this unzipping at several protomers of the Hsf1 trimer results in faster monomerization. This process directly monitors the concentration of Hsc70 and DnaJB1. During heat shock adaptation, Hsc70 first binds to a high‐affinity site in the transactivation domain, leading to partial attenuation of the response, and subsequently, at higher concentrations, Hsc70 removes Hsf1 from DNA to restore the resting state.

Advances in DNA Repair-Emerging Players in the Arena of Eukaryotic DNA Repair

Genomic DNA is constantly damaged by factors produced during natural metabolic processes as well as agents coming from the external environment. Considering such a wide array of damaging agents, eukaryotic cells have evolved a DNA damage response (DRR) that opposes the influence of deleterious factors. Despite the broad knowledge regarding DNA damage and repair, new areas of research are emerging. New players in the field of DDR are constantly being discovered. The aim of this study is to review current knowledge regarding the roles of sirtuins, heat shock proteins, long-noncoding RNAs and the circadian clock in DDR and distinguish new agents that may have a prominent role in DNA damage response and repair.

Transcription factor YY1 inhibits the expression of THY1 to promote interstitial pulmonary fibrosis by activating the HSF1/miR-214 axis

Interstitial pulmonary fibrosis (IPF) is a progressive disease of diverse etiology manifesting with proliferation of lung fibroblasts and accumulation of extracellular matrix deposition in pulmonary interstitium. Recent studies show aberrant expression of mRNAs and microRNAs (miRNAs) in human embryonic pulmonary fibroblasts (HEPFs). In this study, we investigated effects of the YY1/HSF1/miR-214/THY1 axis on the functions of HEPFs and IPF. Loss- and gain-of-function tests were conducted to identify roles of YY1, HSF1, miR-214, and THY1 in IPF. As determined by RT-qPCR or western blot assay, silencing YY1 down-regulated HSF1 expression and attenuated the expression of pro-proliferative and fibrosis markers in HEPFs. Meanwhile, viability of HEPFs was impeded by YY1 knockdown. The binding relationship between miR-214 and THY1 was verified using dual-luciferase reporter assay. In HEPFs, down-regulation of HSF1 reduced miR-214 expression to repress proliferation and fibrogenic transformation of HEPFs, while inhibition of miR-214 expression could restrain the fibrogenic transformation property of HEPFs by up-regulating THY1. Subsequently, IPF model in mice was induced by bleomycin treatment. These animal experiments validated the protective effects of YY1 knockdown against IPF-induced lung pathological manifestations, which could be reversed by THY1 knockdown. Our study demonstrates the important involvement of YY1/HSF1/miR-214/THY1 axis in the development of IPF.

Molecular Mechanisms of Heat Shock Factors in Cancer

Malignant transformation is accompanied by alterations in the key cellular pathways that regulate development, metabolism, proliferation and motility as well as stress resilience. The members of the transcription factor family, called heat shock factors (HSFs), have been shown to play important roles in all of these biological processes, and in the past decade it has become evident that their activities are rewired during tumorigenesis. This review focuses on the expression patterns and functions of HSF1, HSF2, and HSF4 in specific cancer types, highlighting the mechanisms by which the regulatory functions of these transcription factors are modulated. Recently developed therapeutic approaches that target HSFs are also discussed.

A molecular perspective on age-dependent changes to the heat shock axis

Aging is a complex process associated with progressive damage that leads to cellular dysfunction often accompanied by frailty and age-related diseases. Coping with all types of physiologic stress declines with age. While representing a primordial, cross-species response in poikilo- and homeotherms, the age-dependent perturbation of the stress response is more complex than previously thought. This short review examines how age influences the stress axis at multiple levels that involve both activating and attenuating pathways.

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.

HSF1: Primary Factor in Molecular Chaperone Expression and a Major Contributor to Cancer Morbidity

Heat shock factor 1 (HSF1) is the primary component for initiation of the powerful heat shock response (HSR) in eukaryotes. The HSR is an evolutionarily conserved mechanism for responding to proteotoxic stress and involves the rapid expression of heat shock protein (HSP) molecular chaperones that promote cell viability by facilitating proteostasis. HSF1 activity is amplified in many tumor contexts in a manner that resembles a chronic state of stress, characterized by high levels of HSP gene expression as well as HSF1-mediated non-HSP gene regulation. HSF1 and its gene targets are essential for tumorigenesis across several experimental tumor models, and facilitate metastatic and resistant properties within cancer cells. Recent studies have suggested the significant potential of HSF1 as a therapeutic target and have motivated research efforts to understand the mechanisms of HSF1 regulation and develop methods for pharmacological intervention. We review what is currently known regarding the contribution of HSF1 activity to cancer pathology, its regulation and expression across human cancers, and strategies to target HSF1 for cancer therapy.

Cell-Nonautonomous Regulation of Proteostasis in Aging and Disease

The functional health of the proteome is determined by properties of the proteostasis network (PN) that regulates protein synthesis, folding, macromolecular assembly, translocation, and degradation. In eukaryotes, the PN also integrates protein biogenesis across compartments within the cell and between tissues of metazoans for organismal health and longevity. Additionally, in metazoans, proteome stability and the functional health of proteins is optimized for development and yet declines throughout aging, accelerating the risk for misfolding, aggregation, and cellular dysfunction. Here, I describe the cell-nonautonomous regulation of organismal PN by tissue communication and cell stress-response pathways. These systems are robust from development through reproductive maturity and are genetically programmed to decline abruptly in early adulthood by repression of the heat shock response and other cell-protective stress responses, thus compromising the ability of cells and tissues to properly buffer against the cumulative stress of protein damage during aging. While the failure of multiple protein quality control processes during aging challenges cellular function and tissue health, genetic studies, and the identification of small-molecule proteostasis regulators suggests strategies that can be employed to reset the PN with potential benefit on cellular health and organismal longevity.

SUMOylation and the HSF1-Regulated Chaperone Network Converge to Promote Proteostasis in Response to Heat Shock

The role of stress-induced increases in SUMO2/3 conjugation during the heat shock response (HSR) has remained enigmatic. We investigated SUMO signal transduction at the proteomic and functional level during the HSR in cells depleted of proteostasis network components via chronic heat shock factor 1 inhibition. In the recovery phase post heat shock, high SUMO2/3 conjugation was prolonged in cells lacking sufficient chaperones. Similar results were obtained upon inhibiting HSP90, indicating that increased chaperone activity during the HSR is critical for recovery to normal SUMO2/3 levels post-heat shock. Proteasome inhibition likewise prolonged SUMO2/3 conjugation, indicating that stress-induced SUMO2/3 targets are subsequently degraded by the ubiquitin-proteasome system. Functionally, we suggest that SUMOylation can enhance the solubility of target proteins upon heat shock, a phenomenon that we experimentally observed in vitro. Collectively, our results implicate SUMO2/3 as a rapid response factor that coordinates proteome degradation and assists the maintenance of proteostasis upon proteotoxic stress.

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Chaperone depletion delays recovery of SUMOylation in response to heat shock

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SUMOylated proteins are targeted to the proteasome during heat shock recovery

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Chaperone depletion impairs clearance of Ub/SUMO co-modified proteins after stress

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SUMO is a rapid response factor likely increasing protein solubility under heat shock

Oxidative Stress Dysregulates Protein Homeostasis Within the Male Germ Line

Aims: Oxidative stress is causally linked to male reproductive pathologies, driven primarily by lipid peroxidation and an attendant production of highly reactive lipid aldehydes, such as 4-hydroxynonenal (4HNE) within the male germ line. In somatic cells, 4HNE dysregulates proteostasis via targeting of vulnerable proteins for adduction, causing protein misfolding and eventually aggregation. The aims of this study were to explore whether oxidative stress precipitates an equivalent response in the male germ line and determine the protective mechanisms used by germ cells to prevent this cascade of protein damage. Results: We reveal a causative role for oxidative stress in the accumulation of protein deposits in male germ cells. Specifically, 4HNE treatment resulted in a significant increase in cytosolic protein aggregation within pre- and post-meiotic germ cells as measured by the aggregate-detecting fluorophores ProteoStat and Thioflavin T, and the amyloid-specific anti-A11 and anti-OC antibodies. Our data implicate nucleocytoplasmic transport machinery and molecular chaperones as potential mechanisms for the subcellular compartmentalization and/or suppression of aggregating proteins. Thus, the inhibition of karyopherin transport proteins and molecular chaperones resulted in a significant increase in the accumulation of aggregated cellular protein. Innovation: These data establish the novel paradigm that lipid peroxidation is a key contributor to a decline in proteostasis in developing germ cells. These findings will inform the development of novel strategies to protect germ cells from oxidative stress. Conclusion: Together, these results shed light on proteostasis mechanisms that may assist in the management of misfolded proteins in the male germ line under conditions of acute oxidative stress.

The "HSF connection": Pleiotropic regulation and activities of Heat Shock Factors shape pathophysiological brain development

The Heat Shock Factors (HSFs) have been historically identified as a family of transcription factors that are activated and work in a stress-responsive manner, after exposure to a large variety of stimuli. However, they are also critical in normal conditions, in a life long manner, in a number of physiological processes that encompass gametogenesis, embryonic development and the integrity of adult organs and organisms. The importance of such roles is emphasized by the devastating impact of their deregulation on health, ranging from reproductive failure, neurodevelopmental disorders, cancer, and aging pathologies, including neurodegenerative disorders. Here, we provide an overview of the delicate choreography of the regulation of HSFs during neurodevelopment, at prenatal and postnatal stages. The regulation of HSFs acts at multiple layers and steps, and comprises the control of (i) HSF mRNA and protein levels, (ii) HSF activity in terms of DNA-binding and transcription, (iii) HSF homo- and hetero-oligomerization capacities, and (iv) HSF combinatory set of post-translational modifications. We also describe how these regulatory mechanisms operate in the normal developing brain and how their perturbation impact neurodevelopment under prenatal or perinatal stress conditions. In addition, we put into perspective the possible role of HSFs in the evolution of the vertebrate brains and the importance of the HSF pathway in a large variety of neurodevelopmental disorders.

Chemical Biology Framework to Illuminate Proteostasis

Protein folding in the cell is mediated by an extensive network of >1,000 chaperones, quality control factors, and trafficking mechanisms collectively termed the proteostasis network. While the components and organization of this network are generally well established, our understanding of how protein-folding problems are identified, how the network components integrate to successfully address challenges, and what types of biophysical issues each proteostasis network component is capable of addressing remains immature. We describe a chemical biology-informed framework for studying cellular proteostasis that relies on selection of interesting protein-folding problems and precise researcher control of proteostasis network composition and activities. By combining these methods with multifaceted strategies to monitor protein folding, degradation, trafficking, and aggregation in cells, researchers continue to rapidly generate new insights into cellular proteostasis.

Accurate and Sensitive Quantitation of the Dynamic Heat Shock Proteome Using Tandem Mass Tags

Cells respond to environmental perturbations and insults through modulating protein abundance and function. However, the majority of studies have focused on changes in RNA abundance because quantitative transcriptomics has historically been more facile than quantitative proteomics. Modern Orbitrap mass spectrometers now provide sensitive and deep proteome coverage, allowing direct, global quantification of not only protein abundance but also post-translational modifications (PTMs) that regulate protein activity. We implemented and validated using the well-characterized heat shock response of budding yeast, a tandem mass tagging (TMT), triple-stage mass spectrometry (MS³) strategy to measure global changes in the proteome during the yeast heat shock response over nine time points. We report that basic-pH, ultra-high performance liquid chromatography (UPLC) fractionation of tryptic peptides yields superfractions of minimal redundancy, a crucial requirement for deep coverage and quantification by subsequent LC-MS³. We quantified 2275 proteins across three biological replicates and found that differential expression peaked near 90 min following heat shock (with 868 differentially expressed proteins at 5% false discovery rate). The sensitivity of the approach also allowed us to detect changes in the relative abundance of ubiquitination and phosphorylation PTMs over time. Remarkably, relative quantification of post-translationally modified peptides revealed striking evidence of regulation of the heat shock response by protein PTMs. These data demonstrate that the high precision of TMT-MS³ enables peptide-level quantification of samples, which can reveal important regulation of protein abundance and regulatory PTMs under various experimental conditions.

Effects of osmotic stress on Na+/K+-ATPase, caspase 3/7 activity, and the expression profiling of sirt1, hsf1, and hsp70 in the roughskin sculpin (Trachidermus fasciatus)

Osmoregulation mechanism underlying acclimation of migratory fish to different salinities has been a classical research topic for decades. In this study, the roughskin sculpin (Trachidermus fasciatus) were subjected to two different acute osmotic treatments (one extreme acute and one acute treatment, i.e., E-acute and acute group). Comparisons of branchial enzyme activity, as well as the time-course expression profiling of sirt1, hsf1, and hsp70 were performed to reveal changes at the physiological and molecular levels. As a result, the branchial Na⁺/K⁺-ATPase activity was significantly inhibited and the caspase 3/7 relating to apoptosis was significantly induced in the E-acute group; no significant difference of branchial enzyme activity was detected in the acute group. These results suggested that T. fasciatus could keep stable physiological levels when experiencing the acute salinity change but not under extreme osmotic stress. Significant variations of sirt1, hsf1, and hsp70 expression were determined in the four target tissues (gill, intestine, kidney, and liver). Similar profiling was detected between the time-course expression of sirt1 and hsf1, suggesting their association in the osmoregulation process. Tissue-specific gene expression patterns in all the three target genes showed that each tissue possesses its own gene expression pattern in response to salinity changes. The overall different expression profiling of sirt1, hsf1, and hsp70 under the extreme acute and acute osmotic treatments might respectively represent the molecular regulation of stress response and acclimation. The findings make it possible to provide more reliable data to decipher the mechanism of osmoregulation in migratory fish.

Functions and mechanisms of non-histone protein acetylation

Nε-lysine acetylation was discovered more than half a century ago as a post-translational modification of histones and has been extensively studied in the context of transcription regulation. In the past decade, proteomic analyses have revealed that non-histone proteins are frequently acetylated and constitute a major portion of the acetylome in mammalian cells. Indeed, non-histone protein acetylation is involved in key cellular processes relevant to physiology and disease, such as gene transcription, DNA damage repair, cell division, signal transduction, protein folding, autophagy and metabolism. Acetylation affects protein functions through diverse mechanisms, including by regulating protein stability, enzymatic activity, subcellular localization and crosstalk with other post-translational modifications and by controlling protein-protein and protein-DNA interactions. In this Review, we discuss recent progress in our understanding of the scope, functional diversity and mechanisms of non-histone protein acetylation.