A novel, small molecule inhibitor of Hsc70/Hsp70 potentiates Hsp90 inhibitor induced apoptosis in HCT116 colon carcinoma cells

HSP70 positively regulates translation by interacting with the IRES and stabilizes the viral structural proteins VP1 and VP3 to facilitate duck hepatitis A virus type 1 replication

The maintenance of viral protein homeostasis depends on the interaction between host cell proteins and viral proteins. As a molecular chaperone, heat shock protein 70 (HSP70) has been shown to play an important role in viral infection. Our results showed that HSP70 can affect translation, replication, assembly, and release during the life cycle of duck hepatitis A virus type 1 (DHAV-1). We demonstrated that HSP70 can regulate viral translation by interacting with the DHAV-1 internal ribosome entry site (IRES). In addition, HSP70 interacts with the viral capsid proteins VP1 and VP3 and promotes their stability by inhibiting proteasomal degradation, thereby facilitating the assembly of DHAV-1 virions. This study demonstrates the specific role of HSP70 in regulating DHAV-1 replication, which are helpful for understanding the pathogenesis of DHAV-1 infection and provide additional information about the role of HSP70 in infection by different kinds of picornaviruses, as well as the interaction between picornaviruses and host cells.

Heat Shock Proteins, a Double-Edged Sword: Significance in Cancer Progression, Chemotherapy Resistance and Novel Therapeutic Perspectives

Heat shock proteins (Hsps) are involved in one of the adaptive mechanisms protecting cells against environmental and metabolic stress. Moreover, the large role of these proteins in the carcinogenesis process, as well as in chemoresistance, was noticed. This review aims to draw attention to the possibilities of using Hsps in developing new cancer therapy methods, as well as to indicate directions for future research on this topic. In order to discuss this matter, a thorough review of the latest scientific literature was carried out, taking into account the importance of selected proteins from the Hsp family, including Hsp27, Hsp40, Hsp60, Hsp70, Hsp90 and Hsp110. One of the more characteristic features of all Hsps is that they play a multifaceted role in cancer progression, which makes them an obvious target for modern anticancer therapy. Some researchers emphasize the importance of directly inhibiting the action of these proteins. In turn, others point to their possible use in the design of cancer vaccines, which would work by inducing an immune response in various types of cancer. Due to these possibilities, it is believed that the use of Hsps may contribute to the progress of oncoimmunology, and thus help in the development of modern anticancer therapies, which would be characterized by higher effectiveness and lower toxicity to the patients.

ANXA2 (annexin A2) is crucial to ATG7-mediated autophagy, leading to tumor aggressiveness in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is associated with a poor prognosis and metastatic growth. TNBC cells frequently undergo macroautophagy/autophagy, contributing to tumor progression and chemotherapeutic resistance. ANXA2 (annexin A2), a potential therapeutic target for TNBC, has been reported to stimulate autophagy. In this study, we investigated the role of ANXA2 in autophagic processes in TNBC cells. TNBC patients exhibited high levels of ANXA2, which correlated with poor outcomes. ANXA2 increased LC3B-II levels following bafilomycin A1 treatment and enhanced autophagic flux in TNBC cells. Notably, ANXA2 upregulated the phosphorylation of HSF1 (heat shock transcription factor 1), resulting in the transcriptional activation of ATG7 (autophagy related 7). The mechanistic target of rapamycin kinase complex 2 (MTORC2) played an important role in ANXA2-mediated ATG7 transcription by HSF1. MTORC2 did not affect the mRNA level of ANXA2, but it was involved in the protein stability of ANXA2. HSPA (heat shock protein family A (Hsp70)) was a potential interacting protein with ANXA2, which may protect ANXA2 from lysosomal proteolysis. ANXA2 knockdown significantly increased sensitivity to doxorubicin, the first-line chemotherapeutic regimen for TNBC treatment, suggesting that the inhibition of autophagy by ANXA2 knockdown may overcome doxorubicin resistance. In a TNBC xenograft mouse model, we demonstrated that ANXA2 knockdown combined with doxorubicin administration significantly inhibited tumor growth compared to doxorubicin treatment alone, offering a promising avenue to enhance the effectiveness of chemotherapy. In summary, our study elucidated the molecular mechanism by which ANXA2 modulates autophagy, suggesting a potential therapeutic approach for TNBC treatment.Abbreviation: ATG: autophagy related; ChIP: chromatin-immunoprecipitation; HBSS: Hanks' balanced salt solution; HSF1: heat shock transcription factor 1; MTOR: mechanistic target of rapamycin kinase; TNBC: triple-negative breast cancer; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3.

Combined In-Solution Fragment Screening and Crystallographic Binding-Mode Analysis with a Two-Domain Hsp70 Construct

Heat shock protein 70 (Hsp70) isoforms are key players in the regulation of protein homeostasis and cell death pathways and are therefore attractive targets in cancer research. Developing nucleotide-competitive inhibitors or allosteric modulators, however, has turned out to be very challenging for this protein family, and no Hsp70-directed therapeutics have so far become available. As the field could profit from alternative starting points for inhibitor development, we present the results of a fragment-based screening approach on a two-domain Hsp70 construct using in-solution NMR methods, together with X-ray-crystallographic investigations and mixed-solvent molecular dynamics simulations. The screening protocol resulted in hits on both domains. In particular, fragment binding in a deeply buried pocket at the substrate-binding domain could be detected. The corresponding site is known to be important for communication between the nucleotide-binding and substrate-binding domains of Hsp70 proteins. The main fragment identified at this position also offers an interesting starting point for the development of a dual Hsp70/Hsp90 inhibitor.

The Interplay between Heat Shock Proteins and Cancer Pathogenesis: A Novel Strategy for Cancer Therapeutics

Heat shock proteins (HSPs) are developmentally conserved families of protein found in both prokaryotic and eukaryotic organisms. HSPs are engaged in a diverse range of physiological processes, including molecular chaperone activity to assist the initial protein folding or promote the unfolding and refolding of misfolded intermediates to acquire the normal or native conformation and its translocation and prevent protein aggregation as well as in immunity, apoptosis, and autophagy. These molecular chaperonins are classified into various families according to their molecular size or weight, encompassing small HSPs (e.g., HSP10 and HSP27), HSP40, HSP60, HSP70, HSP90, and the category of large HSPs that include HSP100 and ClpB proteins. The overexpression of HSPs is induced to counteract cell stress at elevated levels in a variety of solid tumors, including anticancer chemotherapy, and is closely related to a worse prognosis and therapeutic resistance to cancer cells. HSPs are also involved in anti-apoptotic properties and are associated with processes of cancer progression and development, such as metastasis, invasion, and cell proliferation. This review outlines the previously mentioned HSPs and their significant involvement in diverse mechanisms of tumor advancement and metastasis, as well as their contribution to identifying potential targets for therapeutic interventions.

Functionalized Nanomaterials for Inhibiting ATP-Dependent Heat Shock Proteins in Cancer Photothermal/Photodynamic Therapy and Combination Therapy

Phototherapies induced by photoactive nanomaterials have inspired and accentuated the importance of nanomedicine in cancer therapy in recent years. During these light-activated cancer therapies, a nanoagent can produce heat and cytotoxic reactive oxygen species by absorption of light energy for photothermal therapy (PTT) and photodynamic therapy (PDT). However, PTT is limited by the self-protective nature of cells, with upregulated production of heat shock proteins (HSP) under mild hyperthermia, which also influences PDT. To reduce HSP production in cancer cells and to enhance PTT/PDT, small HSP inhibitors that can competitively bind at the ATP-binding site of an HSP could be employed. Alternatively, reducing intracellular glucose concentration can also decrease ATP production from the metabolic pathways and downregulate HSP production from glucose deprivation. Other than reversing the thermal resistance of cancer cells for mild-temperature PTT, an HSP inhibitor can also be integrated into functionalized nanomaterials to alleviate tumor hypoxia and enhance the efficacy of PDT. Furthermore, the co-delivery of a small-molecule drug for direct HSP inhibition and a chemotherapeutic drug can integrate enhanced PTT/PDT with chemotherapy (CT). On the other hand, delivering a glucose-deprivation agent like glucose oxidase (GOx) can indirectly inhibit HSP and boost the efficacy of PTT/PDT while combining these therapies with cancer starvation therapy (ST). In this review, we intend to discuss different nanomaterial-based approaches that can inhibit HSP production via ATP regulation and their uses in PTT/PDT and cancer combination therapy such as CT and ST.

HSP90AB1 is a host factor that promotes porcine deltacoronavirus replication

Porcine deltacoronavirus (PDCoV) is an emerging enteropathogenic coronavirus. It causes mortality in neonatal piglets and is of growing concern because of its broad host range, including humans. To date, the mechanism of PDCoV infection remains poorly understood. Here, based on a genome-wide CRISPR screen of PDCoV-infected cells, we found that HSP90AB1 (heat shock protein 90 alpha family class B1) promotes PDCoV infection. Knockdown or KO of HSP90AB1 in LLC-PK cells resulted in a significantly suppressed PDCoV infection. Infected cells treated with HSP90 inhibitors 17-AAG and VER-82576 also showed a significantly suppressed PDCoV infection, although KW-2478, which does not affect the ATPase activity of HSP90AB1, had no effect on PDCoV infection. We found that HSP90AB1 interacts with the N, NS7, and NSP10 proteins of PDCoV. We further evaluated the interaction between N and HSP90AB1 and found that the C-tail domain of the N protein is the HSP90AB1-interacting domain. Further studies showed that HSP90AB1 protects N protein from degradation via the proteasome pathway. In summary, our results reveal a key role for HSP90AB1 in the mechanism of PDCoV infection and contribute to provide new host targets for PDCoV antiviral research.

Targeting HSP70 chaperones by rhein sensitizes liver cancer to artemisinin derivatives

BACKGROUND

Liver cancer is one of common types of cancer with poor prognosis and limited therapies. Heat shock proteins (HSP) are molecular chaperones that have important roles in tumorigenesis, and emerging as therapeutic targets. Artemisinin and rhein are natural agents from Artemisia annua L. and Rheum undulatum L., respectively. Both rhein and artemisinin have anticancer effects; however, the molecular targets of rhein remain to be identified. It is also unclear whether rhein can synergize with artemisinin derivatives to inhibit liver cancer.

PURPOSE

We aim to identify the targets of rhein in the treatment of hepatocarcinoma and determine the effects of combining rhein and artemisinin derivatives on liver cancer cells.

METHODS

The targets of rhein were detected by mass spectrometry and validated by rhein-proteins interaction assays. The effects of rhein on the chaperone activity of HSP72/HSC70/GRP78 were determined by luciferase refolding assays. Cell viability and apoptosis were determined by CCK8 and flow cytometry assays. For in vivo study, xenograft tumor models were established and treated with rhein and artesunate. Tumor growth was monitored regularly.

RESULTS

Mass spectrometry analysis of rhein-binding proteins in HepG2 cells revealed that HSP72, HSC70 and GRP78 were more profoundly pulled down by rhein-crosslinked sepharose 4B beads compared to the control beads. Further experiments demonstrated that rhein directly interacted with HSP72/HSC70/GRP78 proteins, and inhibit their activity of refolding denatured luciferase. Meanwhile, rhein induced proteasomal degradation of HIF1α and β-catenin. Artesunate or dihydroartemisinin in combination with knockdown of both HSP72 and HSC70 significantly inhibited cell viability. The HSP70/HSC70/GRP78 inhibitors VER-155,008 and rhein phenocopied HSP72/HSC70 knockdown, synergizing with artesunate or dihydroartemisinin to inhibit hepatocarcinoma cell viability. Combinatorial treatment with rhein and artemisinin derivatives significantly induced hepatocarcinoma cell apoptosis, and inhibited tumor growth in vivo.

CONCLUSIONS

The current study demonstrates that rhein is a novel HSP72/HSC70/GRP78 inhibitor that suppresses the chaperone activity of HSP70s. Dual inhibition of HSP72 and HSC70 can enhance the sensitivity of hepatocarcinoma cells to artemisinin derivatives. Combined treatment with artemisinin derivative and rhein significantly inhibits hepatocarcinoma. Artemisinin derivatives in combination with dual inhibition of HSP72 and HSC70 represents a new approach to improve cancer therapy.

SPOCK1, as a potential prognostic and therapeutic biomarker for lung adenocarcinoma, is associated with epithelial-mesenchymal transition and immune evasion

BACKGROUND

The occurrence of epithelial-mesenchymal transition (EMT) and immune evasion is considered to contribute to poor prognosis in lung adenocarcinoma (LUAD). Therefore, this study aims to explore the key oncogenes that promote EMT and immune evasion and reveal the expression patterns, prognostic value, and potential biological functions.

METHODS

Firstly, we identified gene modules associated with EMT and Tumor Immune Dysfunction and Exclusion (TIDE) through weighted gene co-expression network analysis (WGCNA). Next, we utilized differential analysis and machine learning to identify the key genes and validate them. Moreover, we analyzed the correlation between key genes and tumor microenvironment remodeling, drug sensitivity, as well as mutation frequency. Furthermore, we explored and validated their malignant biological characteristics through in vitro experiments and clinical samples. Finally, potential drugs for LUAD were screened based on CMap and validated through experiments.

RESULTS

Firstly, WGCNA analysis revealed that red and green modules were highly correlated with EMT and TIDE. Among them, upregulated expression of SPOCK1 was observed in lung adenocarcinoma tissues and was associated with poor prognosis. Additionally, patients in the high SPOCK1 group showed more activation of malignant oncogenic pathways, higher infiltration of immunosuppressive components, and a higher frequency of mutations. The knockdown of SPOCK1 suppressed invasion and metastasis capabilities of lung adenocarcinoma cells, and the high expression of SPOCK1 was associated with low infiltration of CD8+ T cells. Therapeutic aspects, SPOCK1 can be a candidate indicator for drug sensitivity and CMap showed that VER-155008 was the drug candidate with the largest perturbation effect on the SPOCK1 expression profile. In vitro and in vivo experiments validated the cancer-inhibitory effect of VER-155008 in LUAD.

CONCLUSION

This study revealed through comprehensive bioinformatics analysis and experimental analysis that SPOCK1 can promote EMT and immune escape in LUAD, and it may serve as a promising candidate prognostic biomarker and therapeutic target for LUAD.

Human herpesvirus 6A nuclear matrix protein U37 interacts with heat shock transcription factor 1 and activates the heat shock response

Nascent nucleocapsids of herpesviruses acquire a primary envelope during their nuclear export by budding through the inner nuclear membrane into the perinuclear space between the inner and outer nuclear membranes. This process is mediated by a conserved viral heterodimeric complex designated the nuclear egress complex, which consists of the nuclear matrix protein and the nuclear membrane protein. In addition to its essential roles during nuclear egress, the nuclear matrix protein has been shown to interact with intracellular signaling pathway molecules including NF-κB and IFN-β to affect viral or cellular gene expression. The human herpesvirus 6A (HHV-6A) U37 gene encodes a nuclear matrix protein, the role of which has not been analyzed. Here, we show that HHV-6A U37 activates the heat shock element promoter and induces the accumulation of the molecular chaperone Hsp90. Mechanistically, HHV-6A U37 interacts with heat shock transcription factor 1 (HSF1) and induces its phosphorylation at Ser-326. We report that pharmacological inhibition of HSF1, Hsp70, or Hsp90 decreases viral protein accumulation and viral replication. Taken together, our results lead us to propose a model in which HHV-6A U37 activates the heat shock response to support viral gene expression and replication. IMPORTANCE Human herpesvirus 6A (HHV-6A) is a dsDNA virus belonging to the Roseolovirus genus within the Betaherpesvirinae subfamily. It is frequently found in patients with neuroinflammatory disease, although its pathogenetic role, if any, awaits elucidation. The heat shock response is important for cell survival under stressful conditions that disrupt homeostasis. Our results indicate that HHV-6A U37 activates the heat shock element promoter and leads to the accumulation of heat shock proteins. Next, we show that the heat shock response is important for viral replication. Overall, our findings provide new insights into the function of HHV-6A U37 in host cell signaling and identify potential cellular targets involved in HHV-6A pathogenesis and replication.

The multifunction of HSP70 in cancer: Guardian or traitor to the survival of tumor cells and the next potential therapeutic target

Heat shock protein 70 (HSP70) is a highly conserved protein composed of nucleotide-binding domains (NBD) and C-terminal substrate binding domain (SBD) that can function as a "molecular chaperone". HSP70 was discovered to directly or indirectly play a regulatory role in both internal and external apoptosis pathways. Studies have shown that HSP70 can not only promote tumor progression, enhance tumor cell resistance and inhibit anticancer effects but also induce an anticancer response by activating immune cells. In addition, chemotherapy, radiotherapy and immunotherapy for cancer may be affected by HSP70, which has shown promising potential as an anticancer drug. In this review, we summarized the molecular structure and mechanism of HSP70 and discussed the dual effects of HSP70 on tumor cells and the possibility and potential methods of using HSP70 as a target to treat cancer.

Heat shock proteins and cancer: The FoxM1 connection

Heat shock proteins (Hsp) and FoxM1 have significant roles in carcinogenesis. According to their relative molecular weight, Hsps are divided into Hsp110, Hsp90, Hsp70, Hsp60, Hsp40, and small Hsps. Hsp70 can play essential functions in cancer initiation and is overexpressed in several human cancers. Hsp70, in combination with cochaperones HIP and HOP, refolds partially denatured proteins and acts as a cochaperone for Hsp90. Also, Hsp70, in combination with BAG3, regulates the FoxM1 signaling pathway. FoxM1 protein is a transcription factor of the Forkhead family that is overexpressed in most human cancers and is involved in many cancers' development features, including proliferation, migration, invasion, angiogenesis, metastasis, and resistance to apoptosis. This review discusses the Hsp70, Hsp90, and FoxM1 structure and function, the known Hsp70 cochaperones, and Hsp70, Hsp90, and FoxM1 inhibitors.

HSP70 Family in Cancer: Signaling Mechanisms and Therapeutic Advances

The 70 kDa heat shock proteins (HSP70s) are a group of highly conserved and inducible heat shock proteins. One of the main functions of HSP70s is to act as molecular chaperones that are involved in a large variety of cellular protein folding and remodeling processes. HSP70s are found to be over-expressed and may serve as prognostic markers in many types of cancers. HSP70s are also involved in most of the molecular processes of cancer hallmarks as well as the growth and survival of cancer cells. In fact, many effects of HSP70s on cancer cells are not only related to their chaperone activities but rather to their roles in regulating cancer cell signaling. Therefore, a number of drugs directly or indirectly targeting HSP70s, and their co-chaperones have been developed aiming to treat cancer. In this review, we summarized HSP70-related cancer signaling pathways and corresponding key proteins regulated by the family of HSP70s. In addition, we also summarized various treatment approaches and progress of anti-tumor therapy based on targeting HSP70 family proteins.

Reduced Levels of Misfolded and Aggregated Mutant p53 by Proteostatic Activation

In malignant cancer, excessive amounts of mutant p53 often lead to its aggregation, a feature that was recently identified as druggable. Here, we describe that induction of a heat shock-related stress response mediated by Foldlin, a small-molecule tool compound, reduces the protein levels of misfolded/aggregated mutant p53, while contact mutants or wild-type p53 remain largely unaffected. Foldlin also prevented the formation of stress-induced p53 nuclear inclusion bodies. Despite our inability to identify a specific molecular target, Foldlin also reduced protein levels of aggregating SOD1 variants. Finally, by screening a library of 778 FDA-approved compounds for their ability to reduce misfolded mutant p53, we identified the proteasome inhibitor Bortezomib with similar cellular effects as Foldlin. Overall, the induction of a cellular heat shock response seems to be an effective strategy to deal with pathological protein aggregation. It remains to be seen however, how this strategy can be translated to a clinical setting.

A curcumin analogue GO-Y030 depletes cancer stem cells by inhibiting the interaction between the HSP70/HSP40 complex and its substrates

Cancer stem cells (CSCs) are proposed to be involved in tumor initiation and play important roles in cancer relapse, metastasis, and drug resistance. Therefore, the targeting of CSCs has potential for effective anticancer therapies. Curcumin is one of the most widely characterized phytochemicals with tumor-suppressive potential. GO-Y030 is a novel curcumin analogue exhibiting a much stronger growth-inhibitory effect than curcumin. In the present study, we verified the potency of GO-Y030 against a CSC population. We observed that GO-Y030 suppressed CSC sphere-forming ability in several cancer cell lines. Interestingly, a specific inhibitor of heat shock protein (HSP) 70 also exhibited effects similar to GO-Y030 (i.e. inhibition of CSC sphere formation and upregulation of HSP70 and HSP40 protein expression), suggesting that HSP70 and/or HSP40 might be target molecules of GO-Y030. We then performed an in vitro HSP70/HSP40-mediated refolding activity assay and observed that chaperone activity was efficiently inhibited by GO-Y030. Finally, we performed a substrate-binding assay to show that GO-Y030 reduced the binding of both HSP70 and HSP40 with their substrates. HSPs prevent denaturation or unfolding of client proteins under stressful conditions such as high temperature. Because CSCs by nature adapt to various stresses by reinforcing protein-folding activity, the function of HSP70/HSP40 is important for the maintenance of CSC population. Our data suggest that GO-Y030 may impair stress tolerance in CSCs by inhibiting the interaction of HSP70/HSP40 with their substrate proteins and disrupting the function of HSP70/HSP40, thereby contributing to a reduction of the CSC population.

Synthetic Small Molecule Modulators of Hsp70 and Hsp40 Chaperones as Promising Anticancer Agents

A class of chaperones dubbed heat shock protein 70 (Hsp70) possesses high relevance in cancer diseases due to its cooperative activity with the well-established anticancer target Hsp90. However, Hsp70 is closely connected with a smaller heat shock protein, Hsp40, forming a formidable Hsp70-Hsp40 axis in various cancers, which serves as a suitable target for anticancer drug design. This review summarizes the current state and the recent developments in the field of (semi-)synthetic small molecule inhibitors directed against Hsp70 and Hsp40. The medicinal chemistry and anticancer potential of pertinent inhibitors are discussed. Since Hsp90 inhibitors have entered clinical trials but have exhibited severe adverse effects and drug resistance formation, potent Hsp70 and Hsp40 inhibitors may play a significant role in overcoming the drawbacks of Hsp90 inhibitors and other approved anticancer drugs.

HSP70 mediates a crosstalk between the estrogen and the heat shock response pathways

Cells respond to multiple signals from the environment simultaneously, which often creates crosstalk between pathways affecting the capacity to adapt to the changing environment. Chaperones are an important component in the cellular integration of multiple responses to environmental signals, often implicated in negative feedback and inactivation mechanisms. These mechanisms include the stabilization of steroid hormone nuclear receptors in the cytoplasm in the absence of their ligand. Here, we show using immunofluorescence, chromatin immunoprecipitation, and nascent transcripts production that the heat shock protein 70 (HSP70) chaperone plays a central role in a new crosstalk mechanism between the steroid and heat shock response pathways. HSP70-dependent feedback mechanisms are required to inactivate the heat shock factor 1 (HSF1) after activation. Interestingly, a steroid stimulation leads to faster accumulation of HSF1 in inactive foci following heat shock. Our results further show that in the presence of estrogen, HSP70 accumulates at HSF1-regulated noncoding regions, leading to deactivation of HSF1 and the abrogation of the heat shock transcriptional response. Using an HSP70 inhibitor, we demonstrate that the crosstalk between both pathways is dependent on the chaperone activity. These results suggest that HSP70 availability is a key determinant in the transcriptional integration of multiple external signals. Overall, these results offer a better understanding of the crosstalk between the heat shock and steroid responses, which are salient in neurodegenerative disorders and cancers.

Heat Shock Proteins: Central Players in Oncological and Immuno-Oncological Tracks

Heat shock proteins (HSPs) are a group of proteins that promote protein folding, inhibit denaturation of cellular proteins, and maintain other proteins' functional activities when cells are subjected to stress and/or high temperature. HSP classification is generally based on their molecular weights into large and small HSP. The family of small HSPs includes HSPs 27, 40, 60, 70, and 90. The potential roles of HSP27 and HSP70 are quite evident in different solid malignancies, including breast, colorectal, pancreatic, and liver cancers. In this chapter, the authors focus on HSP27 and HSP70 signaling in oncology and their role in different solid malignancies as well as they shed light on the novel role of HSP70 and HSP90 in the immune-oncology field.

The molecular network of the proteasome machinery inhibition response is orchestrated by HSP70, revealing vulnerabilities in cancer cells

Proteasome machinery is a major proteostasis control system in human cells, actively compensated upon its inhibition. To understand this compensation, we compared global protein landscapes upon the proteasome inhibition with carfilzomib, in normal fibroblasts, cells of multiple myeloma, and cancers of lung, colon, and pancreas. Molecular chaperones, autophagy, and endocytosis-related proteins are the most prominent vulnerabilities in combination with carfilzomib, while targeting of the HSP70 family chaperones HSPA1A/B most specifically sensitizes cancer cells to the proteasome inhibition. This suggests a central role of HSP70 in the suppression of the proteasome downregulation, allowing to identify pathways impinging on HSP70 upon the proteasome inhibition. HSPA1A/B indeed controls proteasome-inhibition-induced autophagy, unfolded protein response, and endocytic flux, and directly chaperones the proteasome machinery. However, it does not control the NRF1/2-driven proteasome subunit transcriptional bounce-back. Consequently, targeting of NRF1 proves effective in decreasing the viability of cancer cells with the inhibited proteasome and HSP70.

Heat Shock Protein 70 and 90 Family in Prostate Cancer

Prostate cancer (PCa) is the second most frequent cancer that affects aging men worldwide. However, its exact pathogenesis has not been fully elucidated. The heat shock protein (HSP) family has cell-protective properties that may promote tumor growth and protect cancer cells from death. On a cellular level, HSP molecules have a strong relationship with multiple important biological processes, such as cell differentiation, epithelial-mesenchymal transition (EMT), and fibrosis. Because of the facilitation of HSP family molecules on tumorigenesis, a number of agents and inhibitors are being developed with potent antitumor effects whose target site is the critical structure of HSP molecules. Among all target molecules, HSP70 family and HSP90 are two groups that have been well studied, and therefore, the development of their inhibitors makes great progress. Only a small number of agents, however, have been clinically tested in recruited patients. As a result, more clinical studies are warranted for the establishment of the relationship between the HSP70 family, alongside the HSP90 molecule, and prostate cancer treatment.

Pharmacological agents selectively acting on the channel moieties of TRPM6 and TRPM7

The transient receptor potential cation channel, subfamily M, members 6 and 7 (TRPM6 and TRPM7) are homologous membrane proteins encompassing cation channel units fused to cytosolic serine/threonine-protein kinase domains. Clinical studies and experiments with animal disease models suggested that selective inhibition of TRPM6 and TRPM7 currents might be beneficial for subjects with immune and cardiovascular disorders, tumours and other pathologies, but the suitable pharmacological toolkit remains underdeveloped. The present study identified small synthetic molecules acting specifically on the channel moieties of TRPM6 and TRPM7. Using electrophysiological analysis in conjunction with Ca²⁺ imaging, we show that iloperidone and ifenprodil inhibit the channel activity of recombinant TRPM6 with IC₅₀ values of 0.73 and 3.33 µM, respectively, without an impact on the TRPM7 channel. We also found that VER155008 suppresses the TRPM7 channel with an IC₅₀ value of 0.11 µM but does not affect TRPM6. Finally, the effects of iloperidone and VER155008 were found to be suitable for blocking native endogenous TRPM6 and TRPM7 in a collection of mouse and human cell models. Hence, the identification of iloperidone, ifenprodil, and VER155008 allows for the first time to selectively manipulate TRPM6 and TRPM7 currents.

Age-Related Decline in Vascular Responses to Phenylephrine Is Associated with Reduced Levels of HSP70

Aging impairs the expression of HSP70, an emergent player in vascular biology. However, it is unknown if age-related alterations in HSP70 are linked to a decline in arterial function. In this study, we test the hypothesis that the contributions of HSP70 to vascular contraction are diminished in middle-aged animals. We determined the basal levels of HSP70 in the aorta of young and middle-aged Sprague Dawley male rats using Western blotting. Functional studies were performed in a wire myograph system. Force development in response to phenylephrine was assessed in the presence or absence of extracellular calcium (Ca2+), and in aortic rings treated or non-treated with an HSP70 inhibitor. Fluorescent probes were used to evaluate vascular oxidative stress and nitric oxide levels. We report that middle-aged rats have significantly lower levels of HSP70. Blockade of HSP70 attenuated vascular phasic and tonic contraction in isolated aortas. It appears that a functional HSP70 is required for proper Ca2+ handling as inhibition of this protein led to reduced force-displacement in response to Ca2+ dynamics. Furthermore, middle-aged aortic rings exposed to the HSP70 inhibitor display higher reactive oxygen species levels without changes in nitric oxide. In summary, we show that middle-aged animals have lower levels of HSP70 in aortas, which associates with an age-related decline in vascular responses to α-1 adrenergic stimulation.

The Role of Heat Shock Protein 70 Subfamily in the Hyperplastic Prostate: From Molecular Mechanisms to Therapeutic Opportunities

Benign prostatic hyperplasia (BPH) is one of the most common causes of lower urinary tract symptoms (LUTS) in men, which is characterized by a noncancerous enlargement of the prostate. BPH troubles the vast majority of aging men worldwide; however, the pathogenetic factors of BPH have not been completely identified. The heat shock protein 70 (HSP70) subfamily, which mainly includes HSP70, glucose-regulated protein 78 (GRP78) and GRP75, plays a crucial role in maintaining cellular homeostasis. HSP70s are overexpressed in the course of BPH and involved in a variety of biological processes, such as cell survival and proliferation, cell apoptosis, epithelial/mesenchymal transition (EMT) and fibrosis, contributing to the development and progress of prostate diseases. These chaperone proteins also participate in oxidative stress, a cellular stress response that takes place under stress conditions. In addition, HSP70s can bind to the androgen receptor (AR) and act as a regulator of AR activity. This interaction of HSP70s with AR provides insight into the importance of the HSP70 chaperone family in BPH pathogenesis. In this review, we discuss the function of the HSP70 family in prostate glands and the role of HSP70s in the course of BPH. We also review the potential applications of HSP70s as biomarkers of prostate diseases for targeted therapies.

Combination effects of capecitabine, irinotecan and 17-AAG on colorectal cancer cell line (HT-29)

Objevtive

Evasion of apoptosis is a major feature of cancer cells, therefore designing treatment strategies to target apoptotic pathways seems effective. In this study, we investigate the effect of 17-AAG (17-allylaminogeldanamycin) alone and in double and triple combination with capecitabine (Cap) and irinotecan (IR) on HT-29 colon cancer cell line apoptosis.

Methods

Capase-3, 8, 9, p53 and NF-κB genes expression were analyzed by Real-time PCR. DNA laddering assay was performed to confirm Real-time PCR results.

Results

Our results showed that all single treatment groups elevated expression of caspase-3, 8, and 9 significantly and IR/Cap was the only double combination group that could upregulate caspase-8 and -9. NF-κB was down-regulated in single treatment and IR/Cap double combination group, significantly. 17-AAG mono-treatment and IR/Cap and Cap/17-AAG double combination group significantly upregulated p53 gene expression.

Conclusion

Our findings showed proapoptotic effects of 17-AAG alone and in combination with Cap and IR. These findings propose 17-AAG in combination with routine chemotherapy, as a new protocol for colorectal cancer combination therapy.

•

Targeted therapy of apoptosis is the main effective way against of cancer cells.

•

17-AAG alone and in combination with Cap and IR can regulate the pro-apoptotic factors.

•

Combination therapy has more effective than single therapy.

Cytoplasmic proteotoxicity regulates HRI-dependent phosphorylation of eIF2α via the Hsp70-Bag3 module

The major heat shock protein Hsp70 forms a complex with a scaffold protein Bag3 that links it to components of signaling pathways. Via these interactions, the Hsp70-Bag3 module functions as a proteotoxicity sensor that controls cell signaling. Here, to search for pathways regulated by the complex, we utilized JG-98, an allosteric inhibitor of Hsp70 that blocks its interaction with Bag3. RNAseq followed by the pathway analysis indicated that several signaling pathways including UPR were activated by JG-98. Surprisingly, only the eIF2α-associated branch of the UPR was activated, while other UPR branches were not induced, suggesting that the response was unrelated to the ER proteotoxicity and ER-associated kinase PERK1. Indeed, induction of the UPR genes under these conditions was driven by a distinct eIF2α kinase HRI. Hsp70-Bag3 directly interacted with HRI and regulated eIF2α phosphorylation upon cytoplasmic proteotoxicity. Therefore, cytosolic proteotoxicity can activate certain UPR genes via Hsp70-Bag3-HRI-eIF2α axis.

•

Disruption of Hsp70-Bag3 module activates the unfolded protein response (UPR)

•

This induction of UPR genes is mediated by HRI-dependent phosphorylation of eIF2α

•

Hsp70-Bag3 “monitors” cytoplasmic proteotoxicity to activate the HRI-eIF2α axis

•

eIF2α integrates proteotoxicity signals from ER and cytoplasm

Visualized SERS Imaging of Single Molecule by Ag/Black Phosphorus Nanosheets

Ag/BP-NS exhibit remarkable surface-enhanced Raman scattering performance with single-molecule detection ability. This remarkable enhancement can be attributed to the synergistic resonance enhancement of R6G molecular resonance, photo-induced charge transfer resonance and electromagnetic resonance. A new polarization-mapping method was proposed, which can quickly screen out single-molecule signals and prove that the obtained spectra are emitted by single molecule. The recognition of different tumor exosomes can be realized combining the method of machine learning.

ABSTRACT

Single-molecule detection and imaging are of great value in chemical analysis, biomarker identification and other trace detection fields. However, the localization and visualization of single molecule are still quite a challenge. Here, we report a special-engineered nanostructure of Ag nanoparticles embedded in multi-layer black phosphorus nanosheets (Ag/BP-NS) synthesized by a unique photoreduction method as a surface-enhanced Raman scattering (SERS) sensor. Such a SERS substrate features the lowest detection limit of 10^–20 mol L⁻¹ for R6G, which is due to the three synergistic resonance enhancement of molecular resonance, photo-induced charge transfer resonance and electromagnetic resonance. We propose a polarization-mapping strategy to realize the detection and visualization of single molecule. In addition, combined with machine learning, Ag/BP-NS substrates are capable of recognition of different tumor exosomes, which is meaningful for monitoring and early warning of the cancer. This work provides a reliable strategy for the detection of single molecule and a potential candidate for the practical bio-application of SERS technology. [Image: see text]

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40820-022-00803-x.

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.

Critical Residues in Hsp70 Nucleotide Binding Domain for Challenges in Drug Design

Background:

The association of a drug with its target protein correlates to its medicinal activity and the microenvironment plays a key role in this association. The key challenge is to identify mutations which unlikely to respond to designed drugs.

Objective:

Hsp70 is an anti-apoptotic factor and tumor cells overexpress Hsp70 to survive against anti-cancer agents. The impact of pathogenic mutations on Hsp70 is unknown. Elucidation of these alterations is essential to understand the molecular switch mechanism. Thus, critical spots on Hsp70 Nucleotide Binding Domain (NBD) are important since mutation-driven sensitivity may be useful in designing innovative inhibitors.

Methods:

ATP, AMP-PNP (non-hydrolyzable analog of ATP) along with commercially available compounds VER-155008 (ATP analog and competitive inhibitor) and MKT-077 (allosteric inhibitor of ADP bound form) were docked to Hsp70 NBD structure in silico to identify critical amino acids of inhibition mechanism. Site-directed mutagenesis of the determined critical residues along with ATP hydrolysis and luciferase refolding was performed. Wild-type and mutant Hsp70s were compared to determine the effect on protein functions in the presence or absence of inhibitors.

Results:

This study identified three mutants that have a loss of function for Hsp70, which may alter the drug inhibition activity as oncogenic cells have multiple mutations.

Conclusion:

Two commercial inhibitors employed here that mimic ATP and ADP states, respectively, are not affected by these mutational perturbations and displayed effective interference for Hsp70 functions. Designing inhibitors by considering these critical residues may improve drug design and increase drug efficiency.

The heat shock response and small molecule regulators

The heat shock response (HSR) is a highly conserved cellular pathway that is responsible for stress relief and the refolding of denatured proteins [1]. When a host cell is exposed to conditions such as heat shock, ischemia, or toxic substances, heat shock factor-1 (HSF-1), a transcription factor, activates the genes that encode for the heat shock proteins (Hsps), which are a family of proteins that work alongside other chaperones to relieve stress and refold proteins that have been denatured (Burdon, 1986) [2]. Along with the refolding of denatured proteins, Hsps facilitate the removal of misfolded proteins by escorting them to degradation pathways, thereby preventing the accumulation of misfolded proteins [3]. Research has indicated that many pathological conditions, such as diabetes, cancer, neuropathy, cardiovascular disease, and aging have a negative impact on HSR function and are commonly associated with misfolded protein aggregation [4,5]. Studies indicate an interplay between mitochondrial homeostasis and HSF-1 levels can impact stress resistance, proteostasis, and malignant cell growth, which further support the role of Hsps in pathological and metabolic functions [6]. On the other hand, Hsp activation by specific small molecules can induce the heat shock response, which can afford neuroprotection and other benefits [7]. This review will focus on the modulation of Hsps and the HSR as therapeutic options to treat these conditions.

HSP70s in Breast Cancer: Promoters of Tumorigenesis and Potential Targets/Tools for Therapy

The high frequency of breast cancer worldwide and the high mortality among women with this malignancy are a serious challenge for modern medicine. A deeper understanding of the mechanisms of carcinogenesis and emergence of metastatic, therapy-resistant breast cancers would help development of novel approaches to better treatment of this disease. The review is dedicated to the role of members of the heat shock protein 70 subfamily (HSP70s or HSPA), mainly inducible HSP70, glucose-regulated protein 78 (GRP78 or HSPA5) and GRP75 (HSPA9 or mortalin), in the development and pathogenesis of breast cancer. Various HSP70-mediated cellular mechanisms and pathways which contribute to the oncogenic transformation of mammary gland epithelium are reviewed, as well as their role in the development of human breast carcinomas with invasive, metastatic traits along with the resistance to host immunity and conventional therapeutics. Additionally, intracellular and cell surface HSP70s are considered as potential targets for therapy or sensitization of breast cancer. We also discuss a clinical implication of Hsp70s and approaches to targeting breast cancer with gene vectors or nanoparticles downregulating HSP70s, natural or synthetic (small molecule) inhibitors of HSP70s, HSP70-binding antibodies, HSP70-derived peptides, and HSP70-based vaccines.

Polyamine metabolism links gut microbiota and testicular dysfunction

BACKGROUND

Male fertility impaired by exogenous toxins is a serious worldwide issue threatening the health of the new-born and causing infertility. However, the metabolic connection between toxic exposures and testicular dysfunction remains unclear.

RESULTS

In the present study, the metabolic disorder of testicular dysfunction was investigated using triptolide-induced testicular injury in mice. We found that triptolide induced spermine deficiency resulting from disruption of polyamine biosynthesis and uptake in testis, and perturbation of the gut microbiota. Supplementation with exogenous spermine reversed triptolide-induced testicular dysfunction through increasing the expression of genes related to early and late spermatogenic events, as well as increasing the reduced number of offspring. Loss of gut microbiota by antibiotic treatment resulted in depletion of spermine levels in the intestine and potentiation of testicular injury. Testicular dysfunction in triptolide-treated mice was reversed by gut microbial transplantation from untreated mice and supplementation with polyamine-producing Parabacteroides distasonis. The protective effect of spermine during testicular injury was largely dependent on upregulation of heat shock protein 70s (HSP70s) both in vivo and in vitro.

CONCLUSIONS

The present study linked alterations in the gut microbiota to testicular dysfunction through disruption of polyamine metabolism. The diversity and dynamics of the gut microbiota may be considered as a therapeutic option to prevent male infertility. Video Abstract.

A novel sulfamethoxazole derivative as an inhibitory agent against HSP70: A combination of computational with in vitro studies

In the current study, a novel derivative of sulfamethoxazole (a sulfonamide containing anti-biotic) named ZM-093 (IUPAC name: (E)-4-((4-(bis(2-hydroxyethyl)amino)phenyl)diazenyl)-N-(5-methylisoxazole-3-yl)benzenesulfonamide) was synthesized via common diazotization-coupling reactions from sulfamethoxazole and subsequently characterized through NMR/FT-IR spectroscopy. After evaluation, the compound was geometrically optimized at the DFT level of theory with BL3YP method and 6/31++G (d,p) basis set and from the optimized structure, several molecular descriptors important in the biological reactivity of the compound, such as global reactivity parameters, molecular electrostatic potential, average local ionization energy, and drug-likeness features of the compound were computationally analyzed. The experimental in vitro investigations of the interaction between ZM-093 and heat shock protein 70 (HSP70), a protein that is highly expressed in several types of cancers, exhibited a significant inhibitory effect against the chaperone activity of HSP70 for the titled compound (P-value < 0.01) and the comparison between the experimental studies with the mentioned computational analysis, as well as molecular docking, illustrated that ZM-093 may inhibit HSP70 through binding to its substrate-binding domain. Finally, by taking all the previous results into account, a new method for assessing the inhibitory activity of ligand to HSP70 is introduced based on protonography, a recently developed method that is dependent on the catalytic activity of carbonic anhydrase on polyacrylamide gel electrophoresis.

The role of heat shock proteins in neoplastic processes and the research on their importance in the diagnosis and treatment of cancer

Heat shock proteins (HSPs) are chaperones with highly conservative primary structure, necessary in the processes of protein folding to the most energetically advantageous conformation and maintaining their stability. HSPs perform a number of important functions in various cellular processes and are capable of modulating pathophysiological conditions at the cellular and systemic levels. An example is the high level of HSP expression in neoplastic tissues, which disrupts the apoptosis of transformed cells and promotes the processes of proliferation, invasion, and metastasis. In addition, an increasing amount of information is appearing about the participation of HSPs in the formation of multidrug resistance.This paper provides a review of the current state of research on the fundamental importance as well as the diagnostic and prognostic role of various classes of HSP in cancer treatment. It presents the prospects for using HSPs as biological markers of disease progression and targets in various cancer treatment strategies. However, the need for additional research is quite high. Only numerous joint efforts of research groups will allow the effective use of HSPs as a tool to combat cancer.

Arginine-Arginine-Leucine Peptide Targeting Heat Shock Protein 70 for Cancer Imaging

Arg-Arg-Leu (RRL) is a potent tumor-homing tripeptide. However, the binding target is unclear. In this study, we intended to identify the binding target of RRL and evaluate the tumor targeting of ^99mTc-MAG₃-RRL in vivo. Biotin-RRL, 5-TAMRA-RRL, and ^99mTc-MAG₃-RRL were designed to trace the binding target and tumor lesion. Immunoprecipitation-mass spectrometry was conducted to identify the candidate proteins and determination of the subcellular localization was also performed. A pull-down assay was performed to demonstrate the immunoprecipitate. Fluorescence colocalization and cell uptake assays were performed to elucidate the correlation between the selected binding protein and RRL, and the internalization mechanism of RRL. Biodistribution and in vivo imaging were performed to evaluate the tumor accumulation and targeting of ^99mTc-MAG₃-RRL. The target for RRL was screened to be heat shock protein 70 (HSP70). The prominent uptake distribution of RRL was concentrated in the membrane and cytoplasm. A pull-down assay demonstrated the existence of HSP70 in the biotin-RRL captured complex. Regarding fluorescence colocalization and cell uptake assays, RRL may interact with HSP70 at the nucleotide-binding domain (NBD). Clathrin-dependent endocytosis and macropinocytosis could be a vital internalization mechanism of RRL. In vivo imaging and biodistribution both demonstrated that ^99mTc-MAG₃-RRL can trace tumors with satisfactory accumulation in hepatoma xenograft mice. The radioactive signals accumulated in tumor lesions can be blocked by VER-155008, which can bind to the NBD of HSP70. Our findings revealed that RRL may interact with HSP70 and that ^99mTc-MAG₃-RRL could be a prospective probe for visualizing overexpressed HSP70 tumor sections.

Myoblast mechanotransduction and myotube morphology is dependent on BAG3 regulation of YAP and TAZ

Skeletal muscle tissue is mechanically dynamic with changes in stiffness influencing function, maintenance, and regeneration. We modeled skeletal muscle mechanical changes in culture with dynamically stiffening hydrogels demonstrating that the chaperone protein BAG3 transduces matrix stiffness by redistributing YAP and TAZ subcellular localization in muscle progenitor cells. BAG3 depletion increases cytoplasmic retention of YAP and TAZ, desensitizing myoblasts to changes in hydrogel elastic moduli. Upon differentiation, muscle progenitors depleted of BAG3 formed enlarged, round myotubes lacking the typical cylindrical morphology. The aberrant morphology is dependent on YAP/TAZ signaling, which was sequestered in the cytoplasm in BAG3-depleted myotubes but predominately nuclear in cylindrical myotubes of control cells. Control progenitor cells induced to differentiate on soft (E' = 4 and 12 kPa) hydrogels formed circular myotubes similar to those observed in BAG3-depleted cells. Inhibition of the Hippo pathway partially restored myotube morphologies, permitting nuclear translocation of YAP and TAZ in BAG3-depleted myogenic progenitors. Thus, BAG3 is a critical mediator of dynamic stiffness changes in muscle tissue, coupling mechanical alterations to intracellular signals and inducing changes in gene expression that influence muscle progenitor cell morphology and differentiation.

Therapeutic targeting of BAG3: considering its complexity in cancer and heart disease

Bcl2-associated athanogene-3 (BAG3) is expressed ubiquitously in humans, but its levels are highest in the heart, the skeletal muscle, and the central nervous system; it is also elevated in many cancers. BAG3's diverse functions are supported by its multiple protein-protein binding domains, which couple with small and large heat shock proteins, members of the Bcl2 family, other antiapoptotic proteins, and various sarcomere proteins. In the heart, BAG3 inhibits apoptosis, promotes autophagy, couples the β-adrenergic receptor with the L-type Ca2+ channel, and maintains the structure of the sarcomere. In cancer cells, BAG3 binds to and supports an identical array of prosurvival proteins, and it may represent a therapeutic target. However, the development of strategies to block BAG3 function in cancer cells may be challenging, as they are likely to interfere with the essential roles of BAG3 in the heart. In this Review, we present the current knowledge regarding the biology of this complex protein in the heart and in cancer and suggest several therapeutic options.

Extracellular vesicles from neurons promote neural induction of stem cells through cyclin D1

Extracellular vesicles (EVs) are thought to mediate the transport of proteins and RNAs involved in intercellular communication. Here, we show dynamic changes in the buoyant density and abundance of EVs that are secreted by PC12 cells stimulated with nerve growth factor (NGF), N2A cells treated with retinoic acid to induce neural differentiation, and mouse embryonic stem cells (mESCs) differentiated into neuronal cells. EVs secreted from in vitro differentiated cells promote neural induction of mESCs. Cyclin D1 enriched within the EVs derived from differentiated neuronal cells contributes to this induction. EVs purified from cells overexpressing cyclin D1 are more potent in neural induction of mESC cells. Depletion of cyclin D1 from the EVs reduced the neural induction effect. Our results suggest that EVs regulate neural development through sorting of cyclin D1.

Low-Temperature Photothermal Therapy: Strategies and Applications

Although photothermal therapy (PTT) with the assistance of nanotechnology has been considered as an indispensable strategy in the biomedical field, it still encounters some severe problems that need to be solved. Excessive heat can induce treated cells to develop thermal resistance, and thus, the efficacy of PTT may be dramatically decreased. In the meantime, the uncontrollable diffusion of heat can pose a threat to the surrounding healthy tissues. Recently, low-temperature PTT (also known as mild PTT or mild-temperature PTT) has demonstrated its remarkable capacity of conquering these obstacles and has shown excellent performance in bacterial elimination, wound healing, and cancer treatments. Herein, we summarize the recently proposed strategies for achieving low-temperature PTT based on nanomaterials and introduce the synthesis, characteristics, and applications of these nanoplatforms. Additionally, the combination of PTT and other therapeutic modalities for defeating cancers and the synergistic cancer therapeutic effect of the combined treatments are discussed. Finally, the current limitations and future directions are proposed for inspiring more researchers to make contributions to promoting low-temperature PTT toward more successful preclinical and clinical disease treatments.

Impaired HSP70 Expression in the Aorta of Female Rats: A Novel Insight Into Sex-Specific Differences in Vascular Function

Heat-shock protein 70 (HSP70) contributes to cellular calcium (Ca2+) handling mechanisms during receptor-mediated vascular contraction. Interestingly, previous studies have independently reported sex-related differences in HSP70 expression and Ca2+ dynamics. Still, it is unknown if sex, as a variable, plays a role in the impact that HSP70 has upon vascular contraction. To narrow this gap, we investigated if differences exist in the expression levels of HSP70 in the aorta, and if targeting this protein contributes to sex disparity in vascular responses. We report that, compared with male animals, female rats present a reduction in the basal levels of HSP70. More compelling, we found that the blockade of HSP70 has a greater impact on phenylephrine-induced phasic and tonic vascular contraction in female animals. In fact, it seems that the inhibition of HSP70 significantly affects vascular Ca2+ handling mechanisms in females, which could be associated with the fact that these animals have impaired HSP70 expression. Corroborating this idea, we uncovered that the higher sensitivity of female rats to HSP70 inhibition does not involve an increase in NO-dependent vasodilation nor a decrease in vascular oxidative stress. In summary, our findings reveal a novel mechanism associated with sex-specific differences in vascular responses to α-1 adrenergic stimulation, which might contribute to unraveling the network of intertwined pathways conferring female protection to (cardio)vascular diseases.

Hsp70 acts as a fine-switch that controls E3 ligase CHIP-mediated TAp63 and ΔNp63 ubiquitination and degradation

The major clinical problem in human cancer is metastasis. Metastases are the cause of 90% of human cancer deaths. TAp63 is a critical suppressor of tumorigenesis and metastasis. ΔNp63 acts as a dominant-negative inhibitor to block the function of p53 and TAp63. Although several ubiquitin E3 ligases have been reported to regulate p63 stability, the mechanism of p63 regulation remains partially understood. Herein, we show that CHIP, an E3 ligase with a U-box domain, physically interacts with p63 and promotes p63 degradation. Notably, Hsp70 depletion by siRNA stabilizes TAp63 in H1299 cells and destabilizes ΔNp63 in SCC9 cells. Loss of Hsp70 results in a reduction in the TAp63-CHIP interaction in H1299 cells and an increase in the interaction between ΔNp63 and CHIP in SCC9 cells. Our results reveal that Hsp70 acts as a molecular switch to control CHIP-mediated ubiquitination and degradation of p63 isoforms. Furthermore, regulation of p63 by the Hsp70-CHIP axis contributes to the migration and invasion of tumor cells. Hence, our findings demonstrate that Hsp70 is a crucial regulator of CHIP-mediated ubiquitination and degradation of p63 isoforms and identify a new pathway for maintaining TAp63 or ΔNp63 stability in cancers.

HSP70 inhibits pig pituitary gonadotrophin synthesis and secretion by regulating the corticotropin-releasing hormone signaling pathway and targeting SMAD3

High levels or long periods of stress have been shown to negatively impact cell homeostasis, including with respect to abnormalities in domestic animal reproduction, which are typically activated through the hypothalamus-pituitary-adrenal axis, in which corticotropin-releasing hormone (CRH) and heat shock protein 70 (HSP70) are involved. In addition, CRH has been reported to inhibit pituitary gonadotrophin synthesis, and HSP70 is expressed in the pituitary gland. The aim of this study was to determine whether HSP70 was involved in regulating gonadotrophin synthesis and secretion by mediating the CRH pathway in the porcine pituitary gland. Our results showed that HSP70 was highly expressed in the porcine pituitary gland, with over 90% of gonadotrophic cells testing HSP70 positive. The results of functional studies demonstrated that the HSP70 inducer decreased FSH and LH levels in cultured porcine primary pituitary cells, whereas an HSP70 inhibitor blocked the negative effect of CRH on gonadotrophin synthesis and secretion. Furthermore, our results demonstrated that HSP70 inhibited gonadotrophin synthesis and secretion by blocking GnRH-induced SMAD3 phosphorylation, which acts as the targeting molecule of HSP70, while CRH upregulated HSP70 expression through the PKC and ERK pathways. Collectively, these data demonstrate that HSP70 inhibits pituitary gonadotrophin synthesis and secretion by regulating the CRH signaling pathway and inhibiting SMAD3 phosphorylation, which are important for our understanding the mechanisms of the stress affects domestic animal reproductive functions.

Lysosomes in acute myeloid leukemia: potential therapeutic targets?

Lysosomes, since their discovery, have been primarily known for degrading cellular macromolecules. However, in recent studies, they have begun to emerge as crucial regulators of cell homeostasis. They are at the crossroads of catabolic and anabolic pathways and are intricately involved in cellular trafficking, nutrient signaling, energy metabolism, and immune regulation. Their involvement in such essential cellular functions has renewed clinical interest in targeting the lysosome as a novel way to treat disease, particularly cancer. Acute myeloid leukemia (AML) is an aggressive blood cancer with a low survival probability, particularly in older patients. The genomic landscape of AML has been extensively characterized but few targeted therapies (with the exception of differentiation therapy) can achieve a long-term cure. Therefore, there is an unmet need for less intensive and more tolerable therapeutic interventions. In this review, we will give an overview on the myriad of functions performed by lysosomes and their importance in malignant disease. Furthermore, we will discuss their relevance in hematopoietic cells and different ways to potentially target them in AML.

Hsp90 is involved in pseudorabies virus virion assembly via stabilizing major capsid protein VP5

Many viruses utilize molecular chaperone heat shock protein 90 (Hsp90) for protein folding and stabilization, however, the role of Hsp90 in herpesvirus lifecycle is obscure. Here, we provide evidence that Hsp90 participates in pseudorabies virus (PRV) replication. Viral growth kinetics assays show that Hsp90 inhibitor geldanamycin (GA) abrogates PRV replication at the post-penetration step. Transmission electron microscopy demonstrates that dysfunction of Hsp90 diminishes the quantity of PRV nucleocapsids. Overexpression and knockdown of Hsp90 suggest that de novo Hsp90 is involved in PRV replication. Mechanismly, dysfunction of Hsp90 inhibits PRV major capsid protein VP5 expression. Co-immunoprecipitation and indirect immunofluorescence assays indicate that Hsp90 interacts with VP5. Interestingly, Hsp70, a collaborator of Hsp90, also interacts with VP5, but doesn't affect PRV growth. Finally, inhibition of Hsp90 results in PRV VP5 degradation in a proteasome-dependent manner. Collectively, our data suggest that Hsp90 contributes to PRV virion assembly and replication via stabilization of VP5.

Hsp70 in cancer: A double agent in the battle between survival and death

The heat shock protein (Hsps) superfamily, also known as molecular chaperones, are highly conserved and present in all living organisms and play vital roles in protein fate. The HspA1A (Hsp70-1), called Hsp70 in this review, is expressed at low or undetectable levels in most unstressed normal cells, but numerous studies have shown that diverse types of tumor cells express Hsp70 at the plasma membrane that leads to resistance to programmed cell death and tumor progression. Hsp70 is released into the extracellular milieu in three forms including free soluble, complexed with cancer antigenic peptides, and exosome forms. Therefore, it seems to be a promising therapeutic target in human malignancies. However, a great number of studies have indicated that both intracellular and extracellular Hsp70 have a dual function. A line of evidence presented that intracellular Hsp70 has a cytoprotective function via suppression of apoptosis and lysosomal cell death (LCD) as well as that extracellular Hsp70 can promote tumorigenesis and angiogenesis. Other evidence showed intracellular Hsp70 can promote apoptosis and membrane-associated/extracellular Hsp70 can elicit antitumor innate and adaptive immune responses. Given the contradictory functions, as a "double agent," could Hsp70 be a promising tool in the future of targeted cancer therapies? To answer this question, in this review, we will discuss the functions of Hsp70 in cancers besides inhibition and stimulation strategies for targeting Hsp70 along with their challenges.

A Novel Inhibitor of HSP70 Induces Mitochondrial Toxicity and Immune Cell Recruitment in Tumors

The protein chaperone HSP70 is overexpressed in many cancers including colorectal cancer, where overexpression is associated with poor survival. We report here the creation of a uniquely acting HSP70 inhibitor (HSP70i) that targets multiple compartments in the cancer cell, including mitochondria. This inhibitor was mitochondria toxic and cytotoxic to colorectal cancer cells, but not to normal colon epithelial cells. Inhibition of HSP70 was efficacious as a single agent in primary and metastatic models of colorectal cancer and enabled identification of novel mitochondrial client proteins for HSP70. In a syngeneic colorectal cancer model, the inhibitor increased immune cell recruitment into tumors. Cells treated with the inhibitor secreted danger-associated molecular patterns (DAMP), including ATP and HMGB1, and functioned effectively as a tumor vaccine. Interestingly, the unique properties of this HSP70i in the disruption of mitochondrial function and the inhibition of proteostasis both contributed to DAMP release. This HSP70i constitutes a promising therapeutic opportunity in colorectal cancer and may exhibit antitumor activity against other tumor types. SIGNIFICANCE: These findings describe a novel HSP70i that disrupts mitochondrial proteostasis, demonstrating single-agent efficacy that induces immunogenic cell death in treated tumors.

Andrographolide Mitigates Unfolded Protein Response Pathway and Apoptosis Involved in Chikungunya Virus Infection

BACKGROUND

Chikungunya virus (CHIKV) is an arthropod-borne RNA virus which induces host Endoplasmic Reticulum (ER) stress by accumulating unfolded or misfolded proteins. ER stress activates the unfolded protein response (UPR) pathway to enable proper protein folding and maintain cellular homeostasis. There is no approved drug or vaccine available for CHIKV treatment, therefore, a pharmacological countermeasure is warranted for preventing CHIKV infection.

OBJECTIVE

With a view to find a treatment modality for chikungunya infection, "andrographolide", a plant-derived diterpenoid with reported antiviral, anti-inflammatory and immunomodulatory effects, was used to investigate its role in chikungunya induced unfolded protein stress and apoptosis.

METHODS

Cells and supernatant collected on andrographolide and VER-155008, a GRP78 inhibitor, treatment in CHIKV infected and mock-infected THP-1 cells were tested for differential expression of UPR pathway proteins including GRP78, PERK, EIF-2&#945;, IRE-1&#945;, XBP-1 and ATF6. Furthermore, the inflammasome and apoptosis pathway proteins, i.e., caspase-1, caspase-3 and PARP, were tested by immunoblotting, and cytokines, i.e., IL-1&#946;, IL-6 and IFN-&#947; were tested by ELISA.

RESULTS

Andrographolide treatment in CHIKV infected THP-1 cells significantly reduced IRE1α and downstream spliced XBP1 protein expression. Furthermore, CHIKV induced apoptosis and viral protein expression were also reduced on andrographolide treatment. A comparative analysis of andrographolide versus VER-155008, confirmed that andrographolide surpasses the effects of VER-155008 in suppressing the CHIKV induced ER stress.

CONCLUSION

The study, therefore, confirms that andrographolide is a potential remedy for chikungunya infection and suppresses CHIKV induced ER stress and apoptosis.

An additional physiological role for HSP70: Assistance of vascular reactivity

AIMS

HSP70, a molecular chaperone, helps to maintain proteostasis. In muscle biology, however, evidence suggests HSP70 to have a more versatile range of functions, as genetic deletion of its inducible genes impairs Ca²⁺ handling, and consequently, cardiac and skeletal muscle contractility. Still, it is unknown whether HSP70 is involved in vascular reactivity, an intrinsic physiological mechanism of blood vessels. Therefore, we designed this study to test the hypothesis that proper vascular reactivity requires the assistance of HSP70.

MAIN METHODS

We performed functional studies in a wire-myograph using thoracic aorta isolated from male Sprague Dawley rats. Experiments were conducted with and without an HSP70 inhibitor as well as in heat-stressed vessels. The expression levels of HSP70 were evaluated with Western blotting. NO and ROS levels were assessed with fluorescence microscopy.

KEY FINDINGS

We report that blockade of HSP70 weakens contraction in response to phenylephrine (dose-response) in the aorta. Additionally, we demonstrated that inhibition of HSP70 affects the amplitude of the fast and of the slow components of the time-force curve. Corroborating these findings, we found that inhibition of HSP70, in vessels over-expressing this protein, partly rescues the contractile phenotype of aortic rings. Furthermore, we show that blockade of HSP70 facilitates relaxation in response to acetylcholine and clonidine without affecting the basal levels of NO and ROS.

SIGNIFICANCE

Our work introduces an additional physiological role for HSP70, the assistance of vascular reactivity, which highlights this protein as a new player in vascular physiology, and therefore, uncovers a promising research avenue for vascular diseases.

HSC70 is required for infectious bursal disease virus (IBDV) infection in DF-1 cells

Background

Infectious bursal disease (IBD) is a highly contagious infectious disease that causes severe immunosuppression and damage to the bursa of Fabricius in chickens. Several proteins involved in IBD virus (IBDV) infection, such as surface immunoglobulin M, integrin, annexin A2 and chicken heat shock protein 90, have been identified. However, the main protein that plays key roles in virus infection has not yet been confirmed.

Methods

DF-1 cell line was transfected with the pcDNA-VP2 plasmid and analyzed by immunofluorescence assay. The proteins reacted with VP2 of IBDV in DF-1 cells were pulldown with the monoclonal antibody and identified by mass spectrometry. Heat shock cognate protein 70 (HSC70), one of these proteins, was selected to be investigated in the function in IBDV infection by specific antibody and its inhibitor.

Results

The DF-1 cell line was transfected with the pcDNA-VP2 plasmid, and expression of IBDV VP2 in DF-1 cells was confirmed by immunofluorescence assays. Heat shock cognate protein 70 (HSC70) was one of the proteins identified by coimmunoprecipitation using a monoclonal antibody (2H11) against VP2 and mass spectrometry analysis. IBDV infection in DF-1 cells was strongly inhibited by both an anti-HSC70 antibody and a HSC70 inhibitor (VER155008).

Conclusion

These results suggest that HSC70 may be an essential factor for IBDV infection.