Pathways of chaperone-mediated protein folding in the cytosol

Supramolecular nanoassembly of lysozyme and α-lactalbumin (apo α-LA) exhibits selective cytotoxicity and enhanced bioavailability of curcumin to cancer cells

Hybrid supramolecular spherical nanoassembly of hen egg white lysozyme and bovine apo α lactalbumin (SN_LYZ-BLA) was prepared with a mean size of ˜55.2 nm using an optimized desolvation method via chemical crosslinking. The nanoassembly, SN_LYZ-BLA demonstrated dose-dependent reactive oxygen species (ROS) mediated cytotoxicity in multiple cancer cells such as MCF-7, MDA-MB231, HeLa and MG 63. It also demonstrated high loading capacity of a phytochemical based anticancer agent, curcumin (248.8 mg/g) and target-based pH-responsive in vitro drug release with around 85.8% curcumin release observed under acidic condition. Moreover, curcumin loaded SN_LYZ-BLA (SN_LYZ-BLA-CUR) induced cell viability reduction in all cancer cells including mouse melanoma (B16F10) by more than 90% within 24 h. Further, SN_LYZ-BLA and SN_LYZ-BLA-CUR when conjugated with folic acid enhanced the cytotoxicity via folate receptor-based targeting. Both drug loading and release induced conformational change and folding reconstitution of the protein nano-assembly, respectively, which made the whole system an efficient therapeutic agent that works via a dual mode of action. We demonstrated that SN_LYZ-BLA and SN_LYZ-BLA-CUR were highly biocompatible in vitro. Therefore, our supramolecular protein nanoassembly loaded with curcumin could emerge as a comprehensive cancer therapeutics that acts via a strategic mode of dual therapeutic mechanisms.

Expression of immune, antioxidant and stress related genes in different organs of common carp exposed to indoxacarb

The aim of the present study was to investigate the effects of chronic exposure of common carp (Cyprinus carpio) to indoxacarb on immune, antioxidant and stress gene expression. After 21 days exposure to 0, 0.75, 1.5 and 3 ppm indoxacarb, expression of IL-1β, IL-8, IL-10, TNF-α, IFN-γ, SOD, CAT, HSP70, IGF-I and IGF-II were assessed in liver, kidney and gills. In general, exposure to low concentration of indoxacarb increased inflammatory cytokine gene expression (IL-1β, IL-8, IL-10, TNF-α and IFN-γ) and inhibits inflammatory cytokines' expression at higher concentrations. The assessment of antioxidant gene expression (SOD and CAT) in different organs indicate that they were increased by low concentrations of indoxacarb to deal with primary oxidative situation. However, higher concentrations of indoxacarb caused reduction in oxidative gene expression. IGF genes expression in liver significantly increased at a concentration of 0.75 ppm treatment, then it decreased at 1.5 ppm indoxacarb and increased again by increasing in the indoxacarb concentration to 3 ppm. The expression of HSP70 in kidney showed a significant elevation in 0.75 and 1.5 ppm treatments compared with 3 ppm treatment and the control group. The expression of this gene in liver was significantly increased in 1.5 and 3 ppm treatments. The same pattern of expression was also observed in gill. Overall, indoxacarb exposure affects common carp health at transcription levels. Changes in the genes expression generally suggest that indoxacarb exposure led to interference in inflammation, oxidative stress and tissue damage.

Human Stress-inducible Hsp70 Has a High Propensity to Form ATP-dependent Antiparallel Dimers That Are Differentially Regulated by Cochaperone Binding

Eukaryotic protein homeostasis (proteostasis) is largely dependent on the action of highly conserved Hsp70 molecular chaperones. Recent evidence indicates that, apart from conserved molecular allostery, Hsp70 proteins have retained and adapted the ability to assemble as functionally relevant ATP-bound dimers throughout evolution. Here, we have compared the ATP-dependent dimerization of DnaK, human stress-inducible Hsp70, Hsc70 and BiP Hsp70 proteins, showing that their dimerization propensities differ, with stress-inducible Hsp70 being predominantly dimeric in the presence of ATP. Structural analyses using hydrogen/deuterium exchange mass spectrometry, native electrospray ionization mass spectrometry and small-angle X-ray scattering revealed that stress-inducible Hsp70 assembles in solution as an antiparallel dimer with the intermolecular interface closely resembling the ATP-bound dimer interfaces captured in DnaK and BiP crystal structures. ATP-dependent dimerization of stress-inducible Hsp70 is necessary for its efficient interaction with Hsp40, as shown by experiments with dimerization-deficient mutants. Moreover, dimerization of ATP-bound Hsp70 is required for its participation in high molecular weight protein complexes detected ex vivo, supporting its functional role in vivo As human cytosolic Hsp70 can interact with tetratricopeptide repeat (TPR) domain containing cochaperones, we tested the interaction of Hsp70 ATP-dependent dimers with Chip and Tomm34 cochaperones. Although Chip associates with intact Hsp70 dimers to form a larger complex, binding of Tomm34 disrupts the Hsp70 dimer and this event plays an important role in Hsp70 activity regulation. In summary, this study provides structural evidence of robust ATP-dependent antiparallel dimerization of human inducible Hsp70 protein and suggests a novel role of TPR domain cochaperones in multichaperone complexes involving Hsp70 ATP-bound dimers.

Multifaceted C-terminus of HSP70-interacting protein regulates tumorigenesis via protein quality control

C-terminus of heat shock protein 70 (HSP70)-interacting protein (CHIP) is an E3 ligase involved in a variety of protein homeostasis events implicated in diverse signaling pathways. Its involvement in varied and even opposite signaling circuits might be due to its hallmark signature of associating with molecular chaperones, including HSP90 and HSP70. Together, these proteins may be pivotal in implementing protein quality control. A curious and puzzling aspect of the function of CHIP is its capability to induce protein degradation via the proteasome- or lysosome-dependent pathways. In addition, these pathways are combined with ubiquitin-dependent or -independent pathways. This review focuses on the role of CHIP in the development or suppression of tumorigenesis. CHIP can act as a tumor suppressor by downregulating various oncogenes. CHIP also displays an oncogenic feature involving the inhibition of diverse tumor suppressors, including proteins related to intrinsic and extrinsic apoptotic pathways. The ability of CHIP to exhibit dual roles in determining the fate of cells has not been studied analytically. However, its association with various proteins involved in protein quality control might play a major role. In this review, the mechanistic roles of CHIP in tumor formation based on the regulation of diverse proteins are discussed.

P209L mutation in Bag3 does not cause cardiomyopathy in mice

Bcl-2-associated athanogene 3 (BAG3) is a cochaperone protein and a central player of the cellular protein quality control system. BAG3 is prominently expressed in the heart and plays an essential role in cardiac protein homeostasis by interacting with chaperone heat shock proteins (HSPs) in large, functionally distinct multichaperone complexes. The BAG3 mutation of proline 209 to leucine (P209L), which resides in a critical region that mediates the direct interaction between BAG3 and small HSPs (sHSPs), is associated with cardiomyopathy in humans. However, the mechanism by which the BAG3 P209L missense mutation leads to cardiomyopathy remains unknown. To determine the molecular basis underlying the cardiomyopathy caused by the BAG3 P209L mutation, we generated a knockin (KI) mouse model in which the endogenous Bag3 gene was replaced with mutant Bag3 containing the P215L mutation, which is equivalent to the human P209L mutation. We performed physiological, histological, and biochemical analyses of Bag3 P209L KI mice to determine the functional, morphological, and molecular consequences of the P209L mutation. We found that Bag3 P209L KI mice exhibited normal cardiac function and morphology up to 16 mo of age. Western blot analysis further revealed that levels of sHSPs, stress-inducible HSPs, ubiquitinated proteins, and autophagy were unaffected in P209L mutant mouse hearts. In conclusion, the P209L mutation in Bag3 does not cause cardiomyopathy in mice up to 16 mo of age under baseline conditions. NEW & NOTEWORTHY Bcl-2-associated athanogene 3 (BAG3) P209L mutation is associated with human cardiomyopathy. A recent study reported that transgenic mice overexpressing human BAG3 P209L in cardiomyocytes have cardiac dysfunction. In contrast, our P209L mice that express mutant BAG3 at the same level as that of wild-type mice displayed no overt phenotype. Our results suggest that human cardiomyopathy may result from species-specific requirements for the conserved motif that is disrupted by P209L mutation or from genetic background-dependent effects.

Ushering in the cardiac role of Ubiquilin1

Protein quality control (PQC) mechanisms are essential for maintaining cardiac function, and alterations in this pathway influence multiple forms of heart disease. Since heart disease is the leading cause of death worldwide, understanding how the delicate balance between protein synthesis and degradation is regulated in the heart demands attention. The study by Hu et al. reveals that the extraproteasomal ubiquitin receptor Ubiquilin1 (Ubqln1) plays an important role in cardiac ubiquitination-proteasome coupling, particularly in response to myocardial ischemia/reperfusion injury, thereby suggesting that this may be a new avenue for therapeutics.

Multiple functionalities of molecular chaperones revealed through systematic mapping of their interaction networks

Chaperones are a highly interactive group of proteins that function globally in many cellular processes involved in maintaining protein homeostasis. Traditional biochemical assays typically do not provide a complete view of the intricate networks through which chaperones collaborate to promote proteostasis. Recent advances in high-throughput systematic analyses of chaperone interactions have uncovered that chaperones display a remarkable cooperativity in their interactions with numerous client proteins. This cooperativity has been found to be a fundamental aspect of a properly functioning cell. Aberrant formation or improper regulation of these interactions can easily lead to disease states. Herein, we provide an overview of the use of large-scale interaction assays, whether physical (protein-protein) or genetic (epistatic), to study chaperone interaction networks. Importantly, we discuss the ongoing need for such studies to determine the mechanisms by which protein homeostasis is controlled in the cell.

Compensatory increases of select proteostasis networks after Hsp70 inhibition in cancer cells

Cancer cells thrive when challenged with proteotoxic stress by inducing components of the protein folding, proteasome, autophagy and unfolded protein response (UPR) pathways. Consequently, specific molecular chaperones have been validated as targets for anti-cancer therapies. For example, inhibition of Hsp70 family proteins (hereafter Hsp70) in rhabdomyosarcoma triggers UPR induction and apoptosis. To define how these cancer cells respond to compromised proteostasis, we compared rhabdomyosarcoma cells that were sensitive (RMS13) or resistant (RMS13-R) to the Hsp70 inhibitor MAL3-101. We discovered that endoplasmic reticulum-associated degradation (ERAD) and autophagy were activated in RMS13-R cells, suggesting that resistant cells overcome Hsp70 ablation by increasing misfolded protein degradation. Indeed, RMS13-R cells degraded ERAD substrates more rapidly than RMS cells and induced the autophagy pathway. Surprisingly, inhibition of the proteasome or ERAD had no effect on RMS13-R cell survival, but silencing of select autophagy components or treatment with autophagy inhibitors restored MAL3-101 sensitivity and led to apoptosis. These data indicate a route through which cancer cells overcome a chaperone-based therapy, define how cells can adapt to Hsp70 inhibition, and demonstrate the value of combined chaperone and autophagy-based therapies.This article has an associated First Person interview with the first author of the paper.

A pathogenic homozygous variant of the BBS10 gene in a patient with Bardet Biedl syndrome

The Bardet-Biedl syndrome is an autosomal recessive hereditary disorder with vast locus heterogeneity that belongs to the so-called ciliopathies, whose proteins are localized in the primary cilia and present functional deficiency. The multisystemic features of the disease include ocular, renal, cognitive, skeletal, as well as gonadal involvement and obesity, among others, with high inter- and intrafamilial variability. We describe the clinical case of an adolescent male patient with Bardet-Biedl syndrome, including the approach, the results from a 22-gene sequencing panel, and the analysis of updated scientific literature. We collected the clinical data of the patient and, after obtaining the informed consent, we conducted a multigenic sequencing panel oriented to known implicated genes. The patient was born to consanguineous parents and was the first affected member of the family. He presented with postaxial polydactyly, obesity, micropenis, retinitis pigmentosa, and learning disability. The multigenic panel allowed the identification of the homozygous pathogenic variant c.39_46del in the BBS10 gene and in other BBS genes variants associated with obesity. As the Bardet-Biedl syndrome is a rare disease, it is challenging to interpret its pleiotropism and gene/allelic heterogeneity. Its confirmation by molecular tests allows an adequate approach, follow-up, and genetic counseling of the patient and the family.

Ssb2 is a novel factor in regulating synthesis and degradation of Gcn4 in Saccharomyces cerevisiae

Yeast cells respond to environmental stress by inducing the master regulator Gcn4 to control genes involved in biosynthesis of amino acids and purine pathways. Gcn4 is a member of the basic leucine Zipper family and binds directly as a homodimer to a conserved regulatory region of target genes. Ssb2 was discovered to rescue the mutant Gcn4 which has a point mutation that decreases DNA-binding affinity. Ssb2 is part of the Hsp70 protein family responsible for protein quality control and it is thought that Ssb2 assists the passage of nascent polypeptide chains from the ribosomes. To characterize the mechanism behind the rescue of the mutant gcn4 phenotype, transcriptional activity and protein levels of Gcn4 were analyzed. We found that Ssb2 improved the expression of Gcn4 target genes by increasing the DNA-binding affinity of gcn4 mutants to target gene promoters under conditions of amino acid starvation. Gcn4 levels increased at both translational and post-translational levels without regulating GCN4 steady-state mRNA levels. We also found that the nuclear export signal of Ssb2 is required for interaction with Gcn4 and rescue of the gcn4 mutant phenotype. These findings suggest that Ssb2 is a critical factor that modulates Gcn4 functions in the nucleus and cytosol.

Comparative proteomic analysis revealed complex responses to classical/novel duck reovirus infections in Cairna moschata

Duck reovirus (DRV) is an typical aquatic bird pathogen belonging to the Orthoreovirus genus of the Reoviridae family. Reovirus causes huge economic losses to the duck industry. Although DRV has been identified and isolated long ago, the responses of Cairna moschata to classical/novel duck reovirus (CDRV/NDRV) infections are largely unknown. To investigate the relationship of pathogenesis and immune response, proteomes of C. moschata liver cells under the C/NDRV infections were analyzed, respectively. In total, 5571 proteins were identified, among which 5015 proteins were quantified. The differential expressed proteins (DEPs) between the control and infected liver cells displayed diverse biological functions and subcellular localizations. Among the DEPs, most of the metabolism-related proteins were down-regulated, suggesting a decrease in the basal metabolisms under C/NDRV infections. Several important factors in the complement, coagulation and fibrinolytic systems were significantly up-regulated by the C/NDRV infections, indicating that the serine protease-mediated innate immune system might play roles in the responses to the C/NDRV infections. Moreover, a number of molecular chaperones were identified, and no significantly changes in their abundances were observed in the liver cells. Our data may give a comprehensive resource for investigating the regulation mechanism involved in the responses of C. moschata to the C/NDRV infections.

Understanding the regulatory mechanisms of milk production using integrative transcriptomic and proteomic analyses: improving inefficient utilization of crop by-products as forage in dairy industry

BACKGROUND

Bovine milk is an important nutrient source for humans. Forage plays a vital role in dairy husbandry via affecting milk quality and quantity. However, the differences in mammary metabolism of dairy cows fed different forages remain elucidated. In this study, we utilized transcriptomic RNA-seq and iTRAQ proteomic techniques to investigate and integrate the differences of molecular pathways and biological processes in the mammary tissues collected from 12 lactating cows fed corn stover (CS, low-quality, n = 6) and alfalfa hay (AH, high-quality, n = 6).

RESULTS

A total of 1631 differentially expressed genes (DEGs; 1046 up-regulated and 585 down-regulated) and 346 differentially expressed proteins (DEPs; 138 increased and 208 decreased) were detected in the mammary glands between the CS- and AH-fed animals. Expression patterns of 33 DEPs (18 increased and 15 decreased) were consistent with the expression of their mRNAs. Compared with the mammary gland of AH-fed cows, the marked expression changes found in the mammary gland of CS group were for genes involved in reduced mammary growth/development (COL4A2, MAPK3, IKBKB, LGALS3), less oxidative phosphorylation (ATPsynGL, ATP6VOA1, ATP5H, ATP6VOD1, NDUFC1), enhanced lipid uptake/metabolism (SLC27A6, FABP4, SOD2, ACADM, ACAT1, IDH1, SCP2, ECHDC1), more active fatty acid beta-oxidation (HMGCS1), less amino acid/protein transport (SLC38A2, SLC7A8, RAB5a, VPS18), reduced protein translation (RPS6, RPS12, RPS16, RPS19, RPS20, RPS27), more proteasome- (PSMC2, PSMC6, PSMD14, PSMA2, PSMA3) and ubiquitin-mediated protein degradation (UBE2B, UBE2H, KLHL9, HSPH1, DNAJA1 and CACYBP), and more protein disassembly-related enzymes (SEC63, DNAJC3, DNAJB1, DNAJB11 and DNAJC12).

CONCLUSION

Our results indicate that the lower milk production in the CS-fed dairy cows compared with the AH-fed cows was associated with a network of mammary gene expression changes, importantly, the prime factors include decreased energy metabolism, attenuated protein synthesis, enhanced protein degradation, and the lower mammary cell growth. The present study provides insights into the effects of the varying quality of forages on mammary metabolisms, which can help the improvement of strategies in feeding dairy cows with CS-based diet.

Using Single-Molecule Approaches to Understand the Molecular Mechanisms of Heat-Shock Protein Chaperone Function

The heat-shock proteins (Hsp) are a family of molecular chaperones, which collectively form a network that is critical for the maintenance of protein homeostasis. Traditional ensemble-based measurements have provided a wealth of knowledge on the function of individual Hsps and the Hsp network; however, such techniques are limited in their ability to resolve the heterogeneous, dynamic and transient interactions that molecular chaperones make with their client proteins. Single-molecule techniques have emerged as a powerful tool to study dynamic biological systems, as they enable rare and transient populations to be identified that would usually be masked in ensemble measurements. Thus, single-molecule techniques are particularly amenable for the study of Hsps and have begun to be used to reveal novel mechanistic details of their function. In this review, we discuss the current understanding of the chaperone action of Hsps and how gaps in the field can be addressed using single-molecule methods. Specifically, this review focuses on the ATP-independent small Hsps and the broader Hsp network and describes how these dynamic systems are amenable to single-molecule techniques.

Biomedical Informatics on the Cloud: A Treasure Hunt for Advancing Cardiovascular Medicine

In the digital age of cardiovascular medicine, the rate of biomedical discovery can be greatly accelerated by the guidance and resources required to unearth potential collections of knowledge. A unified computational platform leverages metadata to not only provide direction but also empower researchers to mine a wealth of biomedical information and forge novel mechanistic insights. This review takes the opportunity to present an overview of the cloud-based computational environment, including the functional roles of metadata, the architecture schema of indexing and search, and the practical scenarios of machine learning-supported molecular signature extraction. By introducing several established resources and state-of-the-art workflows, we share with our readers a broadly defined informatics framework to phenotype cardiovascular health and disease.

Targeting the Hsp90-Cdc37-client protein interaction to disrupt Hsp90 chaperone machinery

Heat shock protein 90 (Hsp90) is a critical molecular chaperone protein that regulates the folding, maturation, and stability of a wide variety of proteins. In recent years, the development of Hsp90-directed inhibitors has grown rapidly, and many of these inhibitors have entered clinical trials. In parallel, the functional dissection of the Hsp90 chaperone machinery has highlighted the activity disruption of Hsp90 co-chaperone as a potential target. With the roles of Hsp90 co-chaperones being elucidated, cell division cycle 37 (Cdc37), a ubiquitous co-chaperone of Hsp90 that directs the selective client proteins into the Hsp90 chaperone cycle, shows great promise. Moreover, the Hsp90-Cdc37-client interaction contributes to the regulation of cellular response and cellular growth and is more essential to tumor tissues than normal tissues. Herein, we discuss the current understanding of the clients of Hsp90-Cdc37, the interaction of Hsp90-Cdc37-client protein, and the therapeutic possibilities of targeting Hsp90-Cdc37-client protein interaction as a strategy to inhibit Hsp90 chaperone machinery to present new insights on alternative ways of inhibiting Hsp90 chaperone machinery.

Hyperthermia-mediated drug delivery induces biological effects at the tumor and molecular levels that improve cisplatin efficacy in triple negative breast cancer

Triple negative breast cancer is an aggressive disease that accounts for at least 15% of breast cancer diagnoses, and a disproportionately high percentage of breast cancer related morbidity. Intensive research efforts are focused on the development of more efficacious treatments for this disease, for which therapeutic options remain limited. The high incidence of mutations in key DNA repair pathways in triple negative breast cancer results in increased sensitivity to DNA damaging agents, such as platinum-based chemotherapies. Hyperthermia has been successfully used in breast cancer treatment to sensitize tumors to radiation therapy and chemotherapy. It has also been used as a mechanism to trigger drug release from thermosensitive liposomes. In this study, mild hyperthermia is used to trigger release of cisplatin from thermosensitive liposomes in the vasculature of human triple negative breast cancer tumors implanted orthotopically in mice. This heat-triggered liposomal formulation of cisplatin resulted in significantly delayed tumor growth and improved overall survival compared to treatment with either non-thermosensitive liposomes containing cisplatin or free cisplatin, as was observed in two independent tumor models (i.e. MDA-MB-231 and MDA-MB-436). The in vitro sensitivity of the cell lines to cisplatin and hyperthermia alone and in combination was characterized extensively using enzymatic assays, clonogenic assays, and spheroid growth assays. Evaluation of correlations between the in vitro and in vivo results served to identify the in vitro approach that is most predictive of the effects of hyperthermia in vivo. Relative expression of several heat shock proteins and the DNA damage repair protein BRCA1 were assayed at baseline and in response to hyperthermia both in vitro and in vivo. Interestingly, delivery of cisplatin in thermosensitive liposomes in combination with hyperthermia resulted in the most significant tumor growth delay, relative to free cisplatin, in the less cisplatin-sensitive cell line (i.e. MDA-MB-231). This work demonstrates that thermosensitive cisplatin liposomes used in combination with hyperthermia offer a novel method for effective treatment of triple negative breast cancer.

Aggregating sequences that occur in many proteins constitute weak spots of bacterial proteostasis

Aggregation is a sequence-specific process, nucleated by short aggregation-prone regions (APRs) that can be exploited to induce aggregation of proteins containing the same APR. Here, we find that most APRs are unique within a proteome, but that a small minority of APRs occur in many proteins. When aggregation is nucleated in bacteria by such frequently occurring APRs, it leads to massive and lethal inclusion body formation containing a large number of proteins. Buildup of bacterial resistance against these peptides is slow. In addition, the approach is effective against drug-resistant clinical isolates of Escherichiacoli and Acinetobacterbaumannii, reducing bacterial load in a murine bladder infection model. Our results indicate that redundant APRs are weak points of bacterial protein homeostasis and that targeting these may be an attractive antibacterial strategy.

Aggregation is sequence-specific and nucleated by short aggregating protein segments (APR). Here authors use a multidisciplinary approach to show that in E.coli some frequently occurring APRs lead to protein aggregation and ultimately bacterial cell death, which could serve as antibacterial strategy.

Emerging roles and underlying molecular mechanisms of DNAJB6 in cancer

DNAJB6 also known as mammalian relative of DnaJ (MRJ) encodes a highly conserved member of the DnaJ/Hsp40 family of co-chaperone proteins that function with Hsp70 chaperones. DNAJB6 is widely expressed in all tissues, with higher expression levels detected in the brain. DNAJB6 is involved in diverse cellular functions ranging from murine placental development, reducing the formation and toxicity of mis-folded protein aggregates, to self-renewal of neural stem cells. Involvement of DNAJB6 is implicated in multiple pathologies such as Huntington's disease, Parkinson's diseases, limb-girdle muscular dystrophy, cardiomyocyte hypertrophy and cancer. This review summarizes the important involvement of the spliced isoforms of DNAJB6 in various pathologies with a specific focus on the emerging roles of human DNAJB6 in cancer and the underlying molecular mechanisms.

A systematic atlas of chaperome deregulation topologies across the human cancer landscape

Proteome balance is safeguarded by the proteostasis network (PN), an intricately regulated network of conserved processes that evolved to maintain native function of the diverse ensemble of protein species, ensuring cellular and organismal health. Proteostasis imbalances and collapse are implicated in a spectrum of human diseases, from neurodegeneration to cancer. The characteristics of PN disease alterations however have not been assessed in a systematic way. Since the chaperome is among the central components of the PN, we focused on the chaperome in our study by utilizing a curated functional ontology of the human chaperome that we connect in a high-confidence physical protein-protein interaction network. Challenged by the lack of a systems-level understanding of proteostasis alterations in the heterogeneous spectrum of human cancers, we assessed gene expression across more than 10,000 patient biopsies covering 22 solid cancers. We derived a novel customized Meta-PCA dimension reduction approach yielding M-scores as quantitative indicators of disease expression changes to condense the complexity of cancer transcriptomics datasets into quantitative functional network topographies. We confirm upregulation of the HSP90 family and also highlight HSP60s, Prefoldins, HSP100s, ER- and mitochondria-specific chaperones as pan-cancer enriched. Our analysis also reveals a surprisingly consistent strong downregulation of small heat shock proteins (sHSPs) and we stratify two cancer groups based on the preferential upregulation of ATP-dependent chaperones. Strikingly, our analyses highlight similarities between stem cell and cancer proteostasis, and diametrically opposed chaperome deregulation between cancers and neurodegenerative diseases. We developed a web-based Proteostasis Profiler tool (Pro²) enabling intuitive analysis and visual exploration of proteostasis disease alterations using gene expression data. Our study showcases a comprehensive profiling of chaperome shifts in human cancers and sets the stage for a systematic global analysis of PN alterations across the human diseasome towards novel hypotheses for therapeutic network re-adjustment in proteostasis disorders.

Protein homeostasis, or proteostasis, is maintained by the proteostasis network (PN), an intricately regulated modular network of interacting processes that evolved to balance the native proteome, supporting cellular and organismal health throughout lifespan. Imbalances and collapse of cellular proteostasis capacity, the capacity to buffer against cytotoxic damage and stress, is increasingly implicated in some of the most challenging diseases of our time, including neurodegeneration and cancers. The systems-level PN alterations in these diseases are not understood to date. Here, we address this challenge, focussing on the human chaperome, the ensemble of chaperones and co-chaperones, which represents a central conserved PN functional arm. We devised a novel data dimensionality reduction approach enabling quantitative contextual visualization of chaperome alterations in the heterogeneous spectrum of cancers based on gene expression data from thousands of patient biopsies. We developed Proteostasis Profiler (Pro²), a new web-tool enabling intuitive visualisation of cancer chaperome deregulation maps. We stratify two cancer groups based on diverging chaperome deregulation and highlight similarities between cancer and stem cell proteostasis. Our study also exposes drastically opposed shifts between cancers and neurodegenerative diseases. Collectively, this study sets the stage for a systematic global analysis of PN alterations across the human diseasome.

Hsp70: A Cancer Target Inside and Outside the Cell

Heat shock protein 70 (Hsp70) is the most ubiquitous stress-inducible chaperone. It accumulates in the cells in response to a wide variety of physiological and environmental insults including anticancer chemotherapy, thus allowing the cell to survive to lethal conditions. Intracellular Hsp70 is viewed as a cytoprotective protein. Indeed, this protein can inhibit key effectors of the apoptotic and autophagy machineries. In cancer cells, the expression of Hsp70 is abnormally high, and Hsp70 may participate in oncogenesis and in resistance to chemotherapy. In rodent models, Hsp70 overexpression increases tumor growth and metastatic potential. Depletion or inhibition of Hsp70 frequently reduces the size of the tumors and can even cause their complete involution. However, HSP70 is also found in the extra-cellular space where it may signal via membrane receptors or endosomes to alter gene transcription and cellular function. Overall, Hsp70 extracellular function is believed to be immnunogenic and the term chaperokine to define the extracellular chaperones such as Hsp70 has been advanced. In this chapter the knowledge to date, as well as some emerging paradigms about the intra- and extra-cellular functions of Hsp70, are presented. The strategies targeting Hsp70 that are being developed in cancer therapy will also be discussed.

SUMO E3 Ligase SlSIZ1 Facilitates Heat Tolerance in Tomato

High temperature has become a major abiotic stress that limits crop productivity. Heat shock transcription factors (HSFs) and heat shock proteins (HSPs) play important roles in enhancing thermotolerance of plants. SUMOylation is an important post-translational modification in regulating cellular functions in eukaryotes. SIZ1, a well-characterized SUMO E3 ligase, mediates the process of SUMOylation. In this study, SUMO conjugations were clearly induced by high temperature. Overexpression of SIZ1 SUMO E3 ligase (SlSIZ1) in tomato could enhance the tolerance to heat stress in tomato. The RNA interference (RNAi) plants were more wilted than the wild type with heat treatment. Under heat stress, SlSIZ1 could decrease the accumulation of reactive oxygen species (ROS) and induce some genes of HSF and HSP transcription. Furthermore, overexpression of SlSIZ1 could increase the level of Hsp70 under high temperature. Yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays showed that SlSIZ1 could interact with SlHsfA1 to mediate the SUMOylation of SlHsfA1 and consequently enhance thermotolerance of tomato. In conclusion, overexpression of SlSIZ1 enhanced heat tolerance by regulating the activities of HsfA1 and increasing the content Hsp70.

Cryopreservation Protocols for Human Adipose Tissue Derived Adult Stem Cells

The development of simple but effective storage protocols for adult stem cells will greatly enhance their use and utility in tissue-engineering applications. Cryopreservation has shown to be most promising but is a fairly complex process, necessitating the use of chemicals called cryoprotective agents (CPAs), freezing equipment, and obviously, storage in liquid nitrogen. The purpose of this chapter is to present a general overview of cryopreservation storage techniques and the optimal protocols/results obtained in our laboratory for long-term storage of adult stem cells using freezing storage.

PRDM14 directly interacts with heat shock proteins HSP90α and glucose-regulated protein 78

PRDM14 is overexpressed in various cancers and can regulate cancer phenotype under certain conditions. Inhibiting PRDM14 expression in breast and pancreatic cancers has been reported to reduce cancer stem‐like phenotypes, which are associated with aggressive tumor properties. Therefore, PRDM14 is considered a promising target for cancer therapy. To develop a pharmaceutical treatment, the mechanism and interacting partners of PRDM14 need to be clarified. Here, we identified the proteins interacting with PRDM14 in triple‐negative breast cancer (TNBC) cells, which do not express the three most common types of receptor (estrogen receptors, progesterone receptors, and HER2). We obtained 13 candidates that were pulled down with PRDM14 in TNBC HCC1937 cells and identified them by mass spectrometry. Two candidates—glucose‐regulated protein 78 (GRP78) and heat shock protein 90‐α (HSP90α)—were confirmed in immunoprecipitation assay in two TNBC cell lines (HCC1937 and MDA‐MB231). Surface plasmon resonance analysis using GST‐PRDM14 showed that these two proteins directly interacted with PRDM14 and that the interactions required the C‐terminal region of PRDM14, which includes zinc finger motifs. We also confirmed the interactions in living cells by NanoLuc luciferase‐based bioluminescence resonance energy transfer (NanoBRET) assay. Moreover, HSP90 inhibitors (17DMAG and HSP990) significantly decreased breast cancer stem‐like CD24⁻ CD44⁺ and side population (SP) cells in HCC1937 cells, but not in PRDM14 knockdown HCC1937 cells. The combination of the GRP78 inhibitor HA15 and PRDM14 knockdown significantly decreased cell proliferation and SP cell number in HCC1937 cells. These results suggest that HSP90α and GRP78 interact with PRDM14 and participate in cancer regulation.

Atomistic simulations and network-based modeling of the Hsp90-Cdc37 chaperone binding with Cdk4 client protein: A mechanism of chaperoning kinase clients by exploiting weak spots of intrinsically dynamic kinase domains

A fundamental role of the Hsp90 and Cdc37 chaperones in mediating conformational development and activation of diverse protein kinase clients is essential in signal transduction. There has been increasing evidence that the Hsp90-Cdc37 system executes its chaperoning duties by recognizing conformational instability of kinase clients and modulating their folding landscapes. The recent cryo-electron microscopy structure of the Hsp90-Cdc37-Cdk4 kinase complex has provided a framework for dissecting regulatory principles underlying differentiation and recruitment of protein kinase clients to the chaperone machinery. In this work, we have combined atomistic simulations with protein stability and network-based rigidity decomposition analyses to characterize dynamic factors underlying allosteric mechanism of the chaperone-kinase cycle and identify regulatory hotspots that control client recognition. Through comprehensive characterization of conformational dynamics and systematic identification of stabilization centers in the unbound and client- bound Hsp90 forms, we have simulated key stages of the allosteric mechanism, in which Hsp90 binding can induce instability and partial unfolding of Cdk4 client. Conformational landscapes of the Hsp90 and Cdk4 structures suggested that client binding can trigger coordinated dynamic changes and induce global rigidification of the Hsp90 inter-domain regions that is coupled with a concomitant increase in conformational flexibility of the kinase client. This process is allosteric in nature and can involve reciprocal dynamic exchanges that exert global effect on stability of the Hsp90 dimer, while promoting client instability. The network-based rigidity analysis and emulation of thermal unfolding of the Cdk4-cyclin D complex and Hsp90-Cdc37-Cdk4 complex revealed weak spots of kinase instability that are present in the native Cdk4 structure and are targeted by the chaperone during client recruitment. Our findings suggested that this mechanism may be exploited by the Hsp90-Cdc37 chaperone to recruit and protect intrinsically dynamic kinase clients from degradation. The results of this investigation are discussed and interpreted in the context of diverse experimental data, offering new insights into mechanisms of chaperone regulation and binding.

Differential proteomic analysis of platelets suggested target-related proteins in rabbit platelets treated with Rhizoma Corydalis

CONTEXT

Corydalis yanhusuo W.T. Wang (Papaveraceae) (Rhizoma Corydalis) showed inhibitory effects on rabbit platelet aggregation induced by ADP, thrombin (THR) or arachidonic acid (AA).

OBJECTIVE

This study separates and identifies the possible target-related platelet proteins and suggests possible signal cascades of RC antiplatelet aggregation.

MATERIALS AND METHODS

Based on comparative proteomics, the differentially expressed platelet proteins treated before and after with 50 mg/mL RC 90% ethanol extract (for 15 min at 37 °C) were analyzed and identified by two dimensional gel electrophoresis (2-DE) and MALDI-TOF-MS/MS. To further verify the possible signalling pathways of RC antiplatelet aggregation function, the concentration of calcium (Ca²⁺) was measured by Fura-2/AM fluorescence (Ex 340/380 nm, Em 500 nm) (RC final concentrations of 0.0156-0.1563 mg/mL), the levels of P-selectin and cyclic guanosine monophosphate (cGMP) were quantified by ELISA (OD. 450 nm) (RC final concentrations of 0.0156-1.5625 mg/mL), and the 5-hydroxytryptamine (5-HT) level was measured using ortho-phthalaldehyde (OPT) fluorescence (Ex 340 nm, Em 470 nm) (RC final concentrations of 0.3125-1.5625 mg/mL).

RESULTS

The expression of 52 proteins were altered in rabbit platelets after the treatment and the MALDI-TOF-MS analysis indicated that those proteins include 12 cytoskeleton proteins, 7 cell signalling proteins, 3 molecular chaperone proteins, 6 proteins related to platelet function, 16 enzymes and 7 other related proteins. Furthermore, RC extract could decrease the levels of 5-HT [inhibition rate of 96.80% (p < 0.05, vs. THR-activated group) treated with 0.7813 mg/mL of RC], Ca²⁺[172.73 ± 5.07 to 113.56 ± 5.46 nM (p < 0.001, vs. THR-activated group) treated with 0.0313 mg/mL of RC] and P-selectin [13.48 ± 0.96 ng/3 × 10⁸ to 11.64 ± 0.17 ng/3 × 10⁸ (p < 0.05, vs. THR-activated group) treated with 0.0156 mg/mL of RC], and increase in cGMP level [38.93 ± 0.57 to 50.26 ± 4.05 ng/3 × 10⁸ (p < 0.05, vs. THR-activated group) treated with 1.5165 mg/mL of RC] in ADP (10 μmol/L), THR (0.25 u/mL) or AA-(0.205 mmol/L) activated rabbit platelets.

DISCUSSION AND CONCLUSION

The present study indicated that P2Y12 receptor might be one of the direct target proteins of RC in platelets. The signal cascades network of RC after binding with P2Y12 receptor is mediating Gαi proteins to activate downstream signalling pathways (AC and/or PI3K signalling pathways) for the inhibition of platelet aggregation.

Metabolic Perturbations in a Bacillus subtilis clpP Mutant during Glucose Starvation

Proteolysis is essential for all living organisms to maintain the protein homeostasis and to adapt to changing environmental conditions. ClpP is the main protease in Bacillus subtilis, and forms complexes with different Clp ATPases. These complexes play crucial roles during heat stress, but also in sporulation or cell morphology. Especially enzymes of cell wall-, amino acid-, and nucleic acid biosynthesis are known substrates of the protease ClpP during glucose starvation. The aim of this study was to analyze the influence of a clpP mutation on the metabolism in different growth phases and to search for putative new ClpP substrates. Therefore, B. subtilis 168 cells and an isogenic ∆clpP mutant were cultivated in a chemical defined medium, and the metabolome was analyzed by a combination of ¹H-NMR, HPLC-MS, and GC-MS. Additionally, the cell morphology was investigated by electron microscopy. The clpP mutant showed higher levels of most glycolytic metabolites, the intermediates of the citric acid cycle, amino acids, and peptidoglycan precursors when compared to the wild-type. A strong secretion of overflow metabolites could be detected in the exo-metabolome of the clpP mutant. Furthermore, a massive increase was observed for the teichoic acid metabolite CDP-glycerol in combination with a swelling of the cell wall. Our results show a recognizable correlation between the metabolome and the corresponding proteome data of B. subtilisclpP mutant. Moreover, our results suggest an influence of ClpP on Tag proteins that are responsible for teichoic acids biosynthesis.

Nuclear heat shock protein 110 expression is associated with poor prognosis and hyperthermo-chemotherapy resistance in gastric cancer patients with peritoneal metastasis

AIM

To investigate the significance of heat shock protein 110 (HSP110) in gastric cancer (GC) patients with peritoneal metastasis undergoing hyperthermo-chemotherapy.

METHODS

Primary GC patients (n = 14) with peritoneal metastasis or positive peritoneal lavage cytology who underwent distal or total gastrectomy between April 2000 and December 2011 were enrolled in this study. The patients underwent postoperative intraperitoneal hyperthermo-chemotherapy using a Thermotron RF-8 heating device two weeks after surgery. We analyzed nuclear HSP110 expression in surgically resected tumors using immunohistochemistry. Additionally, the effect of HSP110 suppression on hyptherthermo-chemosensitivity was assessed in vitro in the MKN45 GC cell line using the HSP inhibitor KNK437.

RESULTS

HSP110 immnohistochemical staining in 14 GC patients showed that five (35.7%) samples belonged to the low expression group, and nine (64.3%) samples belonged to the high expression group. Progression-free survival was significantly shorter in the HSP110 high-expression group than in the low-expression group (P = 0.0313). However, no significant relationships were identified between HSP110 expression and the clinicopathological characteristics of patients. Furthermore, high HSP110 expression was not an independent prognostic factor in GC patients with peritoneal metastasis (P = 0.0625). HSP110 expression in MKN45 cells was suppressed by KNK437 at the hyperthermic temperature of 43 °C in vitro. Comparison of MKN45 cell proliferation in the presence and absence of KNK437 at 43 °C, revealed that proliferation was significantly decreased when HSP110 was inhibited by KNK437. Additionally, HSP110 suppression via HSP inhibitor treatment increased cellular sensitivity to hyperthermo-chemotherapy in vitro.

CONCLUSION

The expression of nuclear HSP110 in GC patients might be a new marker of chemosensitivity and a therapeutic target for patients who are tolerant to existing hyperthermo-chemotherapies.

Autocrine STIP1 signaling promotes tumor growth and is associated with disease outcome in hepatocellular carcinoma

Stress-induced phosphoprotein 1 (STIP1) is an adaptor protein that bridges between HSP70 and HSP90 folding and a secretory protein which regulates malignant cell growth. However, the role of STIP1 in hepatocellular carcinoma (HCC) remains unknown. Here, we found high expression of STIP1 in tumors was associated with worse overall survival (41.3 vs 62.7 months, P < 0.001) in 231 HCC patients. STIP1 was overexpressed in HCC tissues compared to adjacent non-tumor liver tissue (64.9% vs 4.0% P < 0.001), and serum STIP1 levels of HCC patients were elevated compared to healthy controls (P < 0.001). Mechanistically, STIP1 promoted HCC growth through PI3K-AKT-dependent anti-apoptotic pathway. STIP1 mediated cell growth in an autocrine fashion, which could be suppressed either by neutralizing extracellular STIP1 or by knocking down intracellular STIP1. In xenograft mouse model, knockdown of STIP1 significantly reduced tumor growth (P < 0.001). In conclusion, STIP1 is upregulated in HCC and associated with poor clinical prognosis. Blocking STIP1 activity suppresses HCC cell growth, providing the rationale for STIP1 as a potential therapeutic target in HCC.

HSF-1 is a regulator of miRNA expression in Caenorhabditis elegans

The ability of an organism to sense and adapt to environmental stressors is essential for proteome maintenance and survival. The highly conserved heat shock response is a survival mechanism employed by all organisms, including the nematode Caenorhabditis elegans, upon exposure to environmental extremes. Transcriptional control of the metazoan heat shock response is mediated by the heat shock transcription factor HSF-1. In addition to regulating global stress-responsive genes to promote stress-resistance and survival, HSF-1 has recently been shown to regulate stress-independent functions in controlling development, metabolism, and longevity. However, the indirect role of HSF-1 in coordinating stress-dependent and -independent processes through post-transcriptional regulation is largely unknown. MicroRNAs (miRNAs) have emerged as a class of post-transcriptional regulators that control gene expression through translational repression or mRNA degradation. To determine the role of HSF-1 in regulating miRNA expression, we have performed high-throughput small RNA-sequencing in C. elegans grown in the presence and absence of hsf-1 RNAi followed by treatment with or without heat shock. This has allowed us to uncover the miRNAs regulated by HSF-1 via heat-dependent and -independent mechanisms. Integrated miRNA/mRNA target-prediction analyses suggest HSF-1 as a post-transcriptional regulator of development, metabolism, and longevity through regulating miRNA expression. This provides new insight into the possible mechanism by which HSF-1 controls these processes. We have also uncovered oxidative stress response factors and insulin-like signaling factors as a common link between processes affected by HSF-1-regulated miRNAs in stress-dependent and -independent mechanisms, respectively. This may provide a role for miRNAs in regulating cross-talk between various stress responses. Our work therefore uncovers an interesting potential role for HSF-1 in post-transcriptionally controlling gene expression in C. elegans, and suggests a mechanism for cross-talk between stress responses.

Substrate specificity in the context of molecular chaperones

Molecular chaperones are one of the key players in protein biology and as such their structure and mechanism of action have been extensively studied. However the substrate specificity of molecular chaperones has not been well investigated. This review aims to summarize what is known about the substrate specificity and substrate recognition motifs of chaperones so as to better understand what substrate specificity means in the context of molecular chaperones. Available literature shows that the majority of chaperones have broad substrate range and recognize non-native conformations of proteins depending on recognition of hydrophobic and/or charged patches. Based on these recognition motifs chaperones can select for early, mid or late folding intermediates. Another major contributor to chaperone specificity are the co-chaperones they interact with as well as the sub-cellular location they are expressed in and the inducability of their expression. Some chaperones which have only one or a few known substrates are reported. In their case the mode of recognition seems to be specific structural complementarity between chaperone and substrate. It can be concluded that the vast majority of chaperones do not show a high degree of specificity but recognize elements that signal non-native protein conformation and their substrate range is modulated by the context they function in. However a few chaperones are known that display exquisite specificity of their substrate e.g. mammalian heat shock protein 47 collagen interaction. © 2017 IUBMB Life, 69(9):647-659, 2017.

Anaplastic lymphoma kinase rearrangements in non-small-cell lung cancer: novel applications in diagnostics and treatment

The ALK gene, first identified as an anaplastic large cell lymphoma driver mutation, is dysregulated in nearly 20 different human malignancies, including 3-7% of non-small-cell lung cancers (NSCLC). In NSCLC, ALK commonly fuses with the EML4, forming a constitutively active tyrosine kinase that drives oncogenic progression. Recently, several ALK-inhibiting drugs have been developed that are more effective than standard chemotherapeutic regimens in treating advanced ALK-positive NSCLC. For this reason, molecular diagnostic testing for dysregulated ALK expression is a necessary part of identifying optimal NSCLC treatment options. Here, we review the molecular pathology of ALK-positive NSCLC, ALK molecular diagnostic techniques, ALK-targeted NSCLC treatments, and drug resistance mechanisms to ALK-targeted therapies.

Loss-of-function mutations in co-chaperone BAG3 destabilize small HSPs and cause cardiomyopathy

Defective protein quality control (PQC) systems are implicated in multiple diseases. Molecular chaperones and co-chaperones play a central role in functioning PQC. Constant mechanical and metabolic stress in cardiomyocytes places great demand on the PQC system. Mutation and downregulation of the co-chaperone protein BCL-2-associated athanogene 3 (BAG3) are associated with cardiac myopathy and heart failure, and a BAG3 E455K mutation leads to dilated cardiomyopathy (DCM). However, the role of BAG3 in the heart and the mechanisms by which the E455K mutation leads to DCM remain obscure. Here, we found that cardiac-specific Bag3-KO and E455K-knockin mice developed DCM. Comparable phenotypes in the 2 mutants demonstrated that the E455K mutation resulted in loss of function. Further experiments revealed that the E455K mutation disrupted the interaction between BAG3 and HSP70. In both mutants, decreased levels of small heat shock proteins (sHSPs) were observed, and a subset of proteins required for cardiomyocyte function was enriched in the insoluble fraction. Together, these observations suggest that interaction between BAG3 and HSP70 is essential for BAG3 to stabilize sHSPs and maintain cardiomyocyte protein homeostasis. Our results provide insight into heart failure caused by defects in BAG3 pathways and suggest that increasing BAG3 protein levels may be of therapeutic benefit in heart failure.

Anti-leukemia activity of a Hsp70 inhibitor and its hybrid molecules

In this study we examined the anti-leukemia activity of a small molecule inhibitor of Hsp70 proteins, apoptozole (Az), and hybrids in which it is linked to an inhibitor of either Hsp90 (geldanamycin) or Abl kinase (imatinib). The results of NMR studies revealed that Az associates with an ATPase domain of Hsc70 and thus blocks ATP binding to the protein. Observations made in the cell study indicated that Az treatment promotes leukemia cell death by activating caspase-dependent apoptosis without affecting the caspase-independent apoptotic pathway. Importantly, the hybrids composed of Az and geldanamycin, which have high inhibitory activities towards both Hsp70 and Hsp90, exhibit enhanced anti-leukemia activity relative to the individual inhibitors. However, the Az and imatinib hybrids have weak inhibitory activities towards Hsp70 and Abl, and display lower cytotoxicity against leukemia cells compared to those of the individual constituents. The results of a mechanistic study showed that the active hybrid molecules promote leukemia cell death through a caspase-dependent apoptotic pathway. Taken together, the findings suggest that Hsp70 inhibitors as well as their hybrids can serve as potential anti-leukemia agents.

Mesencephalic astrocyte-derived neurotrophic factor reduces cell apoptosis via upregulating HSP70 in SHSY-5Y cells

Background

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a new candidate growth factor for dopaminergic neurons against endoplasmic reticulum stress (ER stress). HSP70 family, a chaperon like heat shock protein family, was proved to be involved in the MANF induced survival pathway in 6-OHDA treated SHSY-5Y cells. However, the ER stress relative transcriptome, in MANF signaling cascades is still investigated. The involvement of HSP70, a 70kd member of HSP70 family, need further to be verified.

Methods

The cell apoptosis was assayed by MTT, TUNEL staining and western blot of cleaved Caspase-3. The differentially expressed genes in SHSY-5Y cells under different conditions (control, 6-OHDA, 6-OHDA + MANF) were investigated by RNA-seq. Expression of HSP70 was further confirmed by real-time PCR. RNAi knockdown for HSP70 was performed to investigate the role of HSP70 in the MANF signaling pathway.

Results

MANF inhibits 6-OHDA-induced apoptosis in SHSY-5Y cells. Six ER stress relative genes (HSP70, GRP78, xbp-1, ATF-4, ATF-6, MAPK) were found enriched in 6-OHDA + MANF treatment group. HSP70 was the most significantly up-regulated gene under 6-OHDA + MANF treatment in SHSY-5Y cells. RNAi knockdown for HSP70 inhibits the protective effects of MANF against 6-OHDA toxicity in SHSY-5Y cells.

Conclusion

MANF exerts a protective role against 6-OHDA induced apoptosis in SHSY-5Y cells via up-regulating some ER stress genes, including HSP70 family members. The HSP70 expression level plays a key role in MANF-mediated survival pathway.

Exposure to tetrabromobisphenol A induces cellular dysfunction in osteoblastic MC3T3-E1 cells

This study was undertaken to investigate the possible involvement of oxidative stress in tetrabromobisphenol A (TBBPA)-induced toxicity in osteoblastic MC3T3-E1 cells. To examine the potential effect of TBBPA on cultured osteoblastic cells, we measured cell viability, apoptosis, reactive oxygen species (ROS), mitochondrial superoxide, and mitochondrial parameters including adenosine triphosphate (ATP) level, cardiolipin content, cytochrome c release, cyclophilin levels, and differentiation markers in osteoblastic MC3T3-E1 cells. TBBPA exposure for 48 h caused the apoptosis and cytotoxicity of MC3T3-E1 cells. TBBPA also induced ROS and mitochondrial superoxide production in a concentration-dependent manner. These results suggest that TBBPA induces osteoblast apoptosis and ROS production, resulting in bone diseases. Moreover, TBBPA induced cardiolipin peroxidation, cytochrome c release, and decreased ATP levels which induced apoptosis or necrosis. TBBPA decreased the differentiation markers, collagen synthesis, alkaline phosphatase activity, and calcium deposition in cells. Additionally, TBBPA decreased cyclophilin A and B releases. Taken together, these data support the notion that TBBPA inhibits osteoblast function and has detrimental effects on osteoblasts through a mechanism involving oxidative stress and mitochondrial dysfunction.

The chaperone toolbox at the single-molecule level: From clamping to confining

Protein folding is well known to be supervised by a dedicated class of proteins called chaperones. However, the core mode of action of these molecular machines has remained elusive due to several reasons including the promiscuous nature of the interactions between chaperones and their many clients, as well as the dynamics and heterogeneity of chaperone conformations and the folding process itself. While troublesome for traditional bulk techniques, these properties make an excellent case for the use of single-molecule approaches. In this review, we will discuss how force spectroscopy, fluorescence microscopy, FCS, and FRET methods are starting to zoom in on this intriguing and diverse molecular toolbox that is of direct importance for protein quality control in cells, as well as numerous degenerative conditions that depend on it.

Inhibition of HSF1 suppresses the growth of hepatocarcinoma cell lines in vitro and AKT-driven hepatocarcinogenesis in mice

Upregulation of the heat shock transcription factor 1 (HSF1) has been described as a frequent event in many cancer types, but its oncogenic role in hepatocellular carcinoma (HCC) remains poorly delineated. In the present study, we assessed the function(s) of HSF1 in hepatocarcinogenesis via in vitro and in vivo approaches. In particular, we determined the importance of HSF1 on v-Akt murine thymoma viral oncogene homolog (AKT)-induced liver cancer development in mice. We found that knockdown of HSF1 activity via specific siRNA triggered growth restraint by suppressing cell proliferation and inducing massive cell apoptosis in human HCC cell lines. At the molecular level, HSF1 inhibition was accompanied by downregulation of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) cascade and related metabolic pathways. Most importantly, overexpression of a dominant negative form of HSF1 (HSF1dn) in the mouse liver via hydrodynamic gene delivery led to the inhibition of mouse hepatocarcinogenesis driven by overexpression of AKT. In human liver cancer specimens, we detected that HSF1 is progressively induced from human non-tumorous surrounding livers to HCC, reaching the highest expression in the tumors characterized by the poorest outcome (as defined by the length of patients’ survival). In conclusion, HSF1 is an independent prognostic factor in liver cancer and might represent an innovative therapeutic target in HCC subsets characterized by activation of the AKT/mTOR pathway.

Backbone and methyl resonance assignments of the 42 kDa human Hsc70 nucleotide binding domain in the ADP state

Hsc70 is the constitutively expressed mammalian heat shock 70 kDa (Hsp70) cytosolic chaperone. It plays a central role in cellular proteostasis and protein trafficking. Here, we present the backbone and methyl group assignments for the 386-residue nucleotide binding domain of the human protein. This domain controls the chaperone's allostery, binds multiple co-chaperones and is the target of several classes of known chemical Hsp70 inhibitors. The NMR assignments are based on common triple resonance experiments with triple labeled protein, and on several ¹⁵N and ¹³C-resolved 3D NOE experiments with methyl-reprotonated samples. A combination of computer and manual data interpretation was used.

Optimized protocol for soluble prokaryotic expression, purification and structural analysis of human placenta specific-1(PLAC1)

Placenta specific -1 (PLAC1) has been recently introduced as a small membrane-associated protein mainly involved in placental development. Expression of PLAC1 transcript has been documented in almost one hundred cancer cell lines standing for fourteen distinct cancer types. The presence of two disulfide bridges makes difficult to produce functional recombinant PLAC1 in soluble form with high yield. This limitation also complicates the structural studies of PLAC1, which is important for prediction of its physiological roles. To address this issue, we employed an expression matrix consisting of two expression vectors, five different E. coli hosts and five solubilization conditions to optimize production of full and truncated forms of human PLAC1. The recombinant proteins were then characterized using an anti-PLAC1-specific antibody in Western blotting (WB) and enzyme linked immunosorbent assay (ELISA). Structure of full length protein was also investigated using circular dichroism (CD). We demonstrated the combination of Origami™ and pCold expression vector to yield substantial amount of soluble truncated PLAC1 without further need for solubilization step. Full length PLAC1, however, expressed mostly as inclusion bodies with higher yield in Origami™ and Rosetta2. Among solubilization buffers examined, buffer containing Urea 2 M, pH 12 was found to be more effective. Recombinant proteins exhibited excellent reactivity as detected by ELISA and WB. The secondary structure of full length PLAC1 was considered by CD spectroscopy. Taken together, we introduced here a simple, affordable and efficient expression system for soluble PLAC1 production.