PRMT5 inhibition attenuates cartilage degradation by reducing MAPK and NF-κB signaling

Objectives

A role for the type II arginine methyltransferase PRMT5 in various human diseases has been identified. In this study, the potential mechanism underlying the involvement of PRMT5 in the pathological process leading to osteoarthritis (OA) was investigated.

Methods

PRMT5 expression in cartilage tissues from patients with OA and control individuals was assessed by immunohistochemical staining. The regulatory and functional roles of PRMT5 in the chondrocytes of patients with OA and control individuals were determined by western blotting and reverse transcription polymerase chain reaction. The effects of the PRMT5 inhibitor EPZ on interleukin-1β-induced inflammation were examined in the chondrocytes of patients with OA and in the destabilized medial meniscus (DMM) of a mouse model of OA.

Results

PRMT5 was specifically upregulated in the cartilage of patients with OA. Moreover, adenovirus-mediated overexpression of PRMT5 in human chondrocytes caused cartilage degeneration. This degeneration was induced by elevated expression levels of matrix-degrading enzymes (matrix metalloproteinase-3 (MMP-3) and matrix metalloproteinase-13 (MMP-13)) in chondrocytes. The activation of the MAPK and nuclear factor κB signaling pathways was evidenced by elevated levels of p-p65, p-p38, and p-JNK. These effects were attenuated by inhibiting the expression of PRMT5. In the mouse model, EPZ inhibited PRMT5 expression, thus protecting mouse cartilage from DMM-induced OA.

Conclusions

Our results demonstrate that PRMT5 is a crucial regulator of OA pathogenesis, implying that EPZ has therapeutic value in the treatment of this cartilage-destroying disease.

Integrated transcriptome and phosphoproteome analyses reveal that fads2 is critical for maintaining body LC-PUFA homeostasis

Fatty acid desaturate 2 (Fads2) is associated with many chronic diseases. Nevertheless, comprehensive researches on its role have not been performed. We here conducted an integrated analysis of long-chain polyunsaturated fatty acid (LC-PUFA) metabolism of fads2-deletion zebrafish (fads2^-/-) by transcriptomics, proteomics and phosphoproteomics. Compared with wild type zebrafish (WT), fads2^-/- showed significantly higher contents of hepatic linoleic acid (all-cis-9,12-C18:2), α-linolenic acid (all-cis-9,12,15-C18:3) and docosapetaenoic acid (all-cis-7,10,13,16,19-C22:5), and lower contents of γ-linolenic acid (all-cis-6,9,12-C18:3), stearidonic acid (all-cis-6,9,12,15-C18:4) and docosahexaenoic acid (all-cis-4,7,10,13,16,19-C22:6), accompanied by an increased n-6/n-3 PUFA level. In total, we identified 1608 differentially expressed genes (DEGs), 209 differentially expressed proteins (DEPs) and 153 differentially expressed phosphorylated proteins (DEPPs) with 190 sites between fads2^-/- and WT. Transcriptome and proteome analysis simultaneously aggregated these DEGs and DEPs into LC-PUFA synthesis and PPAR signaling pathways. Further interaction network analysis of the DEPPs showed that spliceosome and protein processing in endoplasmic reticulum pathway were critical groups. Additionally, we determined seven highly phosphorylated kinases and a highly expressed phosphatase in fads2^-/- zebrafish. These results give insights into the mechanism by which fads2 affects metabolic disease occurrence, and provide datasets for target selections for human disease treatment. SIGNIFICANCE: Balanced LC-PUFA composition was deeply associated with body health, while changes of LC-PUFAs usually induced serious diseases such as cardiovascular disease, type 2 diabetes and inflammatory disease. Fatty acid desaturase 2 (Fads2), subordinating to the fatty acid desaturase protein family, catalyzes the first desaturation reaction in LC-PUFA synthesis. Although Fads2 is associated with many chronic diseases including metabolic abnormalities, type 2 diabetes and obesity, comprehensive researches on its role have not been performed. On the basis of the integrated transcriptome, proteome and phosphoproteome analysis, we identified that fads2 was critical for maintaining body LC-PUFA homeostasis. Moreover, the crucial pathways including PPAR signaling pathway, spliceosome and protein processing in endoplasmic reticulum pathway, and candidate kinase targets associated with LC-PUFA metabolism were determined. These findings will contribute to the revealing of the mechanism and supply possible datasets for target selection for human disease treatment.

Modulation of phosphatidylinositol 3-kinase activity during in vitro oocyte maturation increases the production of bovine blastocysts

This study aimed to evaluate the effect of regulating phosphatidylinositol 3-kinase (PI3K) activity on the kinetics of oocyte nuclear maturation and the blastocyst rate. To evaluate oocyte viability, nuclear maturation rate and in vitro embryo production, cumulus-oocyte complexes (COCs) were maintained for 0, 10 min, 6 h or 22 h in TCM 199 medium supplemented with 20 nM wortmannin, an inhibitor of PI3K. After each period, COCs were transferred to the same medium without wortmannin and kept under the same conditions until completion of 22 h of in vitro maturation (IVM). To evaluate the effect of time on progression of nuclear maturation, COCs cultivated with 20 nM wortmannin was maintained for 22, 28 or 34 h of IVM. To determine the effect of wortmannin on the activity of maturation-promoting factor (MPF), COCs were kept under IVM conditions in the presence of the inhibitor for 0, 1, 3, 6, or 8 h. Exposure of COCs to wortmannin decreased (P < 0.05) the percentage of oocytes that reached metaphase II (MII) up to 22 h, MPF activity and reduced PI3K activity by 30%. However, after 28 and 34 h, 70% of oocytes reached the MII stage in the presence of inhibitor Moreover, COCs matured in the presence of wortmannin showed an increase (P < 0.05) in the blastocyst rate. These findings suggested that the regulation of the PI3K activity during IVM of bovine COCs interfered with the meiotic progression due to control of MPF activity, positively affecting the blastocyst rate.

Potential therapeutic approaches for a sleeping pathogen: tuberculosis a case for bioinorganic chemistry

Mycobacterium tuberculosis (Mtb) has an old history as a human pathogen and still kills over one million people every year. One key feature of this bacterium is its dormancy: a phenomenon responsible for major changes in its metabolism and replication that have been associated with the need for a lengthy therapy for Mtb. This process is regulated by key heme-based sensors, particularly DosT and DevS (DosS), among other co-regulators, and also linked to nitrogen utilization (nitrate/nitrite) and stringent responses. In face of the current threat of tuberculosis, there is an urgent need to develop new therapeutic agents capable of targeting the dormant state, associated with the need for a lengthy therapy. Interestingly, many of those key proteins are indeed metallo-containing or metallo-dependent biomolecules, opening exciting bioinorganic opportunities. Here, we critically reviewed a series of small molecules targeting key proteins involved in these processes, including DosT/DevS/DevR, RegX3, MprA, MtrA, NarL, PknB, Rel, PPK, nitrate and nitrite reductases, GlnA1, aiming for new opportunities and alternative therapies. In the battle against Mycobacterium tuberculosis, new drug targets must be searched, in particular  those involved in dormancy. A series of exciting cases for drug development involving metallo-containing or metallo-dependent biomolecules are reviewed, opening great opportunities for the bioinorganic chemistry community.

Exploring the beneficial role of telmisartan in sepsis-induced myocardial injury through inhibition of high-mobility group box 1 and glycogen synthase kinase-3β/nuclear factor-κB pathway

In the present experimental study, cecal ligation and puncture significantly increased the myocardial injury assessed in terms of excess release of creative kinase-MB (CK-MB), cardiac troponin I (cTnI), interleukin (IL)-6 and decrease of IL-10 in the blood following 12 h of laparotomy procedure as compared to normal control. Also, a significant increase in protein expression levels of high-mobility group box 1 (HMGB1) and decreased phosphorylation of glycogen synthase kinase-3β (GSK-3β) was observed in the myocardial tissue as compared to normal control. A single independent administration of telmisartan (2 and 4 mg/kg) and AR-A014418 (1 and 2 mg/kg) substantially reduced sepsis-induced myocardial injury in terms of decrease levels of CK-MB, cTnI and IL-6, HMGB1, GSK-3β and increase in IL-10 and p-GSK-3β in the blood in sepsis- subjected rats. The effects of telmisartan at dose 4 mg/kg and AR-A014418 at a dose of 2 mg/kg were significantly higher than the telmisartan at a dose of 2 mg/kg and AR-A014418 1 mg/kg respectively. Further, no significant effects on different parameters were observed in the sham control group in comparison to normal. Therefore it is plausible to suggest that sepsis may increase the levels of angiotensin II to trigger GSK-3β-dependent signaling to activate the HMGB1/receptors for advanced glycation end products, which may promote inflammation and myocardial injury in sepsis-subjected rats.

Non-'classical' MEKs: A review of MEK3-7 inhibitors

The MAPK pathways are an enduring area of interest due to their essential roles in cell processes. Increased expression and activity can lead to a multitude of diseases, sparking research efforts in developing inhibitors against these kinases. Though great strides have been made in developing MEK1/2 inhibitors, there is a notable lack of chemical probes for MEK3-7, given their central role in stimuli response, cell growth, and development. This review summarizes the progress that has been made on developing small molecule probes for MEK3-7, the specific disease states in which they have been studied, and their potential to become novel therapeutics.

Understanding the early cold response mechanism in IR64 indica rice variety through comparative transcriptome analysis

Background

Cellular reprogramming in response to environmental stress involves alteration of gene expression, changes in the protein and metabolite profile for ensuring better stress management in plants. Similar to other plant species originating in tropical and sub-tropical areas, indica rice is highly sensitive to low temperature that adversely affects its growth and grain productivity. Substantial work has been done to understand cold induced changes in gene expression in rice plants. However, adequate information is not available for early gene expression, especially in indica variety. Therefore, a transcriptome profile was generated for cold shock treated seedlings of IR64 variety to identify early responsive genes.

Results

The functional annotation of early DEGs shows enrichment of genes involved in altered membrane rigidity and electrolytic leakage, the onset of calcium signaling, ROS generation and activation of stress responsive transcription factors in IR64. Gene regulatory network suggests that cold shock induced Ca2+ signaling activates DREB/CBF pathway and other groups of transcription factors such as MYB, NAC and ZFP; for activating various cold-responsive genes. The analysis also indicates that cold induced signaling proteins like RLKs, RLCKs, CDPKs and MAPKK and ROS signaling proteins. Further, several late-embryogenesis-abundant (LEA), dehydrins and low temperature-induced-genes were upregulated under early cold shock condition, indicating the onset of water-deficit conditions. Expression profiling in different high yielding cultivars shows high expression of cold-responsive genes in Heera and CB1 indica varieties. These varieties show low levels of cold induced ROS production, electrolytic leakage and high germination rate post-cold stress, compared to IR36 and IR64. Collectively, these results suggest that these varieties may have improved adaptability to cold stress.

Conclusions

The results of this study provide insights about early responsive events in Oryza sativa l.ssp. indica cv IR64 in response to cold stress. Our data shows the onset of cold response is associated with upregulation of stress responsive TFs, hydrophilic proteins and signaling molecules, whereas, the genes coding for cellular biosynthetic enzymes, cell cycle control and growth-related TFs are downregulated. This study reports that the generation of ROS is integral to the early response to trigger the ROS mediated signaling events during later stages.

Phosphoproteomics of short-term hedgehog signaling in human medulloblastoma cells

BACKGROUND

Aberrant hedgehog (HH) signaling is implicated in the development of various cancer entities such as medulloblastoma. Activation of GLI transcription factors was revealed as the driving force upon pathway activation. Increased phosphorylation of essential effectors such as Smoothened (SMO) and GLI proteins by kinases including Protein Kinase A, Casein Kinase 1, and Glycogen Synthase Kinase 3 β controls effector activity, stability and processing. However, a deeper and more comprehensive understanding of phosphorylation in the signal transduction remains unclear, particularly during early response processes involved in SMO activation and preceding GLI target gene regulation.

METHODS

We applied temporal quantitative phosphoproteomics to reveal phosphorylation dynamics underlying the short-term chemical activation and inhibition of early hedgehog signaling in HH responsive human medulloblastoma cells. Medulloblastoma cells were treated for 5.0 and 15 min with Smoothened Agonist (SAG) to induce and with vismodegib to inhibit the HH pathway.

RESULTS

Our phosphoproteomic profiling resulted in the quantification of 7700 and 10,000 phosphosites after 5.0 and 15 min treatment, respectively. The data suggest a central role of phosphorylation in the regulation of ciliary assembly, trafficking, and signal transduction already after 5.0 min treatment. ERK/MAPK signaling, besides Protein Kinase A signaling and mTOR signaling, were differentially regulated after short-term treatment. Activation of Polo-like Kinase 1 and inhibition of Casein Kinase 2A1 were characteristic for vismodegib treatment, while SAG treatment induced Aurora Kinase A activity. Distinctive phosphorylation of central players of HH signaling such as SMO, SUFU, GLI2 and GLI3 was observed only after 15 min treatment.

CONCLUSIONS

This study provides evidence that phosphorylation triggered in response to SMO modulation dictates the localization of hedgehog pathway components within the primary cilium and affects the regulation of the SMO-SUFU-GLI axis. The data are relevant for the development of targeted therapies of HH-associated cancers including sonic HH-type medulloblastoma. A deeper understanding of the mechanisms of action of SMO inhibitors such as vismodegib may lead to the development of compounds causing fewer adverse effects and lower frequencies of drug resistance. Video Abstract.

Signaling pathways targeting mitochondrial potassium channels

In this review, we describe key signaling pathways regulating potassium channels present in the inner mitochondrial membrane. The signaling cascades covered here include phosphorylation, redox reactions, modulation by calcium ions and nucleotides. The following types of potassium channels have been identified in the inner mitochondrial membrane of various tissues: ATP-sensitive, Ca²⁺-activated, voltage-gated and two-pore domain potassium channels. The direct roles of these channels involve regulation of mitochondrial respiration, membrane potential and synthesis of reactive oxygen species (ROS). Changes in channel activity lead to diverse pro-life and pro-death responses in different cell types. Hence, characterizing the signaling pathways regulating mitochondrial potassium channels will facilitate understanding the physiological role of these proteins. Additionally, we describe in this paper certain regulatory mechanisms, which are unique to mitochondrial potassium channels.

Selected arylsulphonyl pyrazole derivatives as potential Chk1 kinase ligands-computational investigations

Protein kinases control diversity of biochemical processes in human organism. Checkpoint 1 kinase (Chk1) is an important element of the checkpoint signalling pathways and is responsible for DNA damage repair. Hence, this kinase plays an essential role in cancer cells survival and has become an important target for anticancer agents. Our previous investigations showed that some arylsulphonyl indazole derivatives displayed anticancer effect in vitro. In the present study, in order to verify possibility of interactions of pyrazole and indazole derivatives with Chk1, we focused on the docking of selected tosyl derivatives of indazole and condensed pyrazole 1-7 to the Chk1 pocket, analysis of interactions involving optimized ligand-protein system using DFT formalism, and estimation of the interaction enthalpy of the ligand-protein complex by applying the PM7 method. The estimation of binding affinity seems to indicate that the indazole 5-substituted with 3,5-dimethylpyrazole 4 and condensed pyrazoloquinoline derivative 7 fit the best to the Chk1-binding pocket. The values of the energy of interaction, i.e. the enthalpy change (ΔHint), were between - 85.06 and - 124.04 kcal mol-1 for the optimized ligand-Chk1 complexes. The relaxation of the ligands within the complexes azole-protein as well as the distribution of hydrogen contacts between the ligands and kinase pocket amino acids was also analysed using molecular dynamics as a supporting method. Graphical Abstract Presentation of methods used to describe the interactions between arylsulphonyl pyrazole derivatives and Chk1 kinase.

Identification of a new series of flavopiridol-like structures as kinase inhibitors with high cytotoxic potency

In this work, unique flavopiridol analogs bearing thiosugars, amino acids and heterocyclic moieties tethered to the flavopiridol via thioether and amine bonds mainly on its C ring have been prepared. The analogs bearing thioether-benzimidazoles as substituents have demonstrated high cytotoxic activity in vitro against up to seven cancer cell lines. Their cytotoxic effects are comparable to those of flavopiridol. The most active compound 13c resulting from a structure-activity relationship (SAR) study and in silico docking showed the best antiproliferative activity and was more efficient than the reference compound. In addition, compound 13c showed significant nanomolar inhibition against CDK9, CDK10, and GSK3β protein kinases.

AMPK Interactome Reveals New Function in Non-homologous End Joining DNA Repair

Adenosine monophosphate-activated protein kinase (AMPK) is an obligate heterotrimer that consists of a catalytic subunit (α) and two regulatory subunits (β and γ). AMPK is a key enzyme in the regulation of cellular energy homeostasis. It has been well studied and is known to function in many cellular pathways. However, the interactome of AMPK has not yet been systematically established, although protein-protein interaction is critically important for protein function and regulation. Here, we used tandem-affinity purification, coupled with mass spectrometry (TAP-MS) analysis, to determine the interactome of AMPK and its functions. We conducted a TAP-MS analysis of all seven AMPK subunits. We identified 138 candidate high-confidence interacting proteins (HCIPs) of AMPK, which allowed us to build an interaction network of AMPK complexes. Five candidate AMPK-binding proteins were experimentally validated, underlining the reliability of our data set. Furthermore, we demonstrated that AMPK acts with a strong AMPK-binding protein, Artemis, in non-homologous end joining. Collectively, our study established the first AMPK interactome and uncovered a new function of AMPK in DNA repair.

Development of 2-(4-pyridyl)-benzimidazoles as PKN2 chemical tools to probe cancer

Kinases are signalling proteins which have proven to be successful targets for the treatment of a variety of diseases, predominantly in cancers. However, only a small proportion of kinases (<20%) have been investigated for their therapeutic viability, likely due to the lack of available chemical tools across the kinome. In this work we describe initial efforts in the development of a selective chemical tool for protein kinase N2 (PKN2), a relatively unexplored kinase of interest in several types of cancer. The most successful compound, 5, has a measured IC₅₀ of 0.064 μM against PKN2, with ca. 17-fold selectivity over close homologue, PKN1.

Alpha technology: A powerful tool to detect mouse brain intracellular signaling events

BACKGROUND

Phosphorylation by protein kinases is a fundamental molecular process involved in the regulation of signaling activities in living organisms. Understanding this complex network of phosphorylation, especially phosphoproteins, is a necessary step for grasping the basis of cellular pathophysiology. Studying brain intracellular signaling is a particularly complex task due to the heterogeneous complex nature of the brain tissue, which consists of many embedded structures.

NEW METHOD

Overcoming this degree of complexity requires a technology with a high throughput and economical in the amount of biological material used, so that a large number of signaling pathways may be analyzed in a large number of samples. We have turned to Alpha (Amplified Luminescent Proximity Homogeneous Assay) technology.

COMPARISON WITH EXISTING METHOD

Western blot is certainly the most commonly used method to measure the phosphorylation state of proteins. Even though Western blot is an accurate and reliable method for analyzing modifications of proteins, it is a time-consuming and large amounts of samples are required. Those two parameters are critical when the goal of the research is to comprehend multi-signaling proteic events so as to analyze several targets from small brain areas.

RESULT

Here we demonstrate that Alpha technology is particularly suitable for studying brain signaling pathways by allowing rapid, sensitive, reproducible and semi-quantitative detection of phosphoproteins from individual mouse brain tissue homogenates and from cell fractionation and synaptosomal preparations of mouse hippocampus.

CONCLUSION

Alpha technology represents a major experimental step forward in unraveling the brain phosphoprotein-related molecular mechanisms involved in brain-related disorders.

Molecular Basis of the Mechanisms Controlling MASTL

The human MASTL (Microtubule-associated serine/threonine kinase-like) gene encodes an essential protein in the cell cycle. MASTL is a key factor preventing early dephosphorylation of M-phase targets of Cdk1/CycB. Little is known about the mechanism of MASTL activation and regulation. MASTL contains a non-conserved insertion of 550 residues within its activation loop, splitting the kinase domain, and making it unique. Here, we show that this non-conserved middle region (NCMR) of the protein is crucial for target specificity and activity. We performed a phosphoproteomic assay with different MASTL constructs identifying key phosphorylation sites for its activation and determining whether they arise from autophosphorylation or exogenous kinases, thus generating an activation model. Hydrogen/deuterium exchange data complements this analysis revealing that the C-lobe in full-length MASTL forms a stable structure, whereas the N-lobe is dynamic and the NCMR and C-tail contain few localized regions with higher-order structure. Our results indicate that truncated versions of MASTL conserving a cryptic C-Lobe in the NCMR, display catalytic activity and different targets, thus establishing a possible link with truncated mutations observed in cancer-related databases.

Calcium Dynamics and Synaptic Plasticity

Synaptic plasticity is a fundamental property of neurons referring to the activity-dependent changes in the strength and efficacy of synaptic transmission at preexisting synapses. Such changes can last from milliseconds to hours, days, or even longer and are involved in learning and memory as well as in development and response of the brain to injuries. Several types of synaptic plasticity have been described across neuronal types, brain regions, and species, but all of them share in one way or another capital importance of Ca²⁺-mediated processes. In this chapter, we will focus on the Ca²⁺-dependent events necessary for the induction and expression of multiple forms of synaptic plasticity.

Multiple Site-Specific Phosphorylation of IDPs Monitored by NMR

In line with their high accessibility, disordered proteins are exquisite targets of kinases. Eukaryotic organisms use the so-called intrinsically disordered proteins (IDPs) or intrinsically disordered regions of proteins (IDRs) as molecular switches carrying intracellular information tuned by reversible phosphorylation schemes. Solvent-exposed serines and threonines are abundant in IDPs, and, consistently, kinases often modify disordered regions of proteins at multiple sites. In this context, nuclear magnetic resonance (NMR) spectroscopy provides quantitative, residue-specific information that permits mapping of phosphosites and monitoring of their individual kinetics. Hence, NMR monitoring emerges as an in vitro approach, complementary to mass-spectrometry or immuno-blotting, to characterize IDP phosphorylation comprehensively. Here, we describe in detail generic protocols for carrying out NMR monitoring of IDP phosphorylation, and we provide a number of practical insights that improve handiness and reproducibility of this method.

A Short Historical Perspective of Methods in Inositol Phosphate Research

The multitudinous inositol phosphate family elicits a wide range of molecular effects that regulate countless biological responses. In this review, I provide a methodological viewpoint of the manner in which key advances in the field of inositol phosphate research were made. I also note some of the considerable challenges that still lie ahead.

Pharmacological inhibition of TAK1, with the selective inhibitor takinib, alleviates clinical manifestation of arthritis in CIA mice

OBJECTIVES

To examine the ability of takinib, a selective transforming growth factor beta-activated kinase 1 (TAK1) inhibitor, to reduce the severity of murine type II collagen-induced arthritis (CIA), and to affect function of synovial cells.

METHODS

Following the induction of CIA, mice were treated daily with takinib (50 mg/kg) and clinical scores assessed. Thirty-six days post-CIA induction, histology was performed on various joints of treated and vehicle-treated animals. Inflammation, pannus, cartilage damage, bone resorption, and periosteal bone formation were quantified. Furthermore, pharmacokinetics of takinib were evaluated by LC-MS in various tissues. Rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) cells were cultured with 10 μM takinib and cytokine secretion analyzed by cytokine/chemokine proteome array. Cytotoxicity of takinib for RA-FLS was measured with 24 to 48 h cultures in the presence or absence of tumor necrosis factor (TNF).

RESULTS

Here, we show takinib's ability to reduce the clinical score in the CIA mouse model of rheumatoid arthritis (RA) (p < 0.001). TAK1 inhibition reduced inflammation (p < 0.01), cartilage damage (p < 0.01), pannus, bone resorption, and periosteal bone formation and periosteal bone width in all joints of treated mice compared to vehicle treated. Significant reduction of inflammation (p < 0.004) and cartilage damage (p < 0.004) were observed in the knees of diseased treated animals, with moderate reduction seen in the forepaws and hind paws. Furthermore, the pharmacokinetics of takinib show rapid plasma clearance (t_½ = 21 min). In stimulated RA-FLS cells, takinib reduced GROα, G-CSF, and ICAM-1 pro-inflammatory cytokine signaling.

CONCLUSION

Our findings support the hypothesis that TAK1 targeted therapy represents a novel therapeutic axis to treat RA and other inflammatory diseases.

Imaging dynamic cell signaling in vivo with new classes of fluorescent reporters

Dynamical features of cell signaling are the essence of living organisms. To understand animal development, it is fundamental to investigate signaling dynamics in vivo. Robust reporters are required to visualize spatial and temporal dynamics of enzyme activities and protein-protein interactions involved in signaling pathways. In this review, we summarize recent development in the design of new classes of fluorescent reporters for imaging dynamic activities of proteases, kinases, and protein-protein interactions. These reporters operate on new physical and/or chemical principles; achieve large dynamic range, high brightness, and fast kinetics; and reveal spatiotemporal dynamics of signaling that is correlated with developmental events such as embryonic morphogenesis in live animals including Drosophila and zebrafish. Therefore, many of these reporters are great tools for biological discovery and mechanistic understanding of animal development and disease progression.

Elevated Hexokinase II Expression Confers Acquired Resistance to 4-Hydroxytamoxifen in Breast Cancer Cells

Tamoxifen has been clinically used in treating estrogen receptor (ER)-positive breast cancer for over 30 years. The most challenging aspect associated with tamoxifen therapy is the development of resistance in initially responsive breast tumors. We applied a parallel-reaction monitoring (PRM)-based quantitative proteomic method to examine the differential expression of kinase proteins in MCF-7 and the isogenic tamoxifen-resistant (TamR) cells. We were able to quantify the relative protein expression levels of 315 kinases, among which hexokinase 2 (HK2) and mTOR were up-regulated in TamR MCF-7 cells. We also observed that the TamR MCF-7 cells exhibited elevated rate of glycolysis than the parental MCF-7 cells. In addition, we found that phosphorylation of S6K - a target of mTOR - was much lower in TamR MCF-7 cells, and this phosphorylation level could be restored upon genetic depletion or pharmacological inhibition of HK2. Reciprocally, the level of S6K phosphorylation was diminished upon overexpression of HK2 in MCF-7 cells. Moreover, we observed that HK2 interacts with mTOR, and this interaction inhibits mTOR activity. Lower mTOR activity led to augmented autophagy, which conferred resistance of MCF-7 cells toward tamoxifen. Together, our study demonstrates that elevated expression of HK2 promotes autophagy through inhibiting the mTOR-S6K signaling pathway and results in resistance of MCF-7 breast cancer cells toward tamoxifen; thus, our results uncovered, for the first time, HK2 as a potential therapeutic target for overcoming tamoxifen resistance.

The activity of Aurora kinase B is required for dengue virus release

Flaviviruses, such as Dengue (DENV), Zika, Yellow Fever, Japanese Encephalitis and West Nile are important pathogens with high morbidity and mortality. The last estimation indicates that ∼390 millions of people are infected by DENV per year. The DENV replicative cycle occurs mainly in the cytoplasm of the infected cells and different cytoplasmic, nuclear and mitochondrial proteins participate in viral replication. In this paper we analyzed the participation of Aurora kinase B (AurKB) in the DENV replicative cycle using the specific AurKB inhibitor ZM 447439. The kinase inhibition does not alter the viral protein production/secretion or genome replication but impaired the viral yield without altering the percentage of infected cells. Moreover, confocal microscopy analysis of DENV-infected ZM 447439-treated cells show a delocalization of viral components from the replicative complexes. In summary, these observations indicate that AurKB participates in DENV viral morphogenesis or release.

EphB2 receptor cell-autonomous forward signaling mediates auditory memory recall and learning-driven spinogenesis

While ephrin-B ligands and EphB receptors are expressed to high levels in the learning centers of the brain, it remains largely unknown how their trans-synaptic interactions contribute to memory. We find that EphB2 forward signaling is needed for contextual and sound-evoked memory recall and that constitutive over-activation of the receptor's intracellular tyrosine kinase domain results in enhanced memory. Loss of EphB2 expression does not affect the number of neurons activated following encoding, although a reduction of neurons activated after the sound-cued retrieval test was detected in the auditory cortex and hippocampal CA1. Further, spine density and maturation was reduced in the auditory cortex of mutants especially in the neurons that were dual-activated during both encoding and retrieval. Our data demonstrates that trans-synaptic ephrin-B-EphB2 interactions and forward signaling facilitate neural activation and structural plasticity in learning-associated neurons involved in the generation of memories.

Phosphatidylinositol 3 monophosphate metabolizing enzymes in blood platelet production and in thrombosis

Blood platelets, produced by the fragmentation of megakaryocytes, play a key role in hemostasis and thrombosis. Being implicated in atherothrombosis and other thromboembolic disorders, they represent a major therapeutic target for antithrombotic drug development. Several recent studies have highlighted an important role for the lipid phosphatidylinositol 3 monophosphate (PtdIns3P) in megakaryocytes and platelets. PtdIns3P, present in small amounts in mammalian cells, is involved in the control of endocytic trafficking and autophagy. Its metabolism is finely regulated by specific kinases and phosphatases. Class II (α, β and γ) and III (Vps34) phosphoinositide-3-kinases (PI3Ks), INPP4 and Fig4 are involved in the production of PtdIns3P whereas PIKFyve, myotubularins (MTMs) and type II PIPK metabolize PtdIns3P. By regulating the turnover of different pools of PtdIns3P, class II (PI3KC2α) and class III (Vps34) PI3Ks have been recently involved in the regulation of platelet production and functions. These pools of PtdIns3P appear to modulate membrane organization and intracellular trafficking. Moreover, PIKFyve and INPP4 have been recently implicated in arterial thrombosis. In this review, we will discuss the role of PtdIns3P metabolizing enzymes in platelet production and function. Potential new anti-thrombotic therapeutic perspectives based on inhibitors targeting specifically PtdIns3P metabolizing enzymes will also be commented.

Systems-level Analysis Reveals Multiple Modulators of Epithelial-mesenchymal Transition and Identifies DNAJB4 and CD81 as Novel Metastasis Inducers in Breast Cancer

Epithelial-mesenchymal transition (EMT) is driven by complex signaling events that induce dramatic biochemical and morphological changes whereby epithelial cells are converted into cancer cells. However, the underlying molecular mechanisms remain elusive. Here, we used mass spectrometry based quantitative proteomics approach to systematically analyze the post-translational biochemical changes that drive differentiation of human mammary epithelial (HMLE) cells into mesenchymal. We identified 314 proteins out of more than 6,000 unique proteins and 871 phosphopeptides out of more than 7,000 unique phosphopeptides as differentially regulated. We found that phosphoproteome is more unstable and prone to changes during EMT compared with the proteome and multiple alterations at proteome level are not thoroughly represented by transcriptional data highlighting the necessity of proteome level analysis. We discovered cell state specific signaling pathways, such as Hippo, sphingolipid signaling, and unfolded protein response (UPR) by modeling the networks of regulated proteins and potential kinase-substrate groups. We identified two novel factors for EMT whose expression increased on EMT induction: DnaJ heat shock protein family (Hsp40) member B4 (DNAJB4) and cluster of differentiation 81 (CD81). Suppression of DNAJB4 or CD81 in mesenchymal breast cancer cells resulted in decreased cell migration in vitro and led to reduced primary tumor growth, extravasation, and lung metastasis in vivo Overall, we performed the global proteomic and phosphoproteomic analyses of EMT, identified and validated new mRNA and/or protein level modulators of EMT. This work also provides a unique platform and resource for future studies focusing on metastasis and drug resistance.