Thiolutin inhibits endothelial cell adhesion by perturbing Hsp27 interactions with components of the actin and intermediate filament cytoskeleton

Blocking PSMD14-mediated E2F1/ERK/AKT signaling pathways suppresses the progression of anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is the most aggressive subtype of thyroid cancer with few effective therapeutic strategies. Recent studies have identified the deubiquitinating enzyme (DUB) 26S proteasome non-ATPase regulatory subunit 14 (PSMD14) as a promising therapeutic target for multiple cancers; however, the role of PSMD14 in ATC remains largely unknown. Here, we found that PSMD14 was upregulated in ATC tissues and that its aberrant expression was negatively associated with the overall survival of patients with ATC. Functionally, PSMD14 promotes the proliferation and invasiveness of ATC cells, whereas the depletion of PSMD14 or PSMD14 inhibitor thiolutin (THL) inhibits the growth, invasiveness, and epithelial-mesenchymal transition ((EMT) of ATC cells. In addition, the cell cycle was arrested and apoptosis was increased in PSMD14-depleted ATC or ATC cells treated with THL in vitro. An in vivo assay indicated that THL exerted a potent inhibitory effect on ATC xenografts. Mechanistically, PSMD14 increased E2F1 stabilization by binding to and deubiquitinating E2F1. PSMD14-regulated E2F1 improved the activation of the ERK and AKT signaling pathways, which are instrumental in ATC tumorigenesis and progression. Overall, our findings reveal the oncogenic role of PSMD14 in ATC and provide a promising therapeutic target for the treatment of ATC.

Metabolites Discovery from Streptomyces xanthus: Exploring the Potential of Desert Microorganisms

The Taklamakan Desert is an extreme environment supporting a unique and diverse microbial community with significant potential for exploration. Strain TRM70308T, isolated from desert soil, shares 98.43% 16S rRNA gene sequence similarity with Streptomyces alkaliterrae OF1T. Polyphasic taxonomy confirmed TRM70308T as a novel species, named Streptomyces xanthus. Genomic analysis revealed that only one of the strain's 25 biosynthetic gene clusters (BGCs) formed a cluster of gene families (CGFs) within the MIBiG database, emphasizing its genomics uniqueness. LC-MS/MS and Feature-Based Molecular Networking (FBMN) identified 33 metabolites across various categories, including alkaloids, saponins, benzoic acids, and benzofurans, most of which remain uncharacterized. Further chemical investigation led to the isolation of one novel compound, aconicarpyrazine C, and four known compounds: thiolutin, dibutyl phthalate, bis(2-ethylhexyl) phthalate, and N-acetyltryptamine. Thiolutin exhibited strong activity against five local fungal pathogens that cause plant diseases, with a production yield of 270 mg/L. These results establish a foundation for pilot-scale thiolutin production and its potential development as an antifungal agent for agricultural applications. Our findings highlight deserts as a valuable source of novel actinomycetes and bioactive natural products with immense potential for future research and development.

Thiolutin Alleviates Cardiotoxic Effects of Doxorubicin by Suppressing NLRP3 Inflammasome in the Mouse Model

Doxorubicin (DOX) has a limitation in clinical oncology due to its dose-dependent cardiotoxicity. Thiolutin (THL) can undermine DOX-induced cardiomyocyte injury by inhibiting the NLRP3 inflammasome activation, yet the efficacy of THL in DOX-induced cardiotoxicity (DOXIC) needs to be validated in animal models. DOX-induced mice were treated with THL to evaluate the efficacy of THL. Relative NLRP3 mRNA levels were determined by quantitative PCR. Blood samples were collected from diffuse large B-cell lymphoma (DLBCL) patients with or without DOXIC to validate serum levels of cTnT, IL-1β, CRP, BNP, and IL-18 by enzyme-linked immunosorbent assay. Apoptosis and pyroptosis-related protein levels were analyzed by western blot. Cardiac function and histopathological changes were determined by echocardiography, HE, Masson's, and wheat germ agglutinin staining. In clinical samples, NLRP3 mRNA and/or protein levels were also markedly heightened in peripheral blood mononuclear cells and serum samples from DOXIC patients, along with higher concentrations of IL-18, cTnT, and IL-1β. Importantly, cTnT possessed a positive correlation with NLRP3 mRNA, IL-1β, and IL-18. Moreover, cTnT possessed a positive correlation with NLRP3 mRNA, IL-1β, and IL-18 levels, suggesting a potential link between DOXIC and NLRP3 inflammasome. The outcomes demonstrated that THL reduced LVEF and LVFS, as well as elevated LVESD and LVEDD in DOX-challenged mice, accompanied by elevated serum concentrations of cTnT, CRP, and BNP. In addition, THL attenuated DOX-induced myocardial hypertrophy and cardiac fibrosis in mice, in conjunction with attenuation of DOX-induced upregulation of C-caspase3, Bax, NLRP3, C-caspase-1/Pro-caspase, GSDMD-N/GSDMD, IL-1β, and IL-18 in heart or serum samples. In conclusion, our data supported that THL alleviates the cardiotoxic effects of DOX and suppresses NLRP3 inflammasome in the mouse model, suggesting that THL as a potential drug for DOXIC.

Nestin is a New Partner in Endothelial Colony Forming Cell Angiogenic Potential

Nestin, an intermediate filament protein expressed by progenitor cells, is associated with tissue regeneration. Although nestin expression has been reported in poorly differentiated and newly formed blood vessels, its role in endothelial cells remains unclear. In this study, we investigated the involvement of nestin in the angiogenic properties of endothelial colony-forming cells (ECFCs) derived from human umbilical cord blood. Our results demonstrate that ECFCs express high levels of nestin, and that its inhibition by small interfering RNAs decreased ECFC proliferation, migration in response to SDF-1 and VEGF-A, tubulogenesis, and adhesion on collagen. These effects are associated with modulation of focal adhesion kinase phosphorylation. Furthermore, nestin silencing resulted in reduced revascularization in a mouse hindlimb ischemia model. In conclusion, these findings provide evidence that nestin more than being a structural protein, is an active player in ECFC angiogenic properties.

Phosphorylated heat shock protein 27 improves the bone formation ability of osteoblasts and bone marrow stem cells from patients with adolescent idiopathic scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is a scoliotic deformity of unknown etiology that occurs during adolescent development. Abnormal bone metabolism is closely related to AIS, but the cause is uncertain. Recent studies have shown that heat shock protein 27 (HSP27) and its phosphorylation (pHSP27) play important roles in bone metabolism. However, whether HSP27 and pHSP27 are involved in abnormal bone metabolism in AIS is unclear.

Methods

Osteoblasts (OBs) and bone marrow stem cells (BMSCs) were extracted from the facet joints and bone marrow of AIS patients and controls who underwent posterior spinal fusion surgery. The expression levels of HSP27 and pHSP27, as well as the expression levels of bone formation markers in OBs from AIS patients and controls, were examined by quantitative real-time PCR (qRT-PCR) and Western blotting. The mineralization ability of OBs from AIS patients and controls was analyzed by alizarin red staining after osteogenic differentiation. Heat shock and thiolutin were used to increase the levels of pHSP27 in OBs, and the levels of bone formation markers were also investigated. In addition, the levels of pHSP27 and the bone formation ability of BMSCs from AIS patients and controls were investigated after heat shock treatment.

Results

Lower pHSP27 levels and impaired osteogenic differentiation abilities were observed in the OBs of AIS patients than in those of controls. Thiolutin increased HSP27 phosphorylation and increased the mRNA levels of SPP1 and ALPL in OBs from AIS patients. Heat shock treatment increased SPP1 and HSP27 mRNA expression, pHSP27 levels, OCN expression, and mineralization ability of both OBs and BMSCs from AIS patients.

Conclusion

Heat shock treatment and thiolutin can increase the levels of pHSP27 and further promote the bone formation of OBs and BMSCs from AIS patients. Therefore, decreased pHSP27 levels may be associated with abnormal bone metabolism in AIS patients.

Thiolutin attenuates ischemic stroke injury via inhibition of NLRP3 inflammasome: an in vitro and in vivo study

A recent study confirmed that thiolutin is effective in the treatment of nucleotide-binding domain-like receptor protein 3 (NLRP3)-related inflammatory diseases. Nevertheless, whether thiolutin (THL) is involved in the regulation of NLRP3 inflammasome in ischemic stroke is not known. The murine neuronal cell oxygen-glucose deprivation (OGD) model was first established, and then different concentrations (25 nM and 50 nM) of THL were administered for 48 h incubation, respectively. Subsequently, cell viability and toxicity, and the levels of intracellular inflammatory factors interleukin-1β (IL-1β), interleukin-18 (IL-18), oxidative stress factors superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and malondialdehyde (MDA), and NLRP3 inflammasome activation-related proteins pro-caspase, caspase-1, apoptosis-associated speck like-protein (ASC) and NLRP3 were examined, respectively. We further established the mouse middle cerebral artery occlusion (MCAO) model to evaluate the therapeutic effects of THL on cerebral infarction like behaviors in mice and the preventive effects on NLRP3 inflammasome activation in vivo. Cell cytotoxic, and the levels of inflammatory factors and oxidative stress were conspicuously increased, and NLRP3 inflammasome was materially activated in the OGD-induced cell model and MCAO-established mouse model, which were partially countered by THL treatment. Besides, intraperitoneal injection of THL could prominently reduce the cerebral infarct volume and neuromotor deficit scores in MCAO mice. The present study confirmed that THL attenuated neuronal and cerebral inflammatory injury caused by OGD and MCAO models in mice through restraining NLRP3 inflammasome activation in vitro and in vivo.

The Role of Heat Shock Protein 27 in Carcinogenesis and Treatment of Colorectal Cancer

The incidence of colorectal cancer (CRC) has significantly increased in recent decades, which has made this disease an important global health issue. Despite many efforts, there is no useful prognostic or diagnostic biomarker for CRC. Heat shock protein 27 (Hsp27) is one of the most studied members of the Hsp family. It has attracted particular attention in CRC pathogenesis since it is involved in fundamental cell functions for cell survival. Evidence shows that Hsp27 plays important role in CRC progression and metastasis. Hsp27 overexpression has been observed in CRC and is suggested to be associated with CRC's poor prognosis. In the present review, we focus on the current knowledge of the role of Hsp27 in CRC carcinogenesis and the underlying mechanisms. In addition, we discuss the value of targeting Hsp27 in CRC treatment.

Natural Products from Tongan Marine Organisms

The islands of the South Pacific Ocean have been in the limelight for natural product biodiscovery, due to their unique and pristine tropical waters and environment. The Kingdom of Tonga is an archipelago in the central Indo-Pacific Ocean, consisting of 176 islands, 36 of which are inhabited, flourishing with a rich diversity of flora and fauna. Many unique natural products with interesting bioactivities have been reported from Indo-Pacific marine sponges and other invertebrate phyla; however, there have not been any reviews published to date specifically regarding natural products from Tongan marine organisms. This review covers both known and new/novel Marine Natural Products (MNPs) and their biological activities reported from organisms collected within Tongan territorial waters up to December 2020, and includes 109 MNPs in total, the majority from the phylum Porifera. The significant biological activity of these metabolites was dominated by cytotoxicity and, by reviewing these natural products, it is apparent that the bulk of the new and interesting biologically active compounds were from organisms collected from one particular island, emphasizing the geographic variability in the chemistry between these organisms collected at different locations.

Pharmacological targeting of NLRP3 deubiquitination for treatment of NLRP3-associated inflammatory diseases

Pharmacologically inhibiting nucleotide-binding domain and leucine-rich repeat-containing (NLR) family, pyrin domain-containing protein 3 (NLRP3) inflammasome activation results in potent therapeutic effects in a wide variety of preclinical inflammatory disease models. NLRP3 deubiquitination is essential for efficient NLRP3 inflammasome activity, but it remains unclear whether this process can be harnessed for therapeutic benefit. Here, we show that thiolutin (THL), an inhibitor of the JAB1/MPN/Mov34 (JAMM) domain-containing metalloprotease, blocks NLRP3 inflammasome activation by canonical, noncanonical, alternative, and transcription-independent pathways at nanomolar concentrations. In addition, THL potently inhibited the activation of multiple NLRP3 mutants linked with cryopyrin-associated periodic syndromes (CAPS). Treatment with THL alleviated NLRP3-related diseases in mouse models of lipopolysaccharide-induced sepsis, monosodium urate-induced peritonitis, experimental autoimmune encephalomyelitis, CAPS, and methionine-choline-deficient diet-induced nonalcoholic fatty liver disease. Mechanistic studies revealed that THL inhibits the BRCC3-containing isopeptidase complex (BRISC)-mediated NLRP3 deubiquitination and activation. In addition, we show that holomycin, a natural methyl derivative of THL, displays an even higher inhibitory activity against NLRP3 inflammasome than THL. Our study validates that posttranslational modification of NLRP3 can be pharmacologically targeted to prevent or treat NLRP3-associated inflammatory diseases. Future clinical development of derivatives of THL may provide new therapies for NLRP3-related diseases.

The PSMD14 inhibitor Thiolutin as a novel therapeutic approach for esophageal squamous cell carcinoma through facilitating SNAIL degradation

Metastasis and chemoresistance are major causes of poor prognosis in patients with esophageal squamous cell carcinoma (ESCC), manipulated by multiple factors including deubiquitinating enzyme (DUB). DUB PSMD14 is reported to be a promising therapeutic target in various cancers. Here, we explored the antitumor activity of Thiolutin (THL), the PSMD14 inhibitor, as a new therapy strategy in ESCC.

Methods: Through 4-NQO-induced murine ESCC model, we investigated the expression of PSMD14 in esophageal tumorigenesis. Ubiquitin-AMC assay was performed to evaluate DUB activity of PSMD14 with THL treatment. The effect of THL on epithelial-to-mesenchymal transition (EMT), invasion, stemness and chemosensitivity was detected by using in vitro and in vivo experiments. Immunoprecipitation and in vivo ubiquitination assay were conducted to examine whether THL could impair the deubiquitination and stability of SNAIL regulated by PSMD14.

Results: Compared with normal esophageal epithelium, PSMD14 was upregulated in 4-NQO-induced murine esophageal epithelium dysplasia and ESCC tissues. THL could significantly weaken DUB activity of PSMD14. Furthermore, the results of in vitro and in vivo assays showed that THL efficiently suppressed motility and stemness and increased sensitivity to cisplatin in ESCC. Mechanically, THL impaired the interaction between PSMD14 and SNAIL, then promoted the ubiquitination and degradation of SNAIL to inhibit EMT which plays a crucial role in ESCC metastasis, stemness and chemosensitivity. TCGA database analysis revealed that high concomitant PSMD14/SNAIL expression predicted shorter overall survival in esophageal cancer.

Conclusion: Our findings demonstrate for the first time that suppression of PSMD14/SNAIL axis by THL could be a novel and promising therapeutic approach for ESCC clinical therapy.

Blockade of deubiquitinating enzyme PSMD14 overcomes chemoresistance in head and neck squamous cell carcinoma by antagonizing E2F1/Akt/SOX2-mediated stemness

Increasing evidence reveals a close relationship between deubiquitinating enzymes (DUBs) and cancer progression. In this study, we attempted to identify the roles and mechanisms of critical DUBs in head and neck squamous cell carcinoma (HNSCC).

Methods: Bioinformatics analysis was performed to screen differentially expressed novel DUBs in HNSCC. Immunohistochemistry assay was used to measure the expression of DUB PSMD14 in HNSCC specimens and adjacent normal tissues. The level of PSMD14 in HNSCC tumorigenesis was investigated using a 4-NQO-induced murine HNSCC model. The function of PSMD14 was determined through loss-of-function assays. Chromatin immunoprecipitation, immunoprecipitation and in vivo ubiquitination assay were conducted to explore the potential mechanism of PSMD14. The anti-tumor activity of PSMD14 inhibitor Thiolutin was assessed by in vitro and in vivo experiments.

Results: We identified PSMD14 as one of significantly upregulated DUBs in HNSCC tissues. Aberrant expression of PSMD14 was associated with tumorigenesis and malignant progression of HNSCC and further indicated poor prognosis. The results of in vitro and in vivo experiments demonstrated PSMD14 depletion significantly undermined HNSCC growth, chemoresistance and stemness. Mechanically, PSMD14 inhibited the ubiquitination and degradation of E2F1 to improve the activation of Akt pathway and the transcription of SOX2. Furthermore, PSMD14 inhibitor Thiolutin exhibited a potent anti-tumor effect on HNSCC in vivo and in vitro by impairing DUB activity of PSMD14.

Conclusion: Our findings demonstrate the role and mechanism of PSMD14 in HNSCC, and provide a novel and promising target for diagnosis and clinical therapy of HNSCC.

A new dithiolopyrrolone antibiotic triggered by a long fermentation of Saccharothrix algeriensis NRRL B-24137 in sorbic acid-amended medium

Saccharothrix algeriensis NRRL B-24137 is an actinobacterium isolated from Algerian Saharan soil. It produces bioactive compounds belonging to the dithiolopyrrolone class of antibiotics, which are characterized by the possession of a unique pyrrolinonodithiole nucleus. Dithiolopyrrolones are known for their strong antibacterial and antifungal activities. This class of antibiotics generated great interest after the discovery of their anticancer properties. In this study, an antibiotic named PR11, produced after a long bacterial fermentation (11 days) in sorbic acid-containing culture broth, was characterized as a new dithiolopyrrolone derivative. After HPLC analysis and purification, the chemical structure of this antibiotic was determined by ¹ H- and ¹³ C-nuclear magnetic resonance, mass and UV-visible data. PR11 was thus characterized as an iso-hexanoyl-pyrrothine, a novel dithiolopyrrolone derivative. The minimum inhibitory concentrations of the new induced antibiotic were determined against several pathogenic micro-organisms. A moderate to strong activity was noted against all Gram-positive bacteria, filamentous fungi and yeasts tested. SIGNIFICANCE AND IMPACT OF THE STUDY: Given the strong activities of dithiolopyrrolones against diverse prokaryotic and eukaryotic micro-organisms including potent selective-anticancer activity, the discovery of new-related derivatives draw continuous attention for therapeutic research. Depending on nature and concentration of added precursor, Saccharothrix algeriensis NRRL B-24137 produce several dithiolopyrrolone coumpounds. In this study, sorbic acid addition combined to long fermentation duration was shown to induce the biosynthesis of a novel dithiolopyrrolone derivative. After purification and full spectroscopic and spectrometric study, the compound was characterized as iso-hexanoyl-pyrrothine. In the future investigation for novel dithiolopyrrolone discovery, fermentation duration should be regarded as a key parameter as well.

Effective biosynthesis of benzoyl-pyrrothine dithiolopyrrolone antibiotic by cinnamic acid-precursor addition in culture of Saccharothrix algeriensis NRRL B-24137

Dithiolopyrrolone antibiotics, produced by several micro-organisms, are known for their strong antimicrobial and antitumor activities. Among of this micro-organisms, Saccharothrix algeriensis NRRL B-24137, a rare actinobacterium, has the ability to produce several dithiolopyrrolones derivatives depending on precursors added in the culture medium. After 10 days of strain fermentation on semi-synthetic medium supplemented with cinnamic acid and HPLC purification, biosynthesis of benzoyl-pyrrothine dithiolopyrrolone was evidenced through complete spectroscopic (UV-visible and 1H and 13C NMR) and spectrometric (electron impact mass spectrum) analyses. The pure molecule showed appreciable minimum inhibitory concentration values against several Gram-positive bacteria and filamentous fungi. SIGNIFICANCE AND IMPACT OF THE STUDY: Dithiolopyrrolone antibiotics, known for their strong antimicrobial activities, gained greater interest after the discovery of their antitumor properties. Depending on precursors added, Saccharothrix algeriensis NRRL B-24137 has the ability to produce several dithiolopyrrolones derivatives. Since biological activities of dithiolopyrrolones are related to their variable structure, discover of new natural analogues to be therapeutically explored remains a significant framework of research. In this study, a new dithiolopyrrolone derivative was purified from the fermentation broth of S. algeriensis NRRL B-24137. This new antibiotic, characterized as benzoyl-pyrrothine dithiolopyrrolone, was induced by adding cinnamic acid, as precursor, to a semi-synthetic medium.

Identification and characterization of Streptomyces flavogriseus NJ-4 as a novel producer of actinomycin D and holomycin

This paper is the first public report that Streptomyces flavogriseus can produce both actinomycin D and holomycin. The actinomycete strain NJ-4 isolated from the soil of Nanjing Agricultural University was identified as S. flavogriseus. This S. flavogriseus strain was found for the first time to produce two antimicrobial compounds that were identified as actinomycin D and holomycin. GS medium, CS medium and GSS medium were used for the production experiments. All three media supported the production of actinomycin D, while holomycin was detected only in GS medium and was undetectable by HPLC in the CS and GSS media. The antimicrobial activity against B. pumilus, S. aureus, Escherichia coli, F. moniliforme, F. graminearum and A. niger was tested using the agar well diffusion method. Actinomycin D exhibited strong antagonistic activities against all the indicator strains. Holomycin exhibited strong antagonistic activities against B. pumilus, S. aureus and E. coli and had antifungal activity against F. moniliforme and F. graminearum but had no antifungal activity against A. niger. The cell viability was determined using an MTT assay. Holomycin exhibited cytotoxic activity against A549 lung cancer cells, BGC823 gastric cancer cells and HepG2 hepatocellular carcinoma cells. The yield of actinomycin D from S. flavogriseus NJ-4 was 960 mg/l. S. flavogriseus NJ-4 exhibits a distinct capability and has the industrial potential to produce considerable yields of actinomycin D under unoptimized conditions.

Thiolutin is a zinc chelator that inhibits the Rpn11 and other JAMM metalloproteases

Thiolutin is a disulfide-containing antibiotic and anti-angiogenic compound produced by Streptomyces. Its biological targets are not known. We show that reduced thiolutin is a zinc chelator that inhibits the JAB1/MPN/Mov34 (JAMM) domain-containing metalloprotease Rpn11, a deubiquitinating enzyme of the 19S proteasome. Thiolutin also inhibits the JAMM metalloproteases Csn5, the deneddylase of the COP9 signalosome; AMSH, which regulates ubiquitin-dependent sorting of cell-surface receptors; and BRCC36, a K63-specific deubiquitinase of the BRCC36-containing isopeptidase complex and the BRCA1-BRCA2-containing complex. We provide evidence that other dithiolopyrrolones also function as inhibitors of JAMM metalloproteases.

Identification of an unusual type II thioesterase in the dithiolopyrrolone antibiotics biosynthetic pathway

Dithiolopyrrolone group antibiotics characterized by an electronically unique dithiolopyrrolone heterobicyclic core are known for their antibacterial, antifungal, insecticidal and antitumor activities. Recently the biosynthetic gene clusters for two dithiolopyrrolone compounds, holomycin and thiomarinol, have been identified respectively in different bacterial species. Here, we report a novel dithiolopyrrolone biosynthetic gene cluster (aut) isolated from Streptomyces thioluteus DSM 40027 which produces two pyrrothine derivatives, aureothricin and thiolutin. By comparison with other characterized dithiolopyrrolone clusters, eight genes in the aut cluster were verified to be responsible for the assembly of dithiolopyrrolone core. The aut cluster was further confirmed by heterologous expression and in-frame gene deletion experiments. Intriguingly, we found that the heterogenetic thioesterase HlmK derived from the holomycin (hlm) gene cluster in Streptomyces clavuligerus significantly improved heterologous biosynthesis of dithiolopyrrolones in Streptomyces albus through coexpression with the aut cluster. In the previous studies, HlmK was considered invalid because it has a Ser to Gly point mutation within the canonical Ser-His-Asp catalytic triad of thioesterases. However, gene inactivation and complementation experiments in our study unequivocally demonstrated that HlmK is an active distinctive type II thioesterase that plays a beneficial role in dithiolopyrrolone biosynthesis.

Proteomic Analysis Revealed the Important Role of Vimentin in Human Cervical Carcinoma HeLa Cells Treated With Gambogic Acid

Gambogic acid (GA) is an anticancer agent in phase IIb clinical trial in China. In HeLa cells, GA inhibited cell proliferation, induced cell cycle arrest at G2/M phase and apoptosis, as showed by results of MTT assay and flow cytometric analysis. Possible target-related proteins of GA were searched using comparative proteomic analysis (2-DE) and nine proteins at early (3 h) stage together with nine proteins at late (24 h) stage were found. Vimentin was the only target-related protein found at both early and late stage. Results of both 2-DE analysis and Western blotting assay suggested cleavage of vimentin induced by GA. MS/MS analysis of cleaved vimentin peptides indicated possible cleavage sites of vimentin at or near ser51 and glu425. Results of targeted proteomic analysis showed that GA induced change in phosphorylation state of the vimentin head domain (aa51-64). Caspase inhibitors could not abrogate GA-induced cleavage of vimentin. Over-expression of vimentin ameliorated cytotoxicity of GA in HeLa cells. The GA-activated signal transduction, from p38 MAPK, heat shock protein 27 (HSP27), vimentin, dysfunction of cytoskeleton, to cell death, was predicted and then confirmed. Results of animal study showed that GA treatment inhibited tumor growth in HeLa tumor-bearing mice and cleavage of vimentin could be observed in tumor xenografts of GA-treated animals. Results of immunohistochemical staining also showed down-regulated vimentin level in tumor xenografts of GA-treated animals. Furthermore, compared with cytotoxicity of GA in HeLa cells, cytotoxicity of GA in MCF-7 cells with low level of vimentin was weaker whereas cytotoxicity of GA in MG-63 cells with high level of vimentin was stronger. These results indicated the important role of vimentin in the cytotoxicity of GA. The effects of GA on vimentin and other epithelial-to-mesenchymal transition (EMT) markers provided suggestion for better usage of GA in clinic.

Dithiolopyrrolones: biosynthesis, synthesis, and activity of a unique class of disulfide-containing antibiotics

Covering: up to 2014. Dithiolopyrrolone (DTP) group antibiotics were first isolated in the early half of the 20th century, but only recently has research been reawakened by insights gained from the synthesis and biosynthesis of this structurally intriguing class of molecules. DTPs are characterized by an electronically unique bicyclic structure, which contains a compact disulfide bridge between two ene-thiols. Points of diversity within the compound class occur outside of the bicyclic core, at the two amide nitrogens. Such modifications distinguish three of the most well studied members of the class, holomycin, thiolutin, and aureothricin; the DTP core has also more recently been identified in the marine antibiotic thiomarinol, in which it is linked to a marinolic acid moiety, analog of the FDA-approved topical antibiotic Bactroban® (GlaxoSmithKline). Dithiolopyrrolones exhibit relatively broad-spectrum antibiotic activity against many Gram-positive and Gram-negative bacteria, as well as strains of Mycobacterium tuberculosis. Additionally, they have been shown to exhibit potent and selective anti-cancer activity. Despite this promising profile, there is still much unknown about the mechanisms of action for DTPs. Early reports suggested that they inhibit yeast growth at the level of transcription and that this effect is largely responsible for their distinctive microbial static properties; a similar mechanism is supported in bacteria. Elucidation of biosynthetic pathways for holomycin in Streptomyces clavuligerus and Yersinia ruckeri and thiomarinol in Alteromonas rava sp. nov. SANK 73390, have contributed evidence suggesting that multiple mechanisms may be operative in the activity of these compounds. This review will comprehensively cover the history and development of dithiolopyrrolones with particular emphasis on the biosynthesis, synthesis, biological activity and mechanism of action.

Identification of two putative acyltransferase genes potentially implicated in dithiolopyrrolone biosyntheses in Saccharothrix algeriensis NRRL B-24137

The dithiolopyrrolone class of antibiotics has been known to display bacteriostatic activity against both Gram-positive and Gram-negative bacteria and exert other biological activities. Acyltransferase activities are proposed to be responsible for the structural diversity of dithiolopyrrolones produced by Saccharothrix algeriensis NRRL B-24137. Moreover, two activities, pyrrothine N-acetyltransferase and pyrrothine N-benzoyltransferase, are reported to catalyze the formation, respectively, to thiolutin and benzoyl-pyrrothine (BEP) in this bacterium. In this study, two genes encoding two putative acyltransferases were identified in S. algeriensis. The first one, actA, was identified by bioinformatic analysis and by analogy to an acetyltransferase, hlmA, identified in holomycin biosynthetic gene cluster in Streptomyces clavuligerus. The second was identified by purification of both enzymes from the bacterial biomass which provided a semipurified extract. The microsequencing of tryptic peptides from the final protein preparation yielded sequences of eight different fragments, two of them encoded by one gene, actB, in S. algeriensis genome bank. The alignment of actB against the GenBank database revealed significant homology to acyltransferase family. Differential expression of these genes, actA and actB, was then investigated in three different media: (i) semisynthetic medium (SSM), which promotes the production of thiolutin; (ii) SSM supplemented by 1.25 mM benzoic acid (SSM + BA), which promotes the production of both thiolutin and BEP; and (iii) tryptic soy broth (TSB) in which no dithiolopyrrolone derivatives were detected.

Dithiolopyrrolone natural products: isolation, synthesis and biosynthesis

Dithiolopyrrolones are a class of antibiotics that possess the unique pyrrolinonodithiole (4H-[1,2] dithiolo [4,3-b] pyrrol-5-one) skeleton linked to two variable acyl groups. To date, there are approximately 30 naturally occurring dithiolopyrrolone compounds, including holomycin, thiolutin, and aureothricin, and more recently thiomarinols, a unique class of hybrid marine bacterial natural products containing a dithiolopyrrolone framework linked by an amide bridge with an 8-hydroxyoctanoyl chain linked to a monic acid. Generally, dithiolopyrrolone antibiotics have broad-spectrum antibacterial activity against various microorganisms, including Gram-positive and Gram-negative bacteria, and even parasites. Holomycin appeared to be active against rifamycin-resistant bacteria and also inhibit the growth of the clinical pathogen methicillin-resistant Staphylococcus aureus N315. Its mode of action is believed to inhibit RNA synthesis although the exact mechanism has yet to be established in vitro. A recent work demonstrated that the fish pathogen Yersinia ruckeri employs an RNA methyltransferase for self-resistance during the holomycin production. Moreover, some dithiolopyrrolone derivatives have demonstrated promising antitumor activities. The biosynthetic gene clusters of holomycin have recently been identified in S. clavuligerus and characterized biochemically and genetically. The biosynthetic gene cluster of thiomarinol was also identified from the marine bacterium Pseudoalteromonas sp. SANK 73390, which was uniquely encoded by two independent pathways for pseudomonic acid and pyrrothine in a novel plasmid. The aim of this review is to give an overview about the isolations, characterizations, synthesis, biosynthesis, bioactivities and mode of action of this unique family of dithiolopyrrolone natural products, focusing on the period from 1940s until now.

Cell stress promotes the association of phosphorylated HspB1 with F-actin

Previous studies have suggested that the small heat shock protein, HspB1, has a direct influence on the dynamics of cytoskeletal elements, in particular, filamentous actin (F-actin) polymerization. In this study we have assessed the influence of HspB1 phosphorylation on its interaction(s) with F-actin. We first determined the distribution of endogenous non-phosphorylated HspB1, phosphorylated HspB1 and F-actin in neuroendocrine PC12 cells by immunocytochemistry and confocal microscopy. We then investigated a potential direct interaction between HspB1 with F-actin by precipitating F-actin directly with biotinylated phalloidin followed by Western analyses; the reverse immunoprecipitation of HspB1 was also carried out. The phosphorylation influence of HspB1 in this interaction was investigated by using pharmacologic inhibition of p38 MAPK. In control cells, HspB1 interacts with F-actin as a predominantly non-phosphorylated protein, but subsequent to stress there is a redistribution of HspB1 to the cytoskeletal fraction and a significantly increased association of pHspB1 with F-actin. Our data demonstrate HspB1 is found in a complex with F-actin both in phosphorylated and non-phosphorylated forms, with an increased association of pHspB1 with F-actin after heat stress. Overall, our study combines both cellular and biochemical approaches to show cellular localization and direct demonstration of an interaction between endogenous HspB1 and F-actin using methodolgy that specifically isolates F-actin.

Mitochondrial proteomic analysis of cisplatin resistance in ovarian cancer

Epithelial ovarian cancer (EOC) is the leading cause of death among women with gynecologic malignancies and accounts for approximately 6% of cancer deaths among women. Cisplatin and its analogues form the backbone of the most active chemotherapy regimens in advanced EOC; however, development of platinum resistance is common and typically marks a transition in which curing the patient is no longer possible. An emerging theme in many cancers is that mitochondrial dysfunction contributes to an aggressive carcinogenic phenotype. We hypothesized that changes in the mitochondrial proteome are required to support development of cisplatin resistance in human EOC. To investigate this hypothesis, an organellar proteomics approach was utilized to quantify alterations in protein abundance in mitochondria enriched from isogenic cisplatin-sensitive (A2780) and -resistant (A2780-CP20) human EOC cells. Protein isolates from mitochondria-enriched fractions were analyzed by high resolution liquid chromatography-tandem mass spectrometry (LC-MS/MS), and relative abundance of identified proteins was quantified by spectral counting. Pathway analyses revealed significant increases in notch signaling pathways, cell survival, and alternate apoptotic pathways in the A2780-CP20 subtype. Among the alterations identified in the mitochondrial proteomic composition in cisplatin-resistant EOC cells, activated leukocyte cell adhesion molecule (AKAP12) and A kinase anchoring protein 12 (AKAP12) were elevated, while nestin was diminished in the mitochondrial fraction of A2780-CP20 relative to A2780. This was verified by immunoblot analysis. These results confirm that important changes in the mitochondrial proteome, many of which promote evasion of apoptosis and tumor invasiveness and metastasis, are present in cisplatin-resistant EOC.

Charcot-Marie-Tooth disease and intracellular traffic

Mutations of genes whose primary function is the regulation of membrane traffic are increasingly being identified as the underlying causes of various important human disorders. Intriguingly, mutations in ubiquitously expressed membrane traffic genes often lead to cell type- or organ-specific disorders. This is particularly true for neuronal diseases, identifying the nervous system as the most sensitive tissue to alterations of membrane traffic. Charcot-Marie-Tooth (CMT) disease is one of the most common inherited peripheral neuropathies. It is also known as hereditary motor and sensory neuropathy (HMSN), which comprises a group of disorders specifically affecting peripheral nerves. This peripheral neuropathy, highly heterogeneous both clinically and genetically, is characterized by a slowly progressive degeneration of the muscle of the foot, lower leg, hand and forearm, accompanied by sensory loss in the toes, fingers and limbs. More than 30 genes have been identified as targets of mutations that cause CMT neuropathy. A number of these genes encode proteins directly or indirectly involved in the regulation of intracellular traffic. Indeed, the list of genes linked to CMT disease includes genes important for vesicle formation, phosphoinositide metabolism, lysosomal degradation, mitochondrial fission and fusion, and also genes encoding endosomal and cytoskeletal proteins. This review focuses on the link between intracellular transport and CMT disease, highlighting the molecular mechanisms that underlie the different forms of this peripheral neuropathy and discussing the pathophysiological impact of membrane transport genetic defects as well as possible future ways to counteract these defects.

IGF2BP1 promotes cell migration by regulating MK5 and PTEN signaling

In primary neurons, the oncofetal RNA-binding protein IGF2BP1 (IGF2 mRNA-binding protein 1) controls spatially restricted β-actin (ACTB) mRNA translation and modulates growth cone guidance. In cultured tumor-derived cells, IGF2BP1 was shown to regulate the formation of lamellipodia and invadopodia. However, how and via which target mRNAs IGF2BP1 controls the motility of tumor-derived cells has remained elusive. In this study, we reveal that IGF2BP1 promotes the velocity and directionality of tumor-derived cell migration by determining the cytoplasmic fate of two novel target mRNAs: MAPK4 and PTEN. Inhibition of MAPK4 mRNA translation by IGF2BP1 antagonizes MK5 activation and prevents phosphorylation of HSP27, which sequesters actin monomers available for F-actin polymerization. Consequently, HSP27-ACTB association is reduced, mobilizing cellular G-actin for polymerization in order to promote the velocity of cell migration. At the same time, stabilization of the PTEN mRNA by IGF2BP1 enhances PTEN expression and antagonizes PIP(3)-directed signaling. This enforces the directionality of cell migration in a RAC1-dependent manner by preventing additional lamellipodia from forming and sustaining cell polarization intrinsically. IGF2BP1 thus promotes the velocity and persistence of tumor cell migration by controlling the expression of signaling proteins. This fine-tunes and connects intracellular signaling networks in order to enhance actin dynamics and cell polarization.

Large potentials of small heat shock proteins

Modern classification of the family of human small heat shock proteins (the so-called HSPB) is presented, and the structure and properties of three members of this family are analyzed in detail. Ubiquitously expressed HSPB1 (HSP27) is involved in the control of protein folding and, when mutated, plays a significant role in the development of certain neurodegenerative disorders. HSPB1 directly or indirectly participates in the regulation of apoptosis, protects the cell against oxidative stress, and is involved in the regulation of the cytoskeleton. HSPB6 (HSP20) also possesses chaperone-like activity, is involved in regulation of smooth muscle contraction, has pronounced cardioprotective activity, and seems to participate in insulin-dependent regulation of muscle metabolism. HSPB8 (HSP22) prevents accumulation of aggregated proteins in the cell and participates in the regulation of proteolysis of unfolded proteins. HSPB8 also seems to be directly or indirectly involved in regulation of apoptosis and carcinogenesis, contributes to cardiac cell hypertrophy and survival and, when mutated, might be involved in development of neurodegenerative diseases. All small heat shock proteins play important "housekeeping" roles and regulate many vital processes; therefore, they are considered as attractive therapeutic targets.

Distension of the uterus induces HspB1 expression in rat uterine smooth muscle

The uterine musculature, or myometrium, demonstrates tremendous plasticity during pregnancy under the influences of the endocrine environment and mechanical stresses. Expression of the small stress protein heat shock protein B1 (HspB1) has been reported to increase dramatically during late pregnancy, a period marked by myometrial hypertrophy caused by fetal growth-induced uterine distension. Thus, using unilaterally pregnant rat models and ovariectomized nonpregnant rats with uteri containing laminaria tents to induce uterine distension, we examined the effect of uterine distension on myometrial HspB1 expression. In unilaterally pregnant rats, HspB1 mRNA and Ser15-phosphorylated HspB1 (pSer15 HspB1) protein expression were significantly elevated in distended gravid uterine horns at days 19 and 23 (labor) of gestation compared with nongravid horns. Similarly, pSer15 HspB1 protein in situ was only readily detectable in the distended horns compared with the nongravid horns at days 19 and 23; however, pSer15 HspB1 was primarily detectable in situ at day 19 in membrane-associated regions, while it had primarily a cytoplasmic localization in myometrial cells at day 23. HspB1 mRNA and pSer15 HspB1 protein expression were also markedly increased in ovariectomized nonpregnant rat myometrium distended for 24 h with laminaria tents compared with empty horns. Therefore, uterine distension plays a major role in the stimulation of myometrial HspB1 expression, and increased expression of this small stress protein could be a mechanoadaptive response to the increasing uterine distension that occurs during pregnancy.

A novel sialyltransferase inhibitor suppresses FAK/paxillin signaling and cancer angiogenesis and metastasis pathways

Increased sialyltransferase (ST) activity promotes cancer cell metastasis, and overexpression of cell surface sialic acid correlates with poor prognosis in cancer patients. To seek therapies targeting metastasis for cancer treatment, we developed a novel ST inhibitor, Lith-O-Asp, and investigated its antimetastatic and antiangiogenic effects and mechanisms. We found that cells treated with Lith-O-Asp showed a reduction of activity on various ST enzymes by in vitro and cell-based activity analyses. Lith-O-Asp inhibited migration and invasion abilities in various cancer cell lines and showed inhibitory effect on the angiogenic activity of human umbilical vein endothelial cells. Indeed, Lith-O-Asp treatment consequently delayed cancer cell metastasis in experimental and spontaneous metastasis assays in animal models. Importantly, Lith-O-Asp decreased the sialic acid modification of integrin-β1 and inhibited the expression of phospho-FAK, phospho-paxillin, and the matrix metalloprotease (MMP) 2 and MMP9. Lith-O-Asp attenuated the Rho GTPase activity leading to actin dynamic impairment. In addition, 2DE-MS/MS and immunoblotting analyses showed that Lith-O-Asp altered the protein expression level and phosphorylation status of various proteins involved in crucial metastasis and angiogenesis pathways such as vimentin and ribonuclease/angiogenin inhibitor RNH1. Furthermore, Lith-O-Asp treatment significantly inhibited the invasive ability exerted by ectopic overexpression of various ST enzymes catalyzing α-2,6- or α-2,3-sialylation. Our results provide compelling evidence that the potential pan-ST inhibitor, Lith-O-Asp, suppressed cancer cell metastasis likely by inhibiting FAK/paxillin signaling and expressing antiangiogenesis factors. Lith-O-Asp is worthy for further testing as a novel antimetastasis drug for cancer treatment.

Truncation attenuates molecular chaperoning and apoptosis inhibition by p26, a small heat shock protein from Artemia franciscana

The small heat shock proteins (sHSPs), which prevent irreversible protein denaturation and inhibit apoptosis, consist of an amino-terminus, the canonical α-crystallin domain, and a carboxy-terminal extension. It remains difficult, however, to define sHSP structure-function relationships and with this in mind p26, an sHSP from the crustacean Artemia franciscana, was truncated by deletion mutagenesis. Wild-type p26 cDNA and three truncated variants inserted into the eukaryotic expression vector pcDNA3.1/HisC were used to generate stably transfected 293H cells. p26 shielded transfected cells against death upon exposure to heat and oxidative stress. Truncation reduced chaperone activity, with cells synthesizing the p26 α-crystallin domain being the least resistant. Wild-type p26 inhibited apoptosis in transfected cells, with protection against oxidation-generated apoptosis being more effective than that against heat-induced apoptosis. Truncation reduced p26 apoptotic inhibitory activity, with the α-crystallin domain again being the least effective. The results show that a crustacean sHSP functions effectively in mammalian cells, demonstrating interchangeability of these proteins between distantly related organisms and indicating similarities in their mechanisms of action. Moreover, maximal activity was observed for full-length p26, indicating that structural elements required for chaperone activity and apoptosis inhibition reside throughout the protein.

Proteasome inhibition induces hsp30 and hsp70 gene expression as well as the acquisition of thermotolerance in Xenopus laevis A6 cells

Previous studies have shown that inhibiting the activity of the proteasome leads to the accumulation of damaged or unfolded proteins within the cell. In this study, we report that proteasome inhibitors, lactacystin and carbobenzoxy-L-leucyl-L-leucyl-L-leucinal (MG132), induced the accumulation of ubiquitinated proteins as well as a dose- and time-dependent increase in the relative levels of heat shock protein (HSP)30 and HSP70 and their respective mRNAs in Xenopus laevis A6 kidney epithelial cells. In A6 cells recovering from MG132 exposure, HSP30 and HSP70 levels were still elevated after 24 h but decreased substantially after 48 h. The activation of heat shock factor 1 (HSF1) may be involved in MG132-induced hsp gene expression in A6 cells since KNK437, a HSF1 inhibitor, repressed the accumulation of HSP30 and HSP70. Exposing A6 cells to simultaneous MG132 and mild heat shock enhanced the accumulation of HSP30 and HSP70 to a much greater extent than with each stressor alone. Immunocytochemical studies determined that HSP30 was localized primarily in the cytoplasm of lactacystin- or MG132-treated cells. In some cells treated with higher concentrations of MG132 or lactacystin, we observed in the cortical cytoplasm (1) relatively large HSP30 staining structures, (2) colocalization of actin and HSP30, and (3) cytoplasmic areas that were devoid of HSP30. Lastly, MG132 treatment of A6 cells conferred a state of thermotolerance such that they were able to survive a subsequent thermal challenge.