Retraction Note: Fatty acids and cancer-amplified ZDHHC19 promote STAT3 activation through S-palmitoylation.

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Fatty acids and cancer-amplified ZDHHC19 promote STAT3 activation through S-palmitoylation.

Signal transducer and activator of transcription 3 (STAT3) has a critical role in regulating cell fate, inflammation and immunity1,2. Cytokines and growth factors activate STAT3 through kinase-mediated tyrosine phosphorylation and dimerization3,4. It remains unknown whether other factors promote STAT3 activation through different mechanisms. Here we show that STAT3 is post-translationally S-palmitoylated at the SRC homology 2 (SH2) domain, which promotes the dimerization and transcriptional activation of STAT3. Fatty acids can directly activate STAT3 by enhancing its palmitoylation, in synergy with cytokine stimulation. We further identified ZDHHC19 as a palmitoyl acyltransferase that regulates STAT3. Cytokine stimulation increases STAT3 palmitoylation by promoting the association between ZDHHC19 and STAT3, which is mediated by the SH3 domain of GRB2. Silencing ZDHHC19 blocks STAT3 palmitoylation and dimerization, and impairs the cytokine- and fatty-acid-induced activation of STAT3. ZDHHC19 is frequently amplified in multiple human cancers, including in 39% of lung squamous cell carcinomas. High levels of ZDHHC19 correlate with high levels of nuclear STAT3 in patient samples. In addition, knockout of ZDHHC19 in lung squamous cell carcinoma cells significantly blocks STAT3 activity, and inhibits the fatty-acid-induced formation of tumour spheres as well as tumorigenesis induced by high-fat diets in an in vivo mouse model. Our studies reveal that fatty-acid- and ZDHHC19-mediated palmitoylation are signals that regulate STAT3, which provides evidence linking the deregulation of palmitoylation to inflammation and cancer.

Auto-fatty acylation of transcription factor RFX3 regulates ciliogenesis.

Defects in cilia have been associated with an expanding human disease spectrum known as ciliopathies. Regulatory Factor X 3 (RFX3) is one of the major transcription factors required for ciliogenesis and cilia functions. In addition, RFX3 regulates pancreatic islet cell differentiation and mature ß-cell functions. However, how RFX3 protein is regulated at the posttranslational level remains poorly understood. Using chemical reporters of protein fatty acylation and mass spectrometry analysis, here we show that RFX3 transcriptional activity is regulated by S-fatty acylation at a highly conserved cysteine residue in the dimerization domain. Surprisingly, RFX3 undergoes enzyme-independent, "self-catalyzed" auto-fatty acylation and displays preferences for 18-carbon stearic acid and oleic acid. The fatty acylation-deficient mutant of RFX3 shows decreased homodimerization; fails to promote ciliary gene expression, ciliogenesis, and elongation; and impairs Hedgehog signaling. Our findings reveal a regulation of RFX3 transcription factor and link fatty acid metabolism and protein lipidation to the regulation of ciliogenesis.

ZDHHC7-mediated S-palmitoylation of Scribble regulates cell polarity.

Scribble (SCRIB) is a tumor-suppressor protein, playing critical roles in establishing and maintaining epithelial cell polarity. SCRIB is frequently amplified in human cancers but does not localize properly to cell-cell junctions, suggesting that mislocalization of SCRIB disrupts its tumor-suppressive activities. Using chemical reporters, here we showed that SCRIB localization was regulated by S-palmitoylation at conserved cysteine residues. Palmitoylation-deficient mutants of SCRIB were mislocalized, leading to disruption of cell polarity and loss of their tumor-suppressive activities to oncogenic YAP, MAPK and PI3K/AKT pathways. We further found that ZDHHC7 was the major palmitoyl acyltransferase regulating SCRIB. Knockout of ZDHHC7 led to SCRIB mislocalization and YAP activation, and disruption of SCRIB's suppressive activities in HRas(V12)-induced cell invasion. In summary, we demonstrated that ZDHHC7-mediated SCRIB palmitoylation is critical for SCRIB membrane targeting, cell polarity and tumor suppression, providing new mechanistic insights of how dynamic protein palmitoylation regulates cell polarity and tumorigenesis.

Autopalmitoylation of TEAD proteins regulates transcriptional output of the Hippo pathway.

TEA domain (TEAD) transcription factors bind to the coactivators YAP and TAZ and regulate the transcriptional output of the Hippo pathway, playing critical roles in organ size control and tumorigenesis. Protein S-palmitoylation attaches a fatty acid, palmitate, to cysteine residues and regulates protein trafficking, membrane localization and signaling activities. Using activity-based chemical probes, we discovered that human TEADs possess intrinsic palmitoylating enzyme-like activities and undergo autopalmitoylation at evolutionarily conserved cysteine residues under physiological conditions. We determined the crystal structures of lipid-bound TEADs and found that the lipid chain of palmitate inserts into a conserved deep hydrophobic pocket. Strikingly, palmitoylation did not alter TEAD's localization, but it was required for TEAD's binding to YAP and TAZ and was dispensable for its binding to the Vgll4 tumor suppressor. Moreover, palmitoylation-deficient TEAD mutants impaired TAZ-mediated muscle differentiation in vitro and tissue overgrowth mediated by the Drosophila YAP homolog Yorkie in vivo. Our study directly links autopalmitoylation to the transcriptional regulation of the Hippo pathway.

Chemical Probes to Directly Profile Palmitoleoylation of Proteins.

Palmitoleoylation is a unique fatty acylation of proteins in which a monounsaturated fatty acid, palmitoleic acid (C16:1), is covalently attached to a protein. Wnt proteins are known to be palmitoleoylated by cis-Δ9 palmitoleate at conserved serine residues. O-palmitoleoylation plays a critical role in regulating Wnt secretion, binding to the receptors, and in the dynamics of Wnt signaling. Therefore, protein palmitoleoylation is important in tissue homeostasis and tumorigenesis. Chemical probes based on saturated fatty acids, such as ω-alkynyl palmitic acid (Alk-14 or Alk-C16 ), have been used to study Wnt palmitoleoylation. However, such probes require prior conversion to the unsaturated fatty acid by stearoyl-CoA desaturase (SCD) in cells, significantly decreasing their selectivity and efficiency for studying protein palmitoleoylation. We synthesized and characterized ω-alkynyl cis- and trans-palmitoleic acids (cis- and trans-Alk-14:1) as chemical probes to directly study protein palmitoleoylation. We found that cis-Alk-14:1 could more efficiently label Wnt proteins in cells. Interestingly, the DHHC family of palmitoyl acyltransferases can charge both saturated and unsaturated fatty acids, potentially using both as acyl donors in protein palmitoylation and palmitoleoylation. Furthermore, proteomic analysis of targets labeled by these probes revealed new cis- and trans-palmitoleoylated proteins. Our studies provided new chemical tools and revealed new insights into palmitoleoylation in cell signaling.

Highly diastereo- and enantioselective palladium-catalyzed [3+2] cycloaddition of vinyl aziridines and α,ß-unsaturated ketones.

A palladium-catalyzed asymmetric [3+2] cycloaddition reaction of vinylaziridines with α,ß-unsaturated ketones, wherein the alkenes have a single activator, is realized in high diastereo- and enantioselectivity, thus affording 3,4-disubstituted pyrrolidines in high yields with excellent ee values. The introduction of a methyl group at C1 of the vinyl group the vinylaziridines greatly improves the stereochemistry of the reaction. A plausible transition state is proposed.

2-Bromopalmitate analogues as activity-based probes to explore palmitoyl acyltransferases.

Reversible S-palmitoylation is an important post-translational modification that regulates the trafficking, localization, and activity of proteins. Cysteine-rich Asp-His-His-Cys (DHHC) domain-containing enzymes are evolutionarily conserved protein palmitoyl acyltransferases (PATs). The human genome encodes 23 DHHC-PATs that regulate diverse cellular functions. Although chemical probes and proteomic methods to detect palmitoylated protein substrates have been reported, no probes for direct detection of the activity of PATs are available. Here we report the synthesis and characterization of 2-bromohexadec-15-ynoic acid and 2-bromooctadec-17-ynoic acid, which are analogues of 2-bromopalmitate (2-BP), as activity-based probes for PATs as well as other palmitoylating and 2-BP-binding enzymes. These probes will serve as new chemical tools for activity-based protein profiling to explore PATs, to dissect the functions of PATs in cell signaling and diseases, and to facilitate the identification of their inhibitors.

Synthesis and Characterization of [18F]JNJ-46356479 as the First 18F-Labeled PET Imaging Ligand for Metabotropic Glutamate Receptor 2.

PURPOSE: Metabotropic glutamate receptor 2 (mGluR2) has been implicated in various psychiatric and neurological disorders, such as schizophrenia and Alzheimer's disease. We have previously developed [11C]7 as a PET radioligand for imaging mGluR2. Herein, [18F]JNJ-46356479 ([18F]8) was synthesized and characterized as the first 18F-labeled mGluR2 imaging ligand to enhance diagnostic approaches for mGluR2-related disorders. PROCEDURES: JNJ-46356479 (8) was radiolabeled via the copper (I)-mediated radiofluorination of organoborane 9. In vivo PET imaging experiments with [18F]8 were conducted first in C57BL/6 J mice and Sprague-Dawley rats to obtain whole body biodistribution and brain uptake profile. Subsequent PET studies were done in a cynomolgus monkey (Macaca fascicularis) to investigate the uptake of [18F]8 in the brain, its metabolic stability, as well as pharmacokinetic properties. RESULTS: JNJ-46356479 (8) exhibited excellent selectivity against other mGluRs. In vivo PET imaging studies showed reversible and specific binding characteristic of [18F]8 in rodents. In the non-human primate, [18F]8 displayed good in vivo metabolic stability, excellent brain permeability, fast and reversible kinetics with moderate heterogeneity across brain regions. Pre-treatment studies with compound 7 revealed time-dependent decrease of [18F]8 accumulation in mGluR2 rich regions based on SUV values with the highest decrease in the nucleus accumbens (18.7 ± 5.9%) followed by the cerebellum (18.0 ± 7.9%), the parietal cortex (16.9 ± 7.8%), and the hippocampus (16.8 ± 6.9%), similar to results obtained in the rat studies. However, the volume of distribution (VT) results derived from 2T4k model showed enhanced VT from a blocking study with compound 7. This is probably because of the potentiating effect of compound 7 as an mGluR2 PAM as well as related non-specific binding in the tissue data. CONCLUSIONS: [18F]8 readily crosses the blood-brain barrier and demonstrates fast and reversible kinetics both in rodents and in a non-human primate. Further investigation of [18F]8 on its binding specificity would warrant translational study in human.

Durable superamphiphobic coatings with high static and dynamic repellency towards liquids with low surface tension and high viscosity.

Superamphiphobic coatings have attracted great attention in academia and industry. However, the fabrication of durable superamphiphobic coatings with high repellency towards liquids with low surface tension and high viscosity is still very challenging. Here, we report a simple method for the fabrication of durable superamphiphobic coatings with high static and dynamic repellency to such liquids. First, a homogeneous suspension was fabricated by hydrolytic condensation of silanes in the presence of the chain-like aggregates of SiO2 nanoparticles. Subsequently, the superamphiphobic coatings were fabricated by spray-coating the polyurethane adhesive onto the substrates followed by spray-coating the as-prepared suspension onto the polyurethane adhesive layer. The coatings show high repellency to liquids with low surface tension and high viscosity, e.g., high apparent contact angles, low sliding angles, high impact resistance, low horizontal deformation and fast rolling velocity. Furthermore, the coatings show excellent mechanical durability against intensive sandpaper abrasion (60 m of abrasion under 10.5 kPa), water impact (60 min under 100 kPa) and tape peeling (200 cycles). The coatings also exhibit good aging stability. Based on these merits, the superamphiphobic coatings may have great potentials in various applications, e.g., handling with natural and synthetic polymer solutions.

Design, Synthesis, and Characterization of Benzimidazole Derivatives as Positron Emission Tomography Imaging Ligands for Metabotropic Glutamate Receptor 2.

Three benzimidazole derivatives (13-15) have been synthetized as potential positron emission tomography (PET) imaging ligands for mGluR2 in the brain. Of these compounds, 13 exhibits potent binding affinity (IC50 = 7.6 ± 0.9 nM), positive allosteric modulator (PAM) activity (EC50 = 51.2 nM), and excellent selectivity against other mGluR subtypes (>100-fold). [11C]13 was synthesized via O-[11C]methylation of its phenol precursor 25 with [11C]methyl iodide. The achieved radiochemical yield was 20 ± 2% (n = 10, decay-corrected) based on [11C]CO2 with a radiochemical purity of >98% and molar activity of 98 ± 30 GBq/µmol EOS. Ex vivo biodistribution studies revealed reversible accumulation of [11C]13 and hepatobiliary and urinary excretions. PET imaging studies in rats demonstrated that [11C]13 accumulated in the mGluR2-rich brain regions. Pre-administration of mGluR2-selective PAM, 17 reduced the brain uptake of [11C]13, indicating a selective binding. Therefore, [11C]13 is a potential PET imaging ligand for mGluR2 in different central nervous system-related conditions.

3-Layer conductive metal-organic nanosheets as electrocatalysts to enable an ultralow detection limit of H2O2.

Hydrogen peroxide has been widely studied in cell biology and liquid fuel cells as an oxidant or fuel, and highly efficient and durable electrocatalysts for H2O2 reduction and detection are in high demand. Here, a simple strategy to fabricate conductive 2D single/several-layer [Co3(HHTP)2]n MOF nanosheets, based on 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and Co2+ ions, was developed by the Langmuir-Blodgett (LB) method combined with layer-by-layer (LbL) growth technology. The [Co3(HHTP)2]n MOF nanosheets successfully boosted H2O2 reduction with ultrahigh mass activity and good durability, and a new method to detect the H2O2 concentration with an ultralow detection limit of 10-7 (2.9 µmol L-1) was developed. Meanwhile, a series of factors like layer number, surface tension, pH value, ion concentration, and annealing were systematically investigated to further prove the ultrahigh accuracy, sensitivity, and durability of the as-developed H2O2 detection method. The reaction mechanism and energy transfer process of H2O2 reduction catalyzed by the metal-organic nanosheets were investigated by first principles calculations using density functional theory (DFT), showing good agreement with the experiment.

Superamphiphobic Cu/CuO Micropillar Arrays with High Repellency Towards Liquids of Extremely High Viscosity and Low Surface Tension.

For almost all the research of super anti-wetting surfaces, pure liquids like water and n-hexadecane are used as the probes. However, liquids of diverse compositions are used in academic research, industrial production and our daily life. Obviously, the liquid repellency of super anti-wetting coatings is highly dependent on properties of the liquids. Here, we report the first superamphiphobic surface with high repellency towards liquids of extremely high viscosity and low surface tension. The surfaces were prepared by constructing a hierarchical micro-/nanostructure on the Cu micropillar arrays followed by modification with perfluorosilane. The surfaces are superamphiphobic towards the liquids with extremely high viscosity and low surface tension because of (i) the micro-/nanostructured surface composed of micropillars with proper pillar distance and CuO nano-flowers, and (ii) the abundant perfluorodecyl groups on the surface. The contact angles, sliding angles, apparent contact line at the solid-liquid interface and adhesion forces are the end products of micropillar distance, viscosity and surface tension. Smaller micropillar distance, higher viscosity and higher surface tension contribute to reducing the adhesion force. We in situ observed the process of microcapillary bridge rupture for the first time using highly viscous liquids. We also successfully reduced the adhesion forces and enhanced the average rolling velocity of liquids with extremely high viscosity and low surface tension by regulating the micropillar distance.

Clay-based superamphiphobic coatings with low sliding angles for viscous liquids.

Although significant attention has been paid, most of superamphiphobic surfaces suffer from high sliding angles (SA) for liquids with low surface tension and complicated preparation methods. Also, superamphiphobic coatings with high repellency to the liquids with very high viscosity and low surface tension are rare. Here, we report preparation of clay-based superamphiphobic coatings with low SAs for viscous liquids. A homogeneous suspension was prepared by hydrolytic condensation of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and tetraethoxysilane in the existence of attapulgite, a kind of natural clay mineral with nanorods-like microstructure. The superamphiphobic coatings were readily prepared by spray-coating the suspension onto substrates. The effects of attapulgite on microstructure and superamphiphobicity of the coatings were studied. Also, the static and dynamic superamphiphobicity were investigated. The attapulgite concentration has great influences on superamphiphobicity and solid-liquid adhesion force of the coatings, as it determines microstructure of the coatings. The superamphiphobic surfaces feature high contact angles and low SAs for various liquids including those with extremely high viscosity and low surface tension, e.g., hydroxyl-terminated polybutadiene (HTPB) and the HTPB/Al mixture (1:1, w/w). The coating also shows low solid-liquid adhesion force, high impact resistance and fast rolling of various liquids.

Fewer-layer conductive metal-organic nanosheets enable ultrahigh mass activity for the oxygen evolution reaction.

A new class of 2D fewer-layer π-conjugated conductive metal-organic nanosheets was developed via the Langmuir-Blodgett method, exhibiting ultrahigh mass activity (64.63 A mg-1, 1.7 V vs. RHE) and stability for electrochemical oxygen evolution reactions (OER).

Thermal and mechanical reinforcement of a novel paraffin-based hydroxyl-terminated polybutadiene (HTPB) binder containing a three-dimension (3D) diurea-paraffin wax (DU-PW) for prevention of PW leakage.

Leakage of paraffin wax (PW) is a major concern in the development of polymer bonded explosive (PBX) systems because it relates to the amount of PW that can be used as a desensitizer or a fuel, which, in turn, affects the mechanical performance and tolerance of PBX in high-temperature environments. Hydroxyl-terminated polybutadiene (HTPB) binders significantly contribute desirable polymer features to PBX. Thus, a three-dimension (3D) high-temperature non-flowing diurea-paraffin wax (DU-PW) composite was synthesized and creatively employed to a HTPB binder. DU-PW/PW/HTPB composites with different contents of the 3D DU-PW phase change material (PCM) were prepared through a cast molding process. The differential scanning calorimetry (DSC) results demonstrate that these composites can show high phase-change enthalpies and good thermal reliability. As observed from the scanning electron microscope (SEM) photographs, adding DU-PW can clearly reduce the number of holes caused by the leaked PW on the fracture surface of DU-PW/HTPB. Moreover, the addition of DU-PW can remarkably reduce the leakage of PW and improve the thermal stability as well as mechanical properties of the PW-based HTPB. These observations present the potential of utilizing form-stable PCM (FSPCM) to solve the problem of PW leakage in PBX systems.

Preparation and properties of a novel covalently bonded energetic boron powder and its composite.

Promoting the ignition of boron powders in propellants, explosives and pyrotechnics has been a promising research direction. In this paper, a new strategy for covalently bonded energetic boron powders was designed. Specifically, 2,4-toluene diisocyanate (TDI) and 3-amino-1,2,4-triazole (ATZ) were used as grafting molecules, and then acidification, carbamation and ureylene addition were performed serially on the surface of the boron particles. The reaction conditions were optimized using infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). At lower temperatures, the addition of carbamation or ureylene can improve the yield and stability of isocyanate and urea groups. The chemical composition, microstructure and surface properties of the boron powders were analyzed with nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and contact angle (CA) analysis, respectively. The covalent bonding type was confirmed by the typical peaks at 155.7 and 157.5 ppm in the 13C NMR spectra of the intermediate isocyanate-grafting boron powders (TB) and target product triazole-grafting boron powders (TTB). The static water contact angles on the surfaces of TB and TTB were 148.3° and 37.0°, respectively. Influences of surface modification of boron powders on the rheological properties of boron/hydroxyl-terminated polybutadiene (HTPB) composites were investigated. Moreover, the prepared samples were characterized by thermogravimetry (TG) and differential scanning calorimetry (DSC) to investigate the thermal stability and reaction activity, and the results showed that this grafting strategy could significantly reduce the critical reaction temperature of B/KNO3. Consequently, it is anticipated that the modified boron powders can potentially be used in propellants, explosives and pyrotechnics with high impulses.

Highly potent visnagin derivatives inhibit Cyp1 and prevent doxorubicin cardiotoxicity.

Anthracyclines such as doxorubicin are highly effective chemotherapy agents used to treat many common malignancies. However, their use is limited by cardiotoxicity. We previously identified visnagin as protecting against doxorubicin toxicity in cardiac but not tumor cells. In this study, we sought to develop more potent visnagin analogs in order to use these analogs as tools to clarify the mechanisms of visnagin-mediated cardioprotection. Structure-activity relationship studies were performed in a zebrafish model of doxorubicin cardiomyopathy. Movement of the 5-carbonyl to the 7 position and addition of short ester side chains led to development of visnagin analogs with 1,000-fold increased potency in zebrafish and 250-fold increased potency in mice. Using proteomics, we discovered that doxorubicin caused robust induction of Cytochrome P450 family 1 (CYP1) that was mitigated by visnagin and its potent analog 23. Treatment with structurally divergent CYP1 inhibitors, as well as knockdown of CYP1A, prevented doxorubicin cardiomyopathy in zebrafish. The identification of potent cardioprotective agents may facilitate the development of new therapeutic strategies for patients receiving cardiotoxic chemotherapy. Moreover, these studies support the idea that CYP1 is an important contributor to doxorubicin cardiotoxicity and suggest that modulation of this pathway could be beneficial in the clinical setting.

Chemical Probe to Identify the Cellular Targets of the Reactive Lipid Metabolite 2- trans-Hexadecenal.

Lipid-derived electrophiles (LDEs) are reactive metabolites, which can covalently modify proteins and DNA and regulate diverse cellular processes. 2- trans-Hexadecenal (2-HD) is a byproduct of sphingolipid metabolism, involved in cytoskeletal reorganization, DNA damage, and apoptosis. In addition, the loss of ALDH3A2, an enzyme removing 2-HD in cells, is responsible for Sjörgen-Larsson Syndrome (SJS), suggesting that accumulation of 2-HD could lead to pathogenesis. However, the targets and the precise mechanisms of 2-HD are not well characterized. Herein, we report an alkyne-2-HD derivative as a bioorthogonal probe to explore the functions of 2-HD. We identified more than 500 potential cellular targets. Among them, the pro-apoptotic protein Bax can be covalently modified by 2-HD directly at the conserved Cys62 residue. Our work provided new chemical tools to explore the cellular functions of LDEs and revealed new mechanistic insights of the deregulation of lipid metabolism in diseases.

A high-conductance chemo-optogenetic system based on the vertebrate channel Trpa1b.

Optogenetics is a powerful research approach that allows localized optical modulation of selected cells within an animal via the expression of genetically encoded photo-excitable ion channels. Commonly used optogenetic techniques rely on the expression of microbial opsin variants, which have many excellent features but suffer from various degrees of blue spectral overlap and limited channel conductance. Here, we expand the optogenetics toolbox in the form of a tunable, high-conductance vertebrate cation channel, zTrpa1b, coupled with photo-activated channel ligands, such as optovin and 4g6. Our results demonstrate that zTrpa1b/ligand pairing offers high light sensitivity, millisecond-scale response latency in vivo, as well as adjustable channel off latency. Exogenous in vivo expression of zTrpa1b in sensory neurons allowed subcellular photo-activation, enabling light-dependent motor control. zTrpa1b/ligand was also suitable for cardiomyocyte pacing, as shown in experiments performed on zebrafish hearts in vivo as well as in human stem cell-derived cardiomyocytes in vitro. Therefore, zTrpa1b/optovin represents a novel tool for flexible, high-conductance optogenetics.