TSC2 loss in neural progenitor cells suppresses translation of ASD/NDD-associated transcripts in an mTORC1- and MNK1/2-reversible fashion

Tuberous sclerosis complex (TSC), an inherited neurodevelopmental (ND) disorder with frequent manifestations of epilepsy and autism spectrum disorder (ASD). TSC is caused by mutations in TSC1 or TSC2 tumor suppressor genes, with encoded proteins hamartin/TSC1 and tuberin/TSC2 forming a functional complex inhibiting mechanistic target of rapamycin complex-1 (mTORC1) signaling, leading to FDA-approved allosteric mTORC1-selective rapamycin analogs for TSC tumors. Rapalogs are effective for TSC-associated hamartomas, however, they are not effective for treating ND manifestations. mTORC1 signaling plays an essential role in protein synthesis through mTORC1-eIF4F and MNK-eIF4E-mediated mRNA translation. Further, the effects on mRNA translation by specific mTORC1 and MNK inhibitors such as RMC-6272 and eFT-508 in TSC have never been explored. Here, employing CRISPR-modified, isogenic TSC2 patient-derived neural progenitor cells (NPCs), we have examined mRNA translation upon loss of TSC2 . Our results reveal dysregulated translation in TSC2 -Null NPCs, which significantly overlap with the translatome from TSC1 -Null NPCs, which we reported recently. Most notably, numerous non-monogenic ASD-NDD- and epilepsy-associated genes identified in patients harboring putative loss-of-function mutations, including protein truncating, or damaging missense variants, were translationally suppressed in TSC2 -Null NPCs, and their translation were reversed upon RMC-6272 or eFT-508 treatment. Our study here establishes the importance of mTORC1-eIF4F and MNK-eIF4E-mediated mRNA translation in TSC, ASD and other neurodevelopmental disorders and lay the groundwork for evaluating drugs in clinical development that target these pathways as a treatment strategy for TSC as well as ASD/NDD.

MNK, mTOR or eIF4E-selecting the best anti-tumor target for blocking translation initiation

Overexpression of eIF4E is common in patients with various solid tumors and hematologic cancers. As a potential anti-cancer target, eIF4E has attracted extensive attention from researchers. At the same time, mTOR kinases inhibitors and MNK kinases inhibitors, which are directly related to regulation of eIF4E, have been rapidly developed. To explore the optimal anti-cancer targets among MNK, mTOR, and eIF4E, this review provides a detailed classification and description of the anti-cancer activities of promising compounds. In addition, the structures and activities of some dual-target inhibitors are briefly described. By analyzing the different characteristics of the inhibitors, it can be concluded that MNK1/2 and eIF4E/eIF4G interaction inhibitors are superior to mTOR inhibitors. Simultaneous inhibition of MNK and eIF4E/eIF4G interaction may be the most promising anti-cancer method for targeting translation initiation.

eIF4E phosphorylation recruits β-catenin to mRNA cap and promotes Wnt pathway translation in dentate gyrus LTP maintenance

The mRNA cap-binding protein, eukaryotic initiation factor 4E (eIF4E), is crucial for translation and regulated by Ser209 phosphorylation. However, the biochemical and physiological role of eIF4E phosphorylation in translational control of long-term synaptic plasticity is unknown. We demonstrate that phospho-ablated Eif4e^S209A Knockin mice are profoundly impaired in dentate gyrus LTP maintenance in vivo, whereas basal perforant path-evoked transmission and LTP induction are intact. mRNA cap-pulldown assays show that phosphorylation is required for synaptic activity-induced removal of translational repressors from eIF4E, allowing initiation complex formation. Using ribosome profiling, we identified selective, phospho-eIF4E-dependent translation of the Wnt signaling pathway in LTP. Surprisingly, the canonical Wnt effector, β-catenin, was massively recruited to the eIF4E cap complex following LTP induction in wild-type, but not Eif4e^S209A, mice. These results demonstrate a critical role for activity-evoked eIF4E phosphorylation in dentate gyrus LTP maintenance, remodeling of the mRNA cap-binding complex, and specific translation of the Wnt pathway.

An Aptamer against MNK1 for Non-Small Cell Lung Cancer Treatment

Lung cancer is the leading cause of cancer-related death worldwide. Its late diagnosis and consequently poor survival make necessary the search for new therapeutic targets. The mitogen-activated protein kinase (MAPK)-interacting kinase 1 (MNK1) is overexpressed in lung cancer and correlates with poor overall survival in non-small cell lung cancer (NSCLC) patients. The previously identified and optimized aptamer from our laboratory against MNK1, apMNKQ2, showed promising results as an antitumor drug in breast cancer in vitro and in vivo. Thus, the present study shows the antitumor potential of apMNKQ2 in another type of cancer where MNK1 plays a significant role, such as NSCLC. The effect of apMNKQ2 in lung cancer was studied with viability, toxicity, clonogenic, migration, invasion, and in vivo efficacy assays. Our results show that apMNKQ2 arrests the cell cycle and reduces viability, colony formation, migration, invasion, and epithelial-mesenchymal transition (EMT) processes in NSCLC cells. In addition, apMNKQ2 reduces tumor growth in an A549-cell line NSCLC xenograft model. In summary, targeting MNK1 with a specific aptamer may provide an innovative strategy for lung cancer treatment.

Overcoming Paradoxical Kinase Priming by a Novel MNK1 Inhibitor

Targeting the kinases MNK1 and MNK2 has emerged as a valuable strategy in oncology. However, most of the advanced inhibitors are acting in an adenosine triphosphate (ATP)-competitive mode, precluding the evaluation of different binding modes in preclinical settings. Using rational design, we identified and validated the 4,6-diaryl-pyrazolo[3,4-b]pyridin-3-amine scaffold as the core for MNK inhibitors. Signaling pathway analysis confirmed a direct effect of the hit compound EB1 on MNKs, and in line with the reported function of these kinases, EB1 only affects the growth of tumor but not normal cells. Molecular modeling revealed the binding of EB1 to the inactive conformation of MNK1 and the interaction with the specific DFD motif. This novel mode of action appears to be superior to the ATP-competitive inhibitors, which render the protein in a pseudo-active state. Overcoming this paradoxical activation of MNKs by EB1 represents therefore a promising starting point for the development of a novel generation of MNK inhibitors.

High-throughput translational profiling with riboPLATE-seq

Protein synthesis is dysregulated in many diseases, but we lack a systems-level picture of how signaling molecules and RNA binding proteins interact with the translational machinery, largely due to technological limitations. Here we present riboPLATE-seq, a scalable method for generating paired libraries of ribosome-associated and total mRNA. As an extension of the PLATE-seq protocol, riboPLATE-seq utilizes barcoded primers for pooled library preparation, but additionally leverages anti-rRNA ribosome immunoprecipitation on whole polysomes to measure ribosome association (RA). We compare RA to its analogue in ribosome profiling and RNA sequencing, translation efficiency, and demonstrate both the performance of riboPLATE-seq and its utility in detecting translational alterations induced by specific inhibitors of protein kinases.

The molecular view of mechanical stress of brain cells, local translation, and neurodegenerative diseases

The assumption that chronic mechanical stress in brain cells stemming from intracranial hypertension, arterial hypertension, or mechanical injury is a risk factor for neurodegenerative diseases was put forward in the 1990s and has since been supported. However, the molecular mechanisms that underlie the way from cell exposure to mechanical stress to disturbances in synaptic plasticity followed by changes in behavior, cognition, and memory are still poorly understood. Here we review (1) the current knowledge of molecular mechanisms regulating local translation and the actin cytoskeleton state at an activated synapse, where they play a key role in the formation of various sorts of synaptic plasticity and long-term memory, and (2) possible pathways of mechanical stress intervention. The roles of the mTOR (mammalian target of rapamycin) signaling pathway; the RNA-binding FMRP protein; the CYFIP1 protein, interacting with FMRP; the family of small GTPases; and the WAVE regulatory complex in the regulation of translation initiation and actin cytoskeleton rearrangements in dendritic spines of the activated synapse are discussed. Evidence is provided that chronic mechanical stress may result in aberrant activation of mTOR signaling and the WAVE regulatory complex via the YAP/TAZ system, the key sensor of mechanical signals, and influence the associated pathways regulating the formation of F actin filaments and the dendritic spine structure. These consequences may be a risk factor for various neurological conditions, including autistic spectrum disorders and epileptic encephalopathy. In further consideration of the role of the local translation system in the development of neuropsychic and neurodegenerative diseases, an original hypothesis was put forward that one of the possible causes of synaptopathies is impaired proteome stability associated with mTOR hyperactivity and formation of complex dynamic modes of de novo protein synthesis in response to synapse-stimulating factors, including chronic mechanical stress.

Dynamic m6A mRNA Methylation Reveals the Role of METTL3/14-m6A-MNK2-ERK Signaling Axis in Skeletal Muscle Differentiation and Regeneration

N⁶-methyladenosine (m⁶A) RNA methylation has emerged as an important factor in various biological processes by regulating gene expression. However, the dynamic profile, function and underlying molecular mechanism of m⁶A modification during skeletal myogenesis remain elusive. Here, we report that members of the m⁶A core methyltransferase complex, METTL3 and METTL14, are downregulated during skeletal muscle development. Overexpression of either METTL3 or METTL14 dramatically blocks myotubes formation. Correspondingly, knockdown of METTL3 or METTL14 accelerates the differentiation of skeletal muscle cells. Genome-wide transcriptome analysis suggests ERK/MAPK is the downstream signaling pathway that is regulated to the greatest extent by METTL3/METTL14. Indeed, METTL3/METTL14 expression facilitates ERK/MAPK signaling. Via MeRIP-seq, we found that MNK2, a critical regulator of ERK/MAPK signaling, is m⁶A modified and is a direct target of METTL3/METTL14. We further revealed that YTHDF1 is a potential reader of m⁶A on MNK2, regulating MNK2 protein levels without affecting mRNA levels. Furthermore, we discovered that METTL3/14-MNK2 axis was up-regulated notably after acute skeletal muscle injury. Collectively, our studies revealed that the m⁶A writers METTL3/METTL14 and the m⁶A reader YTHDF1 orchestrate MNK2 expression posttranscriptionally and thus control ERK signaling, which is required for the maintenance of muscle myogenesis and may contribute to regeneration.

Update on the Development of MNK Inhibitors as Therapeutic Agents

Mitogen-activated protein kinase-interacting kinases 1 and 2 (MNK1/2) represent a central class of enzymes that are activated by extracellular signal-regulated kinase (ERK) or p38 mitogen-activated protein (MAP) kinases. MNK1 and MNK2 coordinate cellular signaling, control production of inflammatory chemokines, and regulate cell proliferation and survival. MNK1/2 are referred to as serine/threonine kinases as they phosphorylate serine or threonine residues on their substrates. Upon activation, MNK1/2 phosphorylate eukaryotic translation initiation factor 4E (eIF4E) at Ser209, which in turn initiates ribosome assembly and protein translation. Deleterious overexpression of MNK1/2 and/or eIF4E have been reported in several diseases including cancers, neurological disorders, autism, and inflammation. Recently, there have been intense efforts toward the development of potent and selective inhibitors of MNK1/2 in both academia and industry. Herein, we review the current understanding of the structural and biological aspects of MNK1/2 and provide an update of pharmacological inhibitors of MNK1/2 including candidates in clinical trials.

Inhibitory effects of Tomivosertib in acute myeloid leukemia

The MAPK-interacting kinases 1 and 2 (MNK1/2) have generated increasing interest as therapeutic targets for acute myeloid leukemia (AML). We evaluated the therapeutic potential of the highly-selective MNK1/2 inhibitor Tomivosertib on AML cells. Tomivosertib was highly effective at blocking eIF4E phosphorylation on serine 209 in AML cells. Such inhibitory effects correlated with dose-dependent suppression of cellular viability and leukemic progenitor colony formation. Moreover, combination of Tomivosertib and Venetoclax resulted in synergistic anti-leukemic responses in AML cell lines. Mass spectrometry studies identified novel putative MNK1/2 interactors, while in parallel studies we demonstrated that MNK2 - RAPTOR - mTOR complexes are not disrupted by Tomivosertib. Overall, these findings demonstrate that Tomivosertib exhibits potent anti-leukemic properties on AML cells and support the development of clinical translational efforts involving the use of this drug, alone or in combination with other therapies for the treatment of AML.

Progress in developing MNK inhibitors

The MNKs (mitogen-activated protein kinase-interacting protein kinases) phosphorylate eIF4E (eukaryotic initiation factor 4 E) at serine 209; eIF4E plays an important role in the translation of cytoplasmic mRNAs, all of which possess a 5' 'cap' structure to which eIF4E binds. Elevated levels of eIF4E, p-eIF4E and/or the MNK protein kinases have been found in many types of cancer, including solid tumors and leukemia. MNKs also play a role in metabolic disease. Regulation of the activities of MNKs (MNK1 and MNK2), control the phosphorylation of eIF4E, which in turn has a close relationship with the processes of tumor development, cell migration and invasion, and energy metabolism. MNK knock-out mice display no adverse effects on normal cells or phenotypes suggesting that MNK may be a potentially safe targets for the treatment of various cancers. Several MNK inhibitors or 'degraders' have been identified. Initially, some of the inhibitors were developed from natural products or based on other protein kinase inhibitors which inhibit multiple kinases. Subsequently, more potent and selective inhibitors for MNK1/2 have been designed and synthesized. Currently, three inhibitors (BAY1143269, eFT508 and ETC-206) are in various stages of clinical trials for the treatment of solid cancers or leukemia, either alone or combined with inhibitors of other protein kinase. In this review, we summarize the diverse MNK inhibitors that have been reported in patents and other literature, including those with activities in vitro and/or in vivo.

Reciprocal signaling between mTORC1 and MNK2 controls cell growth and oncogenesis

eIF4E plays key roles in protein synthesis and tumorigenesis. It is phosphorylated by the kinases MNK1 and MNK2. Binding of MNKs to eIF4G enhances their ability to phosphorylate eIF4E. Here, we show that mTORC1, a key regulator of mRNA translation and oncogenesis, directly phosphorylates MNK2 on Ser74. This suppresses MNK2 activity and impairs binding of MNK2 to eIF4G. These effects provide a novel mechanism by which mTORC1 signaling impairs the function of MNK2 and thereby decreases eIF4E phosphorylation. MNK2[S74A] knock-in cells show enhanced phosphorylation of eIF4E and S6K1 (i.e., increased mTORC1 signaling), enlarged cell size, and increased invasive and transformative capacities. MNK2[Ser74] phosphorylation was inversely correlated with disease progression in human prostate tumors. MNK inhibition exerted anti-proliferative effects in prostate cancer cells in vitro. These findings define a novel feedback loop whereby mTORC1 represses MNK2 activity and oncogenic signaling through eIF4E phosphorylation, allowing reciprocal regulation of these two oncogenic pathways.

Genome-wide translation patterns in gliomas: An integrative view

Gliomas are the most frequent tumors of the central nervous system (CNS) and include the highly malignant glioblastoma (GBM). Characteristically, gliomas have translational control deregulation related to overactivation of signaling pathways such as PI3K/AKT/mTORC1 and Ras/ERK1/2. Thus, mRNA translation appears to play a dominant role in glioma gene expression patterns. The, analysis of genome-wide translated transcripts, together known as the translatome, may reveal important information for understanding gene expression patterns in gliomas. This review provides a brief overview of translational control mechanisms altered in gliomas with a focus on the current knowledge related to the translatomes of glioma cells and murine glioma models. We present an integrative meta-analysis of selected glioma translatome data with the aim of identifying recurrent patterns of gene expression preferentially regulated at the level of translation and obtaining clues regarding the pathological significance of these alterations. Re-analysis of several translatome datasets was performed to compare the translatomes of glioma models with those of their non-tumor counterparts and to document glioma cell responses to radiotherapy and MNK modulation. The role of recurrently altered genes in the context of translational control and tumorigenesis are discussed.

Spatial organization and crosstalk of vimentin and actin stress fibers regulate the osteogenic differentiation of human adipose-derived stem cells

Human adipose-derived stem cells (hASCs) are ideal seed cells for tissue engineering due to their multidirectional differentiation potential. Microfilaments, microtubules, and intermediate filaments are responsible for supporting the intracellular space. Vimentin, a type III intermediate filament protein that is specifically expressed in cells of mesenchymal origin, can function as a scaffold and endow cells with tension and shear stress resistance. Actin stress fibers (ASF) act as an important physical device in stress signal transduction, providing stiffness for cells, and promoting osteogenesis. Through direct physical contact, cross-linkers, and spatial interactions, vimentin and actin networks exist as intersecting entities. Spatial interactions occur in the overlapping area of cytoskeleton subsystems, which could affect cell morphology, cell mechanics, and cell fate. However, how does the spatial organization between the cytoskeletal subsystems changed during osteogenesis, especially between vimentin and ASF, is still not understood, and its mechanism effect on cell fate remains unclear. In our study, WB experiment was used to detect the expression changes in Vimentin, ASF, and other proteins. Cells were reconstructed by three-dimensional scanning with fluorescence microscope, and the spatial thickness of vimentin and ASF cytoskeletons and the thickness of the overlapping area between them were calculated, respectively, so as to observe the spatial reorganization of vimentin and ASF in cells. Cytochalasin D (an inhibitor of actin polymerization) and vimentin upregulated/downregulated cells were used to verify the change in the spatial organization between vimentin and ASF and its influence on osteogenesis. Then, heat shock protein 27 (HSP27) was downregulated to illuminate the regulatory mechanisms of spatial organization between vimentin and ASF during osteogenesis. The amounts and the spatial positions of vimentin and actin stress fiber exhibited opposite trends during osteogenesis. Through controlling the anchor sites on the nucleus, intermediate filaments vimentin can reduce the spatial proportion of actin stress fibers, which can be regulated by HSP27. In addition, depolymerization of actin stress fibers lead to lower osteogenic differentiation ability, resulting in osteogenesis and lipogenesis existed simultaneously, that can be resisted by vimentin. Our data indicate that the spatial reorganization of vimentin and actin stress fibers is a key factor in the regulation of the differentiation state of hASCs. And their spatial overlapping area is detrimental to hASCs osteogenesis, providing a new perspective for further exploring the mechanism underlying hASCs osteogenesis.

Disabling MNK protein kinases promotes oxidative metabolism and protects against diet-induced obesity

Objectives

Diet-driven obesity is increasingly widespread. Its consequences pose major challenges to human health and health care systems. There are MAP kinase-interacting kinases (MNKs) in mice, MNK1 and MNK2. Studies have demonstrated that mice lacking either MNK1 or MNK2 were partially protected against high-fat diet (HFD)-induced weight gain and insulin resistance. The aims of this study were to evaluate the phenotype of mice lacking both MNKs when given an HFD, to assess whether pharmacological inhibition of MNK function also protects against diet-induced obesity (DIO) and its consequences and to probe the mechanisms underlying such protection.

Methods

Male wild-type (WT) C57Bl6 mice or mice lacking both MNK1 and MNK2 (double knockout, DKO) were fed an HFD or control diet (CD) for up to 16 weeks.

In a separate study, WT mice were also given an HFD for 6 weeks, after which half were treated with the recently-developed MNK inhibitor ETC-206 daily for 10 more weeks while continuing an HFD. Metabolites and other parameters were measured, and the expression of selected mRNAs and proteins was assessed.

Results

MNK-DKO mice were almost completely protected from HFD-induced obesity. Higher energy expenditure (EE) in MNK-DKO mice was observed, which probably reflects the changes in a number of genes or proteins linked to lipolysis, mitochondrial function/biogenesis, oxidative metabolism, and/or ATP consumption. The MNK inhibitor ETC-206 also prevented HFD-induced weight gain, confirming that the activity of the MNKs facilitates weight gain due to excessive caloric consumption.

Conclusions

Disabling MNKs in mice, either genetically or pharmacologically, strongly prevents weight gain on a calorie-rich diet. This finding likely results from increased energy utilisation, involving greater ATP consumption, mitochondrial oxidative metabolism, and other processes.

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Knockout of MNK1/MNK2 protects mice against diet-induced obesity.

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MNK1/2 DKO mice have higher energy expenditure.

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MNK1/2 DKO increases the expression of genes of lipid and mitochondrial metabolism.

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Pharmacological inhibition of MNKs has similar effects.

Novel FMRP interaction networks linked to cellular stress

Silencing of the fragile X mental retardation 1 (FMR1) gene and consequently lack of synthesis of FMR protein (FMRP) are associated with fragile X syndrome, which is one of the most prevalent inherited intellectual disabilities, with additional roles in increased viral infection, liver disease, and reduced cancer risk. FMRP plays critical roles in chromatin dynamics, RNA binding, mRNA transport, and mRNA translation. However, the underlying molecular mechanisms, including the (sub)cellular FMRP protein networks, remain elusive. Here, we employed affinity pull-down and quantitative LC-MS/MS analyses with FMRP. We identified known and novel candidate FMRP-binding proteins as well as protein complexes. FMRP interacted with 180 proteins, 28 of which interacted with its N terminus. Interaction with the C terminus of FMRP was observed for 102 proteins, and 48 proteins interacted with both termini. This FMRP interactome comprises known FMRP-binding proteins, including the ribosomal proteins FXR1P, NUFIP2, Caprin-1, and numerous novel FMRP candidate interacting proteins that localize to different subcellular compartments, including CARF, LARP1, LEO1, NOG2, G3BP1, NONO, NPM1, SKIP, SND1, SQSTM1, and TRIM28. Our data considerably expand the protein and RNA interaction networks of FMRP, which thereby suggest that, in addition to its known functions, FMRP participates in transcription, RNA metabolism, ribonucleoprotein stress granule formation, translation, DNA damage response, chromatin dynamics, cell cycle regulation, ribosome biogenesis, miRNA biogenesis, and mitochondrial organization. Thus, FMRP seems associated with multiple cellular processes both under normal and cell stress conditions in neuronal as well as non-neuronal cell types, as exemplified by its role in the formation of stress granules.

Antimetastatic Effects of Sesamin on Human Head and Neck Squamous Cell Carcinoma through Regulation of Matrix Metalloproteinase-2

Background: Sesamin is a lignin present in sesame oil from the bark of Zanthoxylum spp. Sesamin reportedly has anticarcinogenic potential and exerts anti-inflammatory effects on several tumors. Hypothesis/Purpose: However, the effect of sesamin on metastatic progression in human head and neck squamous carcinoma (HNSCC) remains unknown in vitro and in vivo; hence, we investigated the effect of sesamin on HNSCC cells in vitro. Methods and Results: Sesamin-treated human oral cancer cell lines FaDu, HSC-3, and Ca9-22 were subjected to a wound-healing assay. Furthermore, Western blotting was performed to assess the effect of sesamin on the expression levels of matrix metalloproteinase (MMP)-2 and proteins of the MAPK signaling pathway, including p-ERK1/2, P-p38, and p-JNK1/2. In addition, we investigated the association between MMP-2 expression and the MAPK pathway in sesamin-treated oral cancer cells. Sesamin inhibited cell migration and invasion in FaDu, Ca9-22, and HSC-3 cells and suppressed MMP-2 at noncytotoxic concentrations (0 to 40 μM). Furthermore, sesamin significantly reduced p38 MAPK and JNK phosphorylation in a dose-dependent manner in FaDu and HSC-3 cells. Conclusions: These results indicate that sesamin suppresses the migration and invasion of HNSCC cells by regulating MMP-2 and is thus a potential antimetastatic agent for treating HNSCC.

Deeping in the Role of the MAP-Kinases Interacting Kinases (MNKs) in Cancer

The mitogen-activated protein kinase (MAPK)-interacting kinases (MNKs) are involved in oncogenic transformation and can promote metastasis and tumor progression. In human cells, there are four MNKs isoforms (MNK1a/b and MNK2a/b), derived from two genes by alternative splicing. These kinases play an important role controlling the expression of specific proteins involved in cell cycle, cell survival and cell motility via eukaryotic initiation factor 4E (eIF4E) regulation, but also through other substrates such as heterogeneous nuclear ribonucleoprotein A1, polypyrimidine tract-binding protein-associated splicing factor and Sprouty 2. In this review, we provide an overview of the role of MNK in human cancers, describing the studies conducted to date to elucidate the mechanism involved in the action of MNKs, as well as the development of MNK inhibitors in different hematological cancers and solid tumors.

Distribution and Expression of Vimentin and Desmin in Broiler Pectoralis major Affected by the Growth-Related Muscular Abnormalities

Desmin (DES) and Vimentin (VIM) exert an essential role in maintaining muscle cytoarchitecture and since are considered reliable markers for muscle regeneration, their expression has been extensively investigated in dystrophic muscles. Thus, exhibiting features similar to those of human dystrophic muscles, the present study aimed at assessing the distribution of VIM and DES proteins and the expression of the corresponding genes in Pectoralis major muscles affected by white striping (WS), wooden breast (WB), and spaghetti meat (SM) abnormalities as well as in those having macroscopically normal appearance (NORM). For this purpose, 20 Pectoralis major muscles (5/group) were collected from the same flock of fast-growing broilers to perform immunohistochemistry, immunoblotting and gene expression. Immunohistochemical analyses showed an increased number of fibers immunoreactive to both VIM and DES in WS and WB, while only a few immunoreactive fibers were observed in NORM. Concerning the protein level, if compared with NORM, a 55% increase in VIM content was found in WB affected cases (P < 0.05) thus suggesting the development of intense regenerative processes in an early-stage within these muscles. The significantly higher amount of DES (+53%) found in WS might be attributed to a progression of the regenerative processes that require its synthesis to preserve the structural organization of the developing fibers. On the other hand, significantly lower VIM and DES contents were found in SM. About gene expression, VIM mRNA levels gradually increased from the NORM to the SM group, with significantly higher gene expressions in WB and SM samples compared to the NORM group (P = 0.009 for WB vs. NORM and P = 0.004 for SM vs. NORM). Similarly, the expression of DES gene showed an increase from the NORM to WB group (P = 0.05). Overall, the findings of the present study suggest that intense regenerative processes take place in both WB and WS muscles although a different progression of regeneration might be hypothesized. On the other hand, the lack of correspondence between VIM gene expression and its protein product observed in SM suggests that VIM may also exert a role in the development of the SM phenotype.

Phosphorylation and Signal Transduction Pathways in Translational Control

Protein synthesis, including the translation of specific messenger RNAs (mRNAs), is regulated by extracellular stimuli such as hormones and by the levels of certain nutrients within cells. This control involves several well-understood signaling pathways and protein kinases, which regulate the phosphorylation of proteins that control the translational machinery. These pathways include the mechanistic target of rapamycin complex 1 (mTORC1), its downstream effectors, and the mitogen-activated protein (MAP) kinase (extracellular ligand-regulated kinase [ERK]) signaling pathway. This review describes the regulatory mechanisms that control translation initiation and elongation factors, in particular the effects of phosphorylation on their interactions or activities. It also discusses current knowledge concerning the impact of these control systems on the translation of specific mRNAs or subsets of mRNAs, both in physiological processes and in diseases such as cancer.

Impact of eIF4E phosphorylation at Ser209 via MNK2a on tumour recurrence after curative surgery in localized clear cell renal cell carcinoma

Background: We investigated the roles of eIF4E phosphorylation (Ser209) in tumour recurrence after curative nephrectomy for localized clear cell renal cell carcinoma (ccRCC).

Methods: Expression of eIF4E, p eIF4E and MNKs (MAPK interacting kinases), was evaluated in surgical specimens obtained from consecutive non metastatic ccRCC patients (n = 290) by immunohistochemistry (IHC), immunoblotting, and qRT PCR at the protein and mRNA levels. In human RCC cell lines, the effects of eIF4E phosphorylation were examined using immunoblotting, proliferation, migration and invasion assays with pharmacological inhibitors (CGP57380 or ETP45835) and specific small interfering (si) RNAs against MNK1/2(a/b).

Results: In postoperative follow-up (median, 7.9 y), 40 patients experienced metastatic recurrence. In multivariate Cox analyses, higher IHC expression of p eIF4E in ccRCC significantly predicted a longer recurrence-free interval. eIF4E is phosphorylated mainly by MNK2a in tumour specimens and cell lines. In 786-O and A-498 cell lines, pharmacological inhibition of MNKs decreased p-eIF4E and increased vimentin and N cadherin but did not influence proliferation. Similarly, MNK2 or MNK2a inhibition with siRNA reduced p-eIF4E and enhanced vimentin translation, cell migration and invasion in the cell lines.

Conclusions: MNK2a-induced eIF4E phosphorylation may suppress metastatic recurrence of ccRCC, partially due to vimentin downregulation at the translational level, consequently leading to inhibition of epithelial–mesenchymal transition.

MNK1/NODAL Signaling Promotes Invasive Progression of Breast Ductal Carcinoma In Situ

The mechanisms by which breast cancers progress from relatively indolent ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) are not well understood. However, this process is critical to the acquisition of metastatic potential. MAPK-interacting serine/threonine-protein kinase 1 (MNK1) signaling can promote cell invasion. NODAL, a morphogen essential for embryogenic patterning, is often reexpressed in breast cancer. Here we describe a MNK1/NODAL signaling axis that promotes DCIS progression to IDC. We generated MNK1 knockout (KO) or constitutively active MNK1 (caMNK1)-expressing human MCF-10A-derived DCIS cell lines, which were orthotopically injected into the mammary glands of mice. Loss of MNK1 repressed NODAL expression, inhibited DCIS to IDC conversion, and decreased tumor relapse and metastasis. Conversely, caMNK1 induced NODAL expression and promoted IDC. The MNK1/NODAL axis promoted cancer stem cell properties and invasion in vitro. The MNK1/2 inhibitor SEL201 blocked DCIS progression to invasive disease in vivo. In clinical samples, IDC and DCIS with microinvasion expressed higher levels of phospho-MNK1 and NODAL versus low-grade (invasion-free) DCIS. Cumulatively, our data support further development of MNK1 inhibitors as therapeutics for preventing invasive disease. SIGNIFICANCE: These findings provide new mechanistic insight into progression of ductal carcinoma and support clinical application of MNK1 inhibitors to delay progression of indolent ductal carcinoma in situ to invasive ductal carcinoma.

Effect of disease-associated SLC9A9 mutations on protein-protein interaction networks: implications for molecular mechanisms for ADHD and autism

Na⁺/H⁺ Exchanger 9 (NHE9) is an endosomal membrane protein encoded by the Solute Carrier 9A, member 9 gene (SLC9A9). SLC9A9 has been implicated in attention deficit hyperactivity disorder (ADHD), autism spectrum disorders (ASDs), epilepsy, multiple sclerosis and cancers. To better understand the function of NHE9 and the effects of disease-associated variants on protein-protein interactions, we conducted a quantitative analysis of the NHE9 interactome using co-immunoprecipitation and isobaric labeling-based quantitative mass spectrometry. We identified 100 proteins that interact with NHE9. These proteins were enriched in known functional pathways for NHE9: the endocytosis, protein ubiquitination and phagosome pathways, as well as some novel pathways including oxidative stress, mitochondrial dysfunction, mTOR signaling, cell death and RNA processing pathways. An ADHD-associated mutation (A409P) significantly altered NHE9's interactions with a subset of proteins involved in caveolae-mediated endocytosis and MAP2K2-mediated downstream signaling. An ASD nonsense mutation in SLC9A9, R423X, produced no-detectable amount of NHE9, suggesting the overall loss of NHE9 functional networks. In addition, seven of the NHE9 interactors are products of known autism candidate genes (Simons Foundation Autism Research Initiative, SFARI Gene) and 90% of the NHE9 interactome overlap with SFARI protein interaction network PIN (p < 0.0001), supporting the role of NHE9 interactome in ASDs molecular mechanisms. Our results provide a detailed understanding of the functions of protein NHE9 and its disrupted interactions, possibly underlying ADHD and ASDs. Furthermore, our methodological framework proved useful for functional characterization of disease-associated genetic variants and suggestion of druggable targets.

Cisplatin Synergistically Enhances Antitumor Potency of Conditionally Replicating Adenovirus via p53 Dependent or Independent Pathways in Human Lung Carcinoma

Cisplatin is ranked as one of the most powerful and commonly prescribed anti-tumor chemotherapeutic agents which improve survival in many solid tumors including non-small cell lung cancer. However, the treatment of advanced lung cancer is restricted due to chemotherapy resistance. Here, we developed and investigated survivin promoter regulating conditionally replicating adenovirus (CRAd) for its anti-tumor potential alone or in combination with cisplatin in two lung cancer cells, H23, H2126, and their resistant cells, H23/CPR, H2126/CPR. To measure the expression of genes which regulate resistance, adenoviral transduction, metastasis, and apoptosis in cancer cells, RT-PCR and Western blotting were performed. The anti-tumor efficacy of the treatments was evaluated through flow cytometry, MTT and transwell assays. This study demonstrated that co-treatment with cisplatin and CRAd exerts synergistic anti-tumor effects on chemotherapy sensitive lung cancer cells and monotherapy of CRAd could be a practical approach to deal with chemotherapy resistance. Combined treatment induced stronger apoptosis by suppressing the anti-apoptotic molecule Bcl-2, and reversed epithelial to mesenchymal transition. In conclusion, cisplatin synergistically increased the tumor-killing of CRAd by (1) increasing CRAd transduction via enhanced CAR expression and (2) increasing p53 dependent or independent apoptosis of lung cancer cell lines. Also, CRAd alone proved to be a very efficient anti-tumor agent in cancer cells resistant to cisplatin owing to upregulated CAR levels. In an exciting outcome, we have revealed novel therapeutic opportunities to exploit intrinsic and acquired resistance to enhance the therapeutic index of anti-tumor treatment in lung cancer.

The Novel Mnk1/2 Degrader and Apoptosis Inducer VNLG-152 Potently Inhibits TNBC Tumor Growth and Metastasis

Currently, there are no effective therapies for patients with triple-negative breast cancer (TNBC), an aggressive and highly metastatic disease. Activation of eukaryotic initiation factor 4E (eIF4E) by mitogen-activated protein kinase (MAPK)-interacting kinases 1 and 2 (Mnk1/2) play a critical role in the development, progression and metastasis of TNBC. Herein, we undertook a comprehensive study to evaluate the activity of a first-in-class Mnk1/2 protein degraders, racemic VNLG-152R and its two enantiomers (VNLG-152E1 and VNLG-152E2) in in vitro and in vivo models of TNBC. These studies enabled us to identify racemic VNLG-152R as the most efficacious Mnk1/2 degrader, superior to its pure enantiomers. By targeting Mnk1/2 protein degradation (activity), VNLG-152R potently inhibited both Mnk-eIF4E and mTORC1 signaling pathways and strongly regulated downstream factors involved in cell cycle regulation, apoptosis, pro-inflammatory cytokines/chemokines secretion, epithelial-mesenchymal transition (EMT) and metastasis. Most importantly, orally bioavailable VNLG-152R exhibited remarkable antitumor (91 to 100% growth inhibition) and antimetastatic (~80% inhibition) activities against cell line and patient-derived TNBC xenograft models, with no apparent host toxicity. Collectively, these studies demonstrate that targeting Mnk-eIF4E/mTORC1 signaling with a potent Mnk1/2 degrader, VNLG-152R, is a novel therapeutic strategy that can be developed as monotherapy for the effective treatment of patients with primary/metastatic TNBC.

Design, synthesis and activity of Mnk1 and Mnk2 selective inhibitors containing thieno[2,3-d]pyrimidine scaffold

The mitogen-activated protein kinase-interacting kinases 1 and 2 (MNK1 and MNK2) phosphorylate eukaryotic initiation factor 4E (eIF4E) and play important roles in promoting tumorigenesis and metabolic disease. Thus, inhibiting these enzymes might be valuable in the treatment of such conditions. We designed and synthesized a series of 4-((4-fluoro-2-isopropoxyphenyl)amino)-5-methylthieno[2,3-d]pyrimidine derivatives, and evaluated their inhibitory activity against the MNKs. We found 15 compounds that were active as MNK inhibitors and that one in particular, designated MNK-7g, which was potent against MNK1 and substantially more potent against MNK2. The compound MNK-7g did not affect other signaling pathways tested and had no adverse effects on cell viability. As expected from earlier studies, MNK-7g also inhibited cell migration. Therefore, the compound MNK-7g, which forms an ionic bond with Asp226 in MNK2 and possesses a substituted aniline in a thieno[2,3-d] pyrimidine structure, is a promising starting point for the future development of novel drugs for treating or managing cancer and metabolic disease.

Probing the Anticancer Action of Novel Ferrocene Analogues of MNK Inhibitors

Two novel ferrocene-containing compounds based upon a known MNK1/2 kinase (MAPK-interacting kinase) inhibitor have been synthesized. The compounds were designed to use the unique shape of ferrocene to exploit a large hydrophobic pocket in MNK1/2 that is only partially occupied by the original compound. Screening of the ferrocene analogues showed that both exhibited potent anticancer effects in several breast cancer and AML (acute myeloid leukemia) cell lines, despite a loss of MNK potency. The most potent ferrocene-based compound 5 was further analysed in vitro in MDA-MB-231 (triple negative breast cancer cells). Dose–response curves of compound 5 for 2D assay and 3D assay generated IC₅₀ values (half maximal inhibitory concentration) of 0.55 µM and 1.25 µM, respectively.

Phosphokinome Analysis of Barth Syndrome Lymphoblasts Identify Novel Targets in the Pathophysiology of the Disease

Barth Syndrome (BTHS) is a rare X-linked genetic disease in which the specific biochemical deficit is a reduction in the mitochondrial phospholipid cardiolipin (CL) as a result of a mutation in the CL transacylase tafazzin. We compared the phosphokinome profile in Epstein-Barr-virus-transformed lymphoblasts prepared from a BTHS patient with that of an age-matched control individual. As expected, mass spectrometry analysis revealed a significant (>90%) reduction in CL in BTHS lymphoblasts compared to controls. In addition, increased oxidized phosphatidylcholine (oxPC) and phosphatidylethanolamine (PE) levels were observed in BTHS lymphoblasts compared to control. Given the broad shifts in metabolism associated with BTHS, we hypothesized that marked differences in posttranslational modifications such as phosphorylation would be present in the lymphoblast cells of a BTHS patient. Phosphokinome analysis revealed striking differences in the phosphorylation levels of phosphoproteins in BTHS lymphoblasts compared to control cells. Some phosphorylated proteins, for example, adenosine monophosphate kinase, have been previously validated as bonafide modified phosphorylation targets observed in tafazzin deficiency or under conditions of reduced cellular CL. Thus, we report multiple novel phosphokinome targets in BTHS lymphoblasts and hypothesize that alteration in the phosphokinome profile may provide insight into the pathophysiology of BTHS and potential therapeutic targets.

Transcriptome analysis of Pacific white shrimp (Litopenaeus vannamei) challenged by Vibrio parahaemolyticus reveals unique immune-related genes

Pacific white shrimp (Litopenaeus vannamei) is an important cultural species worldwide. However, Vibrio spp. infections have caused a great economic loss in Pacific white shrimp culture industry. The immune responses of Pacific white shrimp to the Vibrio spp. is not fully characterized. In this study, the transcriptomic profiles of L. vannamei hemocytes were explored by injecting with or without Vibrio parahaemolyticus. Totally, 42,632 high-quality unigenes were obtained from RNAseq data. Comparative genome analysis showed 2258 differentially expressed genes (DEGs) following the Vibrio challenge, including 1017 up-regulated and 1241 down-regulated genes. Eight DEGs were randomly selected for further validation by quantitative real-time RT-PCR (qRT-PCR) and the results showed that are consistent with the RNA-seq data. Due to the lack of predictable adaptive immunity, shrimps rely on an innate immune system to defend themselves against invading microbes by recognizing and clearing them through humoral and cellular immune responses. Here we focused our studies on the humoral immunity, five genes (SR, MNK, CTL3, GILT, and ALFP) were selected from the transcriptomic data, which were significantly up-regulated by V. parahaemolyticus infection. These genes were widely expressed in six different tissues and were up-regulated by both Gram negative bacteria (V. parahaemolyticus) and Gram positive bacteria (Staphylococcus aureus). To further extend our studies, we knock-down those five genes by dsRNA in L. vannamei and analyzed the functions of specific genes against V. parahaemolyticus and S. aureus by bacterial clearance analysis. We found that the ability of L. vannamei was significantly reduced in bacterial clearance when treated with those specific dsRNA. These results indicate that those five genes play essential roles in antibacterial immunity and have its specific functions against different types of pathogens. The obtained data will shed a new light on the immunity of L. vannamei and pave a new way for fighting against the bacterial infection in Pacific white shrimp.

Signaling Pathways Involved in the Regulation of mRNA Translation

Translation is a key step in the regulation of gene expression and one of the most energy-consuming processes in the cell. In response to various stimuli, multiple signaling pathways converge on the translational machinery to regulate its function. To date, the roles of phosphoinositide 3-kinase (PI3K)/AKT and the mitogen-activated protein kinase (MAPK) pathways in the regulation of translation are among the best understood. Both pathways engage the mechanistic target of rapamycin (mTOR) to regulate a variety of components of the translational machinery. While these pathways regulate protein synthesis in homeostasis, their dysregulation results in aberrant translation leading to human diseases, including diabetes, neurological disorders, and cancer. Here we review the roles of the PI3K/AKT and MAPK pathways in the regulation of mRNA translation. We also highlight additional signaling mechanisms that have recently emerged as regulators of the translational apparatus.

Oncogenic MNK signalling regulates the metastasis suppressor NDRG1

The protein N-myc down-regulated gene 1 (NDRG1) represses tumour metastasis. It is phosphorylated at several sites by serum and glucocorticoid-regulated kinase 1 (SGK1). Here we show that NDRG1 is also regulated by the oncogenic MAP kinase-interacting kinase (MNK) pathway, a target for cancer therapy.Inhibiting MNKs increases the expression of NDRG1 protein and mRNA in breast cancer cells. MNK inhibition also decreases the phosphorylation of NDRG1. Phosphorylation of NDRG1 is reduced in cells lacking MNK1, but not MNK2-knockout cells, indicating that NDRG1 phosphorylation is a specific target for MNK1. However, MNK1 cannot directly phosphorylate NDRG1 in vitro, indicating that additional signalling connections are involved. Taken together, our data indicate that MNK signaling regulates NDRG1 at transcriptional and post-translational levels.We show that SGK1 phosphorylates MNK1 at a conserved site, which represses its activity. NDRG1, SGK1 and the MNKs are implicated in cell migration and metastasis. As expected, knocking-down NDRG1 promoted cell migration. However, whereas MNK inhibition impairs these processes irrespective of NDRG1 levels, SGK inhibition only did so in NDRG1-depleted cells. Thus, MNKs and SGK affect migration/invasion through distinct mechanisms.Our data reveal several novel connections between signalling pathways important for tumour biology.

Vimentin expression is required for the development of EMT-related renal fibrosis following unilateral ureteral obstruction in mice

Most renal transplants ultimately fail secondary to chronic allograft nephropathy (CAN). Vimentin (vim) is a member of the intermediate filament family of proteins and has been shown to be important in the development of CAN. One of the pathways leading to chronic renal fibrosis after transplant is thought to be epithelial to mesenchymal transition (EMT). Even though vim expression is one of the main steps of EMT, it is unknown whether vim expression is required for EMT leading to renal fibrosis and allograft loss. To this end, the role of vim in renal fibrosis was determined via unilateral ureteral obstruction (UUO) in vim knockout mice (129 svs6 vim -/-). Following UUO, kidneys were recovered and analyzed via Western blotting, immunofluorescence, and transcriptomics. Cultured human proximal renal tubular (HK-2) cells were subjected to lentiviral-driven inhibition of vim expression and then treated with transforming growth factor (TGF)-β to undergo EMT. Immunoblotting as well as wound healing assays were used to determine development of EMT. Western blotting analyses of mice undergoing UUO reveal increased levels of vim soon after UUO. As expected, interstitial collagen deposition increased in control mice following UUO but decreased in vim -/- kidneys. Immunofluorescence analyses also revealed altered localization of β-catenin in vim -/- mice undergoing UUO without significant changes in mRNA levels. However, RNA sequencing revealed a decrease in β-catenin-dependent genes in vim -/- kidneys. Finally, vim-silenced HK-2 cell lines undergoing EMT were shown to have decreased cellular migration during wound healing. We conclude that vim inhibition decreases fibrosis following UUO by possibly altering β-catenin localization and downstream signaling.

Synergistic effects of inhibiting the MNK-eIF4E and PI3K/AKT/ mTOR pathways on cell migration in MDA-MB-231 cells

The study of eukaryotic initiation factor 4E (eIF4E) is a key focus in cancer research due to its role in controlling the translation of tumour-associated proteins, that drive an aggressive migratory phenotype. eIF4E is a limiting component of the eIF4F complex which is a critical determinant for the translation of mRNAs. Mitogen-activated protein kinase interacting protein kinases (MNK1/2) phosphorylate eIF4E on Ser209, promoting the expression of oncogenic proteins, whereas mTORC1 phosphorylates and de-activates the eIF4E inhibitor, 4E-BP1, to release translational repression. Here we show that inhibiting these pathways simultaneously effectively slows the rate of cell migration in breast cancer cells. However, a molecular hybridisation approach using novel, cleavable dual MNK1/2 and PI3K/mTOR inhibiting hybrid agents was less effective at slowing cell migration.

Eukaryotic elongation factor 2 kinase upregulates the expression of proteins implicated in cell migration and cancer cell metastasis

Eukaryotic elongation factor 2 kinase (eEF2K) negatively regulates the elongation phase of mRNA translation and hence protein synthesis. Increasing evidence indicates that eEF2K plays an important role in the survival and migration of cancer cells and in tumor progression. As demonstrated by two-dimensional wound-healing and three-dimensional transwell invasion assays, knocking down or inhibiting eEF2K in cancer cells impairs migration and invasion of cancer cells. Conversely, exogenous expression of eEF2K or knocking down eEF2 (the substrate of eEF2K) accelerates wound healing and invasion. Importantly, using LC-HDMS^E analysis, we identify 150 proteins whose expression is decreased and 73 proteins which are increased upon knocking down eEF2K in human lung carcinoma cells. Of interest, 34 downregulated proteins are integrins and other proteins implicated in cell migration, suggesting that inhibiting eEF2K may help prevent cancer cell mobility and metastasis. Interestingly, eEF2K promotes the association of integrin mRNAs with polysomes, providing a mechanism by which eEF2K may enhance their cellular levels. Consistent with this, genetic knock down or pharmacological inhibition of eEF2K reduces the protein expression levels of integrins. Notably, pharmacological or genetic inhibition of eEF2K almost completely blocked tumor growth and effectively prevented the spread of tumor cells in vivo. High levels of eEF2K expression were associated with invasive carcinoma and metastatic tumors. These data provide the evidence that eEF2K is a new potential therapeutic target for preventing tumor metastasis.

Dual abrogation of MNK and mTOR: a novel therapeutic approach for the treatment of aggressive cancers

Targeting the translational machinery has emerged as a promising therapeutic option for cancer treatment. Cancer cells require elevated protein synthesis and exhibit augmented activity to meet the increased metabolic demand. Eukaryotic translation initiation factor 4E is necessary for mRNA translation, its availability and phosphorylation are regulated by the PI3K/AKT/mTOR and MNK1/2 pathways. The phosphorylated form of eIF4E drives the expression of oncogenic proteins including those involved in metastasis. In this article, we will review the role of eIF4E in cancer, its regulation and discuss the benefit of dual inhibition of upstream pathways. The discernible interplay between the MNK and mTOR signaling pathways provides a novel therapeutic opportunity to target aggressive migratory cancers through the development of hybrid molecules.

Translational control and the cancer cell response to stress

The evidence for the importance of aberrant translation in cancer cells is overwhelming. Reflecting the wealth of data, there are excellent reviews delineating how ribosomes and initiation factors are linked to cancer [1-3], and the therapeutic strategies being devised to target them [4]. Changes in translational efficiency can engender a malignant phenotype without the need for chromatin reorganization, transcription, splicing and mRNA export [5,6]. Thus, cancer-related modulations of the translational machinery are ideally suited to allow cancer cells to respond to the various stresses encountered along the path of tumorigenesis and organism-wide dissemination [7^•,8,9,10^•]. Emerging findings supporting this notion are the focus of this review.

Mycobacterium tuberculosis subverts negative regulatory pathways in human macrophages to drive immunopathology

Tuberculosis remains a global pandemic and drives lung matrix destruction to transmit. Whilst pathways driving inflammatory responses in macrophages have been relatively well described, negative regulatory pathways are less well defined. We hypothesised that Mycobacterium tuberculosis (Mtb) specifically targets negative regulatory pathways to augment immunopathology. Inhibition of signalling through the PI3K/AKT/mTORC1 pathway increased matrix metalloproteinase-1 (MMP-1) gene expression and secretion, a collagenase central to TB pathogenesis, and multiple pro-inflammatory cytokines. In patients with confirmed pulmonary TB, PI3Kδ expression was absent within granulomas. Furthermore, Mtb infection suppressed PI3Kδ gene expression in macrophages. Interestingly, inhibition of the MNK pathway, downstream of pro-inflammatory p38 and ERK MAPKs, also increased MMP-1 secretion, whilst suppressing secretion of TH1 cytokines. Cross-talk between the PI3K and MNK pathways was demonstrated at the level of eIF4E phosphorylation. Mtb globally suppressed the MMP-inhibitory pathways in macrophages, reducing levels of mRNAs encoding PI3Kδ, mTORC-1 and MNK-1 via upregulation of miRNAs. Therefore, Mtb disrupts negative regulatory pathways at multiple levels in macrophages to drive a tissue-destructive phenotype that facilitates transmission.

New insights into the regulatory function of CYFIP1 in the context of WAVE- and FMRP-containing complexes

Cytoplasmic FMRP interacting protein 1 (CYFIP1) is a candidate gene for intellectual disability (ID), autism, schizophrenia and epilepsy. It is a member of a family of proteins that is highly conserved during evolution, sharing high homology with its Drosophila homolog, dCYFIP. CYFIP1 interacts with the Fragile X mental retardation protein (FMRP, encoded by the FMR1 gene), whose absence causes Fragile X syndrome, and with the translation initiation factor eIF4E. It is a member of the WAVE regulatory complex (WRC), thus representing a link between translational regulation and the actin cytoskeleton. Here, we present data showing a correlation between mRNA levels of CYFIP1 and other members of the WRC. This suggests a tight regulation of the levels of the WRC members, not only by post-translational mechanisms, as previously hypothesized. Moreover, we studied the impact of loss of function of both CYFIP1 and FMRP on neuronal growth and differentiation in two animal models - fly and mouse. We show that these two proteins antagonize each other's function not only during neuromuscular junction growth in the fly but also during new neuronal differentiation in the olfactory bulb of adult mice. Mechanistically, FMRP and CYFIP1 modulate mTor signaling in an antagonistic manner, likely via independent pathways, supporting the results obtained in mouse as well as in fly at the morphological level. Collectively, our results illustrate a new model to explain the cellular roles of FMRP and CYFIP1 and the molecular significance of their interaction.

Galeterone and VNPT55 disrupt Mnk-eIF4E to inhibit prostate cancer cell migration and invasion

Metastatic castration-resistant prostate cancer (mCRPC) accounts for a high percentage of prostate cancer mortality. The proprietary compound galeterone (gal) was designed to inhibit proliferation of androgen/androgen receptor (AR)-dependent prostate cancer cell in vitro and in vivo and is currently in phase III clinical development. Additionally, clinical studies with gal revealed its superb efficacy in four different cohorts of patients with mCRPC, including those expressing splice variant AR-V7. Preclinical studies with gal show that it also exhibits strong antiproliferative activities against AR-negative prostate cancer cells and tumors through a mechanism involving phosphorylation of eIF2α, which forms an integral component of the eukaryotic mRNA translation complex. Thus, we hypothesized that gal and its new analog, VNPT55, could modulate oncogenic mRNA translation and prostate cancer cell migration and invasion. We report that gal and VNPT55 profoundly inhibit migration and invasion of prostate cancer cells, possibly by down-regulating protein expression of several EMT markers (Snail, Slug, N-cadherin, vimentin, and MMP-2/-9) via antagonizing the Mnk-eIF4E axis. In addition, gal/VNPT55 inhibited both NF-κB and Twist1 transcriptional activities, down-regulating Snail and BMI-1 mRNA expression, respectively. Furthermore, profound up-regulation of E-cadherin mRNA and protein expression may explain the observed significant inhibition of prostate cancer cell migration and invasion. Moreover, expression of self-renewal proteins, β-catenin, CD44, and Nanog, was markedly depleted. Analysis of gal/VNPT55-treated CWR22Rv1 xenograft tissue sections also revealed that observations in vitro were recapitulated in vivo. Our results suggest that gal/VNPT55 could become promising agents for the prevention and/or treatment of all stages of prostate cancer.

Genome-wide gain-of-function screen for genes that induce epithelial-to-mesenchymal transition in breast cancer

Epithelial to mesenchymal transition (EMT) is a developmental program that has been implicated in progression, metastasis and therapeutic resistance of some carcinomas. To identify genes whose overexpression drives EMT, we screened a lentiviral expression library of 17000 human open reading frames (ORFs) using high-content imaging to quantitate cytoplasmic vimentin. Hits capable of increasing vimentin in the mammary carcinoma-derived cell line MDA-MB-468 were confirmed in the non-tumorigenic breast-epithelial cell line MCF10A. When overexpressed in this model, they increased the rate of cell invasion through Matrigel™, induced mesenchymal marker expression and reduced expression of the epithelial marker E-cadherin. In gene-expression datasets derived from breast cancer patients, the expression of several novel genes correlated with expression of known EMT marker genes, indicating their in vivo relevance. As EMT-associated properties are thought to contribute in several ways to cancer progression, genes identified in this study may represent novel targets for anti-cancer therapy.

Tuning Specific Translation in Cancer Metastasis and Synaptic Memory: Control at the MNK-eIF4E Axis

The eukaryotic translation initiation factor (eIF) 4E, which binds to the 5'-cap of mRNA, undergoes phosphorylation on a single conserved serine, executed by the mitogen-activated protein kinase (MAPK)-interacting kinases (MNKs). However, the functional consequences and physiological roles of MNK signalling have remained obscure. Now, new pharmacological and genetic tools have provided unprecedented insights into the function of MNKs and eIF4E phosphorylation. The studies suggest that MNKs control the translation of specific mRNAs in cancer metastasis and neuronal synaptic plasticity by a novel mechanism involving the regulation of the translational repressor, cytoplasmic fragile-X protein-interacting protein 1 (CYFIP1). These recent breakthroughs go a long way to resolving the longstanding enigma and controversy surrounding the function of the MNK-eIF4E axis in cancer cell biology and neurobiology.

A unique binding mode of the eukaryotic translation initiation factor 4E for guiding the design of novel peptide inhibitors

The interaction between the eukaryotic translation initiation factor 4E (eIF4E) and eIF4E binding proteins (4E-BP) is a promising template for the inhibition of eIF4E and the treatment of diseases such as cancer and a spectrum of autism disorders, including the Fragile X syndrome (FXS). Here, we report an atomically detailed model of the complex between eIF4E and a peptide fragment of a 4E-BP, the cytoplasmic Fragile X interacting protein (CYFIP1). This model was generated using computer simulations with enhanced sampling from an alchemical replica exchange approach and validated using long molecular dynamics simulations. 4E-BP proteins act as post-transcriptional regulators by binding to eIF4E and preventing mRNA translation. Dysregulation of eIF4E activity has been linked to cancer, FXS, and autism spectrum disorders. Therefore, the study of the mechanism of inhibition of eIF4E by 4E-BPs is key to the development of drug therapies targeting this regulatory pathways. The results obtained in this work indicate that CYFIP1 interacts with eIF4E by an unique mode not shared by other 4E-BP proteins and elucidate the mechanism by which CYFIP1 interacts with eIF4E despite having a sequence binding motif significantly different from most 4E-BPs. Our study suggests an alternative strategy for the design of eIF4E inhibitor peptides with superior potency and specificity than currently available.

MNK1 and MNK2 mediate adverse effects of high-fat feeding in distinct ways

The MAP kinase-interacting kinases (MNK1 and MNK2) are non-essential enzymes which are activated by MAP kinases. They are implicated in controlling protein synthesis. Here we show that mice in which the expression of either MNK1 or MNK2 has been knocked out (KO) are protected against adverse effects of high-fat feeding, and in distinct ways. High-fat diet (HFD)-fed MNK2-KO show less weight gain than wild-type animals, and improved glucose tolerance, better insulin sensitivity and markedly diminished adipose tissue inflammation. This suggests MNK2 plays a role in adipogenesis and/or lipogenesis and in macrophage biology. MNK1-KO/HFD mice show better glucose tolerance and insulin sensitivity, but gain weight and show similar adipose inflammation to WT animals. These data suggest MNK1 participates in mediating HFD-induced insulin resistance. Our findings reveal distinct roles for the MNKs in a novel area of disease biology, metabolic dysfunction, and suggests they are potential new targets for managing metabolic disease.

Characterization of MNK1b DNA Aptamers That Inhibit Proliferation in MDA-MB231 Breast Cancer Cells

Elevated expression levels of eukaryotic initiation factor 4E (eIF4E) promote cancer development and progression. MAP kinase interacting kinases (MNKs) modulate the function of eIF4E through the phosphorylation that is necessary for oncogenic transformation. Therefore, pharmacologic MNK inhibitors may provide a nontoxic and effective anticancer strategy. MNK1b is a truncated isoform of MNK1a that is active in the absence of stimuli. Using in vitro selection, high-affinity DNA aptamers to MNK1b were selected from a library of ssDNA. Selection was monitored using the enzyme-linked oligonucleotide assay (ELONA), and the selected aptamer population was cloned and sequenced. Four groups of aptamers were identified, and the affinities of one representative for rMNK1b were determined using ELONA and quantitative polymerase chain reaction. Two aptamers, named apMNK2F and apMNK3R, had a lower Kd in the nmol/l range. The secondary structure of the selected aptamers was predicted using mFold, and the QGRS Mapper indicated the presence of potential G-quadruplex structures in both aptamers. The selected aptamers were highly specific against MNK1, showing higher affinity to MNK1b than to MNK1a. Interestingly, both aptamers were able to produce significant translation inhibition and prevent tumor cell proliferation and migration and colony formation in breast cancer cells. These results indicate that MNK1 aptamers have an attractive therapeutic potential.

Usnic acid is a novel Pim-1 inhibitor with the abilities of inhibiting growth and inducing apoptosis in human myeloid leukemia cells

Usnic acid, a potent Pim-1 inhibitor, represents a lead compound for developing effective therapeutics for myeloid leukemia treatment.